Examining Rates of Traumatic Events and Posttraumatic Stress Disorder Symptoms Among Autistic Adults

Abstract

Background:

Autistic adults experience high rates of traumatic events and posttraumatic stress disorder (PTSD) symptoms. However, less is known about how autistic adults experience (i.e., by directly experiencing, witnessing, and/or learning about) distinct types of traumatic events (e.g., social, nonsocial traumas). Little research has considered whether the four-factor structure of PTSD symptom domains (e.g., avoidance, intrusions, hypervigilance, negative mood/cognition) can be applied for autistic adults. Lastly, understanding how demographic factors (e.g., gender, race/ethnicity) relate to rates of traumatic events and symptoms among autistic adults is critical for understanding disparities relating to PTSD. Therefore, the current study aims to examine self-reported traumatic events and PTSD symptoms, and identify associations with demographic factors, among autistic adults.

Methods:

Participants included 276 autistic adults and a nationally representative sample of 361 nonautistic adults who completed online measures, including the Life Events Checklist for DSM-5, Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5), Autism-Spectrum Quotient-Short, and Patient Health Questionnaire-4. Analyses focused on evaluating group differences in traumatic events and symptoms and considered associations with demographic factors.

Results:

Autistic adults reported significantly higher rates of directly experiencing, witnessing, and learning about traumatic events than nonautistic adults, including more interpersonal events (e.g., physical assault, sexual assault) and fewer transportation accidents than nonautistic adults. Autistic adults also reported significantly higher levels of all PTSD symptom clusters than nonautistic adults. A confirmatory factor analysis and follow-up invariance analyses of the PCL-5 revealed that the four-factor Diagnostic and Statistical Manual of Mental Health Disorders, Fifth Edition (DSM-5) PTSD symptom subscale structure was equivalent across groups of autistic and nonautistic adults.

Conclusion:

Autistic adults experienced more traumatic events and PTSD symptoms overall, particularly more interpersonal traumas and hyperarousal and negative mood/cognition symptoms than nonautistic adults. Future research should examine outcomes of trauma exposure, identify protective factors, and examine efficacy of trauma-focused treatments for autistic individuals, in partnership with autistic adults.

Community brief

Why is this an important issue?

Autistic people experience more traumatic events and more symptoms of posttraumatic stress disorder (PTSD) than nonautistic people. Little is known about if PTSD symptoms can be measured similarly among autistic and nonautistic people. Studying trauma, PTSD, and how PTSD is measured is helpful for developing useful resources for autistic adults who experience trauma and PTSD.

What was the purpose of this study?

We wanted to compare how autistic adults and nonautistic adults experience traumatic events and symptoms of PTSD.

What did the researchers do?

Two-hundred seventy-six autistic adults and 361 nonautistic adults completed questionnaires through an online research platform. We used the Life Events Checklist for DSM-5 (LEC-5) to ask about traumatic events that adults may have experienced directly, witnessed, learned about, or experienced as part of one's job. We used the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5) to measure PTSD symptoms, including intrusions (thinking about trauma when one does not want to), avoidance (staying away from thoughts or rteminders of trauma), hyperarousal (feeling restless, having difficulty concentrating), and negative thoughts and feelings (feeling depressed, thinking the world is unsafe). Participants also filled out the Autism-Spectrum Quotient-Short to measure autistic traits and the Patient Health Questionnaire-4 to measure depression and anxiety. The researchers looked to see if the PCL-5 questionnaire works differently when it is used by autistic and nonautistic adults.

What were the results of the study?

More traumatic events directly happened to autistic adults than nonautistic adults. Autistic adults also witnessed and learned about more traumatic events. Autistic adults experienced more interpersonal events than non-autistic adults (such as physical assault, sexual assault, other unwanted sexual experiences, and severe human suffering). They experienced fewer transportation accidents than non-autistic adults. Autistic adults had more PTSD symptoms than nonautistic adults, including more overall symptoms and more symptoms in each of the PTSD symptom categories (intrusions, avoidance, hyperarousal, negative thoughts and feelings). Also, the PCL-5 questionnaire measures PTSD symptoms similarly among autistic and nonautistic adults.

What do these findings add to what was already known?

Our results are consistent with other research showing more traumatic events for autistic than non-autistic people, and also show higher rates of seeing or learning about traumatic events. We also contribute new information about using the PCL-5 with autistic adults, which can help clinicians and other researchers.

What are potential weaknesses in the study?

This study only asked autistic adults about traumatic events on the LEC-5, which does not include other traumatic events such as bullying nor sensory trauma. It is possible that autistic adults interpreted the questions differently than non-autistic adults. More than half of our participants were White, so we know less about trauma experiences for autistic people from other racial and ethnic backgrounds.

How will these findings help autistic adults now or in the future?

The findings of this study provide useful information about how autistic adults experience traumatic events and PTSD symptoms, which is important for improving support services for autistic adults.

Introduction

Supporting autistic adults who have experienced trauma is a critical research and clinical priority. One important step in this research is to identify rates of different types of traumatic experiences among autistic adults¹ to further understand which types of events autistic adults most frequently experience and inform personalized prevention and support strategies. An additional growing body of research is the comparison of symptom profiles of posttraumatic stress disorder (PTSD) among autistic and nonautistic adults (see Rumball²). Still, less is known about how distinct PTSD symptom domains (e.g., avoidance vs. intrusions) may differ between autistic and nonautistic adults. Even less is known regarding how demographic factors relate to exposure to traumatic events and symptoms among autistic adults.

Therefore, the purpose of the current study is to examine rates of self-reported exposure to traumatic events (particularly across different dimensions such as experiencing, witnessing, and across different event types) and PTSD symptoms (particularly across distinct domains of PTSD symptoms), and identify associations with demographic factors, among autistic adults.

Traumatic events among autistic adults

According to recent work, autistic youth experience higher rates of traumatic and adverse events than their nonautistic peers.^3–5 For the purposes of this study, “traumatic events” are defined as events that qualify criterion A of the PTSD diagnostic criteria according to the American Psychological Association, Diagnostic and Statistical Manual of Mental Health Disorders, Fifth Edition, Text Revision (DSM-5 TR⁶). Experiencing one of these events does not necessarily mean that someone will have a posttraumatic response (e.g., PTSD), nor are these defined events inclusive of all traumatic events. Traumatic events and PTSD among autistic individuals may be understood through a minority stress model of disability, which posits that autistic individuals experience unique physical and mental stressors related to their status as a marginalized identity (e.g., victimization, discrimination, stigma).^7,8

According to the DSM-5 TR,⁶ to meet criterion A of PTSD diagnostic criteria, one must directly experience, witness, learn about, or repeatedly experience exposure to details of events resulting in actual or threatened death, serious injury, or sexual violence.⁶ Importantly, this conceptualization of what constitutes a traumatic event is limited,⁹ and may exclude types of events that may be traumatic for autistic adults, such as social exclusion by peers and sensory trauma (i.e., differences in an individual's sensory processing and their environment, such as receiving haircuts or hearing fire alarms, consistent with Kerns et al.).¹⁰ Therefore, understanding the types of traumatic events that autistic adults may disproportionately experience can inform more personalized prevention and support strategies.

Existing research among autistic adults suggests that experiences of interpersonal trauma, such as physical and sexual assault and uncomfortable and/or unwanted sexual experiences, are particularly high.^1,11–13 Measures of exposures to traumatic events often require the determination of which event is perceived by the individual as the most distressing.¹⁴ This is important clinically, given that many PTSD-focused treatments may target the identified most distressing trauma or “index trauma” as the main focus for support.^15,16 Preliminary work by Golan et al.¹⁷ suggests that social traumatic events are rated as the most distressing for autistic adults, perhaps more so than for nonautistic adults (e.g., 45.6% of autistic adults rated a social traumatic event, such as bullying or shunning, as the most distressing relative to 25% of nonautistic adults¹⁷).

In the example of bullying or shaming, if there is not threat of death or injury, current diagnostic tools would exclude these experiences from being considered traumatic (as defined by criterion A) and therefore a trauma-related disorder may be missed.

Traumatic events occur at higher rates in marginalized populations, including those relating to gender identity (e.g., nonbinary, agender, and/or transgender people^11,18–20), race/ethnicity (e.g., Black/African American, Latino/e/a, or Native American individuals²¹), and socioeconomic status.²² In addition, autistic adults who identify with other intersecting marginalized identities (e.g., sexual and gender minorities, intellectual disability) may experience higher rates of trauma.^11,23–25 Other research has not found gender differences (e.g., differences between cisgender and gender-diverse adults) between autistic adults regarding rates of experiencing criterion A traumas, but only reported binary gender categories.^1,26 Thus, additional research on how gender and other demographic factors relate to traumatic events among autistic adults would greatly advance literature in this area.

PTSD symptoms among autistic adults

While some research has examined PTSD total symptom scores via self-report measures such as the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5²⁷) and found autistic samples to report higher overall PTSD scores than nonautistic samples,^12,26 less research has examined how PTSD symptom cluster scores may differ between groups. The DSM-5 TR identifies four domains of PTSD symptoms: intrusions (criterion B; e.g., recurrent, intrusive, involuntary memories of the traumatic event), avoidance (criterion C; e.g., avoiding external or internal reminders associated with the traumatic event), negative alterations in cognition and mood (criterion D; e.g., persistent negative beliefs about oneself, others, or the world), and alterations in arousal and reactivity (criterion E; e.g., hypervigilance).⁶

Understanding which types of symptom domains are highest among autistic adults may be important for selecting intervention approaches.²⁸ For example, more behaviorally focused PTSD therapies may most explicitly seek to support avoidance of real-world situations,²⁹ whereas more cognitively oriented PTSD therapies may most explicitly focus on negative changes in cognition and mood (e.g., guilt).¹⁶ Baseline symptoms of PTSD (i.e., symptoms that are present before beginning treatment) have been implicated in treatment response such that more symptoms with higher intensity predict lower response to treatment,³⁰ and these baseline symptoms of PTSD may be different for autistic adults relative to nonautistic adults. One study found that autistic adults report higher hyperarousal and negative cognition/mood symptoms,¹⁷ and other research has found that autistic adults report higher levels of intrusion/re-experiencing and hyperarousal symptoms compared with nonautistic adults.²⁶

Self-report measures of PTSD are often used to help detect a diagnosis. The PCL-5 was designed to reflect PTSD symptom criteria consistent with DSM-5.³¹ Across general populations, most research examining the underlying factors of the previous version of the PCL-5 supported a four-factor model consistent with PTSD symptom criteria.³² Much less is known about whether this four-factor structure of the PCL-5 is found among autistic adult populations, and whether it can be validly compared between autistic and nonautistic adults.

Regarding demographic disparities, previous research has highlighted that there may be important differences in the presentation of PTSD symptoms across various gender and racial/ethnic groups. Studies have demonstrated that women endorse higher distress across symptom clusters compared with men,³³ although fewer studies have included transgender and nonbinary individuals. Furthermore, some studies have found that Latino/e/a individuals are more likely to experience avoidance and numbing symptoms.³⁴ Symptoms of nightmares, flashbacks, and exaggerated startle response may be associated with PTSD presentations among Black Americans, although research of differences in PTSD symptom clusters among Black Americans describes mixed findings regarding which symptom clusters present in higher levels.^35,36

Goals of the current study

The current study aims to increase the knowledge of how autistic adults experience traumatic events. Specifically, we first aim to evaluate rates of traumatic events across different modes of exposure (i.e., directly experienced, witnessed, learned about), and identify rates of individual (item-level) traumatic events (e.g., car accidents, sexual assault). We also report descriptive information regarding worst-rated (e.g., most distressing) events. Second, we aim to evaluate how demographic factors (age, household income, gender, and race/ethnicity) relate to traumatic events. Third, we aim to identify rates of PTSD symptoms across domains, and we sought to confirm the PTSD symptom subscale structure of the PCL-5. In addition, we sought to identify how demographic factors relate to traumatic symptom domains to advance understanding of potential disparities in PTSD symptoms among autistic adults.

Methods

Participants

Participants in the current study were 276 autistic adults and a nationally representative sample of nonautistic adults (n = 361) from the United States. Demographic characteristics across groups are presented in Table 1. Autistic adults were significantly younger than nonautistic adults and reported significantly lower levels of household income. The group of autistic adults included a higher percentage of transgender and/or nonbinary adults (including those who selected any of the following: agender, not listed gender, transgender, or nonbinary), and a lower percentage of cisgender women than the group of nonautistic adults. Due to small numbers of transgender and/or nonbinary adults, particularly in the nonautistic group, we used a three-part variable for gender in substantive analyses (cisgender men, cisgender women, and transgender and/or nonbinary adults; consistent with Reuben et al.¹¹). The autistic group had a higher percentage of White/non-Hispanic adults and a lower percentage of Black/African American adults.

Table 1.

Demographic Characteristics of the Sample and Overall Traumatic Event and Symptom Descriptive Characteristics

	Autistic, M (SD)	Nonautistic, M (SD)	Group differences
			t(df)	p	Cohen's d
Age, years	29.00 (9.80)	45.69 (16.12)	t(606.66) = 16.15	<0.001	1.21
Household income, USD	34,933 (40,194)	56,753 (68,042)	t(588.13) = 4.99	<0.001	0.38
Autistic traits (AQ-Short score)	78.61 (11.28)	64.47 (10.72)	t(617) = 15.91	<0.001	1.29
Depression symptoms (PHQ-4)	2.92 (1.91)	1.55 (1.78)	t(570.53) = 9.33	<0.001	0.75
Anxiety symptoms (PHQ-4)	3.02 (1.87)	1.61 (1.92)	t(634) = 9.32	<0.001	0.75

	n, %		χ2	p
Gender			56.91, df = 2	<0.001
Cisgender woman	93, 33.7	180, 49.9
Cisgender man	128, 46.4	172, 47.6
Transgender or nonbinary	55, 19.9	9, 2.5
Race/ethnicity			15.38, df = 2	<0.001
White/non-Hispanic	205, 74.3	239, 66.2
Black/African American	14, 5.1	53, 14.7
Other/not listed	57, 20.7	69, 19.1

	Autistic, M (SD)	Nonautistic, M (SD)	t(df)	p	Cohen's d
Overall traumatic events (0–17)
Number happened to me	3.21 (2.67)	2.55 (2.44)	t(562.44) = −3.21	0.001	−0.26
Number witnessed	1.94 (2.50)	1.26 (2.00)	t(515.01) = −3.69	<0.001	−0.30
Number learned about	2.49 (3.97)	1.71 (3.31)	t(531.94) = −2.64	0.008	−0.22
Number part of job	0.28 (1.36)	0.11 (0.67)	t(377.37) = −1.82	0.07	−0.16
PCL symptom scores
Total score	39.14 (22.47)	24.22 (21.10)	t(626) = −8.53	<0.001	−0.69
Cluster B (re-experiencing)	9.97 (6.16)	6.56 (5.88)	t(626) = −7.06	<0.001	−0.57
Cluster C (avoidance)	4.55 (2.83)	3.37 (2.81)	t(626) = −5.18	<0.001	−0.42
Cluster D (Neg mood/cognition)	13.96 (8.63)	8.22 (8.05)	t(626) = −8.57	<0.001	−0.69
Cluster E (hyperarousal)	10.67 (6.76)	6.12 (6.26)	t(626) = −8.71	<0.001	−0.70

The transgender and/or nonbinary category consisted of those who selected transgender, nonbinary, agender, or not listed. The other/not listed race/ethnicity category consisted of those who selected Hispanic or Latino/a, bi- or multiracial, Asian or Asian American, Native Hawaiian or other Pacific Islander, American Indian or Native Alaskan, Middle Eastern, Southwest Asian, or North African, or not listed.

AQ-Short, Autism-Spectrum Quotient-Short; PCL, Posttraumatic Stress Disorder Checklist; PHQ-4, Patient Health Questionnaire-4; USD, U.S. dollars, rounded to the nearest dollar.

Given the low numbers of participants in most additional racial and ethnic groups, we used race/ethnicity as a three-part variable in substantive analyses (White/non-Hispanic, Black/African American, other/not listed). Autistic adults reported higher levels of co-occurring depression and anxiety. Lastly, the autistic group reported significantly higher levels of autistic traits on the Autism-Spectrum Quotient-Short Form (AQ-Short),³⁷ a self-report measure of autistic traits, with a large effect size (Table 1).

Participants indicated having received no diagnosis of autism (n = 361), having received a diagnosis by a professional (n = 214), or having received no diagnosis but self-identifying as autistic (n = 62). Participants who indicated having received a diagnosis were asked to provide the year that they received a diagnosis, the specific diagnosis they were given, and the type of provider who gave the diagnosis. Participants who received a diagnosis and who self-identified as autistic were considered together within one autistic group, as we recognize that autistic adults may encounter barriers to accessible diagnostic services or may be subject to underdiagnosis due to differences in presenting autistic traits.³⁸

There was no difference in autistic traits between autistic adults with a diagnosis (AQ-Short total score M = 78.64, SD = 11.28) and those who self-identified [AQ-Short total score M = 78.49, SD = 11.37; t(269) = 0.09, p = 0.93, Cohen's d = 0.01].

Procedures

We recruited participants from Prolific, an online survey platform that recruits more diverse participants and produces higher quality research than other survey platforms.^39,40 Inclusion criteria required participants to be at least 18 years old and to be able to read and respond to survey items in English. We used the Prolific feature for stratifying the sample to ensure national (United States) representation for recruiting the non-autistic participants. Participants completed a battery of Qualtrics measures that included several attention-check items to ensure validity of responses (e.g., being asked to give a specific response or select a specific answer choice). Only participants who passed all attention checks were included in data analyses, to be most conservative and to prioritize online data validity.

Participants (n = 39; n = 5.8% of original sample) who failed attention checks did not differ from participants who passed attention checks regarding the majority of study demographic variables, including autism group [χ² = 2.91, p (exact) = 0.24], age [t(674) = −0.36, p = 0.72], gender [χ² = 3.41, p (exact) = 0.19], nor race or ethnicity [χ² = 0.49, p (exact) = 0.81]. Those who failed attention checks reported a higher level of income than those who did not [t(653) = −2.25, p = 0.01]. After completion of the battery, we compensated participants and gave them debriefing materials (e.g., resources for mental health services).

This study received institutional review board approval. This was not a participatory study codesigned with autistic adults, which we recognize as a limitation of this study. All measures used in the current study demonstrated acceptable internal consistency; reliability values are provided in Supplementary Table S3.

Measures

Life Events Checklist for DSM-5

The Life Events Checklist for DSM-5 (LEC-5) is a 17-item self-report screening measure that assesses exposure to traumatic events based on DSM-5 conceptualizations of trauma.¹⁴ Participants indicate if an event happened to them, was witnessed, was learned about, occurred as part of their job, or if they were unsure. The LEC-5 screens for 16 traumatic events and includes a 17th item that asks whether the participant experienced “any other very stressful event or experience.” The participant indicates which of the 17 potential items they endorsed “bothers them the most” (the “index” event). We analyzed individual items, as well as sum scores for the number of events that were directly experienced (0–17), witnessed (0–17), learned about (0–17), and exposed to as part of their job (0–17).

Prior research among nonautistic adults has suggested that the LEC-5 demonstrates good test–retest reliability (r = 0.82) and moderate temporal stability (kappa = 0.61).⁴¹

Posttraumatic Stress Disorder Checklist for DSM-5

The PCL-5 is a 20-item self-report checklist that measures PTSD symptoms.²⁷ Items ask participants to rate how much they have been bothered by each symptom on a 5-point scale (i.e., Not at all, A little bit, Moderately, Quite a bit, Extremely). Items correspond to DSM-5 symptom clusters (i.e., items 1–5 correspond to intrusions, items 6–7 correspond to avoidance, items 8–14 correspond to negative mood or cognition, items 15–20 correspond to hyperarousal). Items are summed for a total score and for symptom cluster scores; higher scores indicate higher PTSD symptoms. The PCL-5 has demonstrated strong internal consistency (Cronbach's alpha ranging from 0.92 to 0.94)^12,26 among autistic adults in existing research, with comparable psychometrics among nonautistic samples (Cronbach's α = 0.94).³¹

Autism-Spectrum Quotient-Short

The AQ-Short is a 28-item abridged self-report measure that identifies autistic traits.³⁷ Participants respond to each item on a 4-point Likert scale (i.e., 1 = Definitely Agree, 2 = Slightly Agree, 3 = Slightly Disagree, 4 = Definitely Disagree), with reversed scoring for some items. Item scores are then summed for a total AQ-Short score that can range from 28 to 112, with higher scores indicative of higher levels of autistic traits. The AQ-Short has demonstrated acceptable internal consistency (Cronbach's alpha's ranging from 0.77 to 0.86).³⁷

Patient Health Questionnaire-4

The Patient Health Questionnaire-4 (PHQ-4) is a 4-item self-report measure used to identify core symptoms of depression and anxiety.⁴² For each item, participants respond on a 4-point Likert scale (i.e., 0 = Not at all, 1 = Several days, 2 = More than half the days, 3 = Nearly every day) and indicate how much each item has been a problem over the last 2 weeks. Scores are summed and can range from 0 to 12, with higher scores indicating higher levels of depression and anxiety. The PHQ-4 has been shown to be reliable in prior research (Cronbach's α >0.80).⁴²

Analytic strategy

First, all composite variables were inspected for skewness. All internal consistency values for measures are presented in Table 1. We then present descriptive information, including group differences in the overall traumatic event (LEC-5) and symptom (PCL-5) domains. As this was our primary aim, the sample size was designed to detect at least medium effect size for these group analyses, given that we anticipated autistic adults to experience moderately more traumatic events and symptoms. This is consistent with recent research that has shown medium effects for number of trauma exposures (Cohen's d = 0.71, medium effect) and trauma symptoms (Cohen's d = 1.3, large effect).¹² Post hoc power analyses confirmed sufficient power (∼0.80 or higher) for all group differences based on observed effect sizes.

We then examined whether differences in traumatic event and symptom domains between autistic and nonautistic adults are maintained when accounting for differences in demographic characteristics and co-occurring anxiety and depression across groups. Then, the first half of our analytic strategy further examines traumatic events as reported on the LEC-5 (experienced, witnessed, learned about). We conducted chi-square analyses to examine whether rates of each type of traumatic event differed among autistic and nonautistic adults, and we present descriptive information regarding most distressing traumatic events experienced across groups. Lastly, we conducted exploratory analysis to examine how demographic factors were associated with traumatic events, using MANOVA for categorical variables (gender, race/ethnicity) and correlational analyses for continuous variables (age, income). We conducted separate analyses among autistic and nonautistic adults to identify whether patterns of associations between demographic factors and traumatic event experiences differed across groups.

The second half of our analytic strategy further examines posttraumatic symptoms via the PCL-5. First, we examined whether the DSM-5 four-subscale-factor structure adequately represented the data equivalently across autistic and nonautistic adults via analysis of factorial invariance, with missing data handled using full information maximum likelihood. We evaluated models using the root mean square error of approximation (RMSEA values <0.08 indicate ideal fit), Bentler's comparative fit index (CFI values >0.90), and the standardized root mean scale residual (SRMR <0.08).⁴³ We used Little's (2013) stepwise procedure to ascertain invariance of the four-factor model across autistic and nonautistic adults, including configural (whether overall factor structure fits well across groups), metric (equivalent factor loadings), and scalar (equivalent item intercepts) invariance.

Invariance was supported if the change in model fit at each step was negligible (e.g., SRMR change less than 0.030 for metric and 0.010 for scalar; change in CFI and RMSEA does not exceed 0.010–0.015).⁴⁴ Lastly, we conducted exploratory analyses to examine how demographic factors were associated with the PTSD subscale and total scores across autistic and nonautistic adults (using MANOVA for categorical variables and correlation analyses for continuous variables). We conducted analyses using Statistical Packaging for the Social Sciences (SPSS) version 28.0, with factor analyses conducted via Mplus version 8.5.

Results

Skewness and kurtosis of all composite variables were within acceptable ranges, with the exception of the total number of traumatic events experienced as part of one's job and income. Skewness for income was corrected with a square root transformation; the transformed variable was used in all further analyses. Descriptive statistics regarding group differences in rates of overall traumatic events and symptoms are presented in Table 1. Autistic adults reported significantly more traumatic events that directly happened to them, and that they witnessed and learned about, with small effect sizes. Autistic and nonautistic adults did not significantly differ on the number of traumatic events experienced as part of one's job via an independent-sample Mann–Whitney U-test (p = 0.326). Given this and high skew, the number of traumatic events experienced as part of one's job was not included as a variable in further analyses.

Autistic adults also reported significantly higher scores on all PTSD symptom domains on the PCL-5, with the largest effect size for hyperarousal symptoms (Table 1). Item-level responses on the PCL-5 across groups are presented in Supplementary Table S1.

We considered possible differences in traumatic events and symptoms by comparing group differences on (1) formally diagnosed with nonautistic adults and (2) self-identified with nonautistic adults. When comparing the formally diagnosed autistic adults with nonautistic adults, all of the t-tests reported above remained significant, with the exception of the number of learned about events [t(383.30) = 1.83, p = 0.067]. When comparing the self-identified autistic adults with nonautistic adults, all of the t-tests reported above remained significant. Thus, for all the subsequent analyses, the autistic group consists of both formally diagnosed and self-identified individuals.

We conducted follow-up MANOVAs to explore group differences when accounting for differences in age, gender, race/ethnicity, and income, as well as co-occurring internalizing symptoms of depression and anxiety. The significant multivariate overall main effect of group (autistic or nonautistic adults) was maintained for the traumatic event domains [number happened, witnessed, learned about, F(3, 605) = 4.25, p = 0.005] and the traumatic event symptom domains [F(4, 597) = 2.55, p = 0.038]. For events, tests of between-subjects effects were significant for number of directly experienced and witnessed events and were nonsignificant for number of learned about events (p = 0.055). For symptoms, tests of between-subjects effects were significant for the total PCL score and all symptom domains with the exception of cluster C (avoidance symptoms, p = 0.309).

Thus, on average, autistic adults experienced and witnessed more traumatic events and endorsed more symptoms across all domains except for avoidance when accounting for group differences in demographic factors and co-occurring anxiety and depression symptoms.

Item-level traumatic events

We report frequencies and chi-square group differences for each type of individual traumatic event in Table 2. For directly experienced events, autistic adults reported significantly higher rates of physical assault, sexual assault, other unwanted or uncomfortable sexual experiences, and severe human suffering. Autistic adults reported significantly lower rates of transportation accidents. Autistic adults reported significantly higher rates of witnessing toxic substance exposure, physical assault, assault with a weapon, sexual assault, other unwanted/uncomfortable sexual experiences, captivity, and sudden violent death. Autistic adults also reported significantly higher rates of learning about several traumatic events happen (natural disaster, fire/explosion, transportation accident, physical assault, combat/war, and captivity), and traumatic events they were exposed to as part of a job (sexual assault, unwanted/uncomfortable sexual experience, combat/war, captivity, severe human suffering).

Table 2.

Item-Level Traumatic Event Rates Between Groups

	Happened to me			Witnessed			Learned about			Part of job
	%		χ2	%		χ2	%		χ2	%		χ2
	Aut	N-A		Aut	N-A		Aut	N-A		Aut	N-A
Natural disaster	21.4	26.6	2.311	15.2	13.0	0.629	18.5	11.1	6.991**	0.4	0.3	0.036
Fire/explosion	10.1	7.5	1.409	14.1	14.7	0.038	15.6	9.7	5.040*	0.4	0.6	0.123
Transportation accident	35.1	44.9	6.138*	20.3	17.2	1.006	14.5	7.8	7.444**	1.1	1.7	0.371
Other accident	13.8	11.6	0.648	11.6	8.6	1.587	13.4	8.9	3.340	1.8	0.8	1.213
Toxic substance	5.1	3.3	1.221	4.0	0.8	7.241*	10.5	7.2	2.166	0.4	1.7	2.431
Physical assault	48.6	31.3	19.602***	23.9	12.7	13.469***	14.1	8.9	4.380*	0.7	0.6	0.073
Weapon assault	11.6	10.5	0.182	10.1	5.3	5.455*	14.1	9.1	3.884	1.8	0.8	1.213
Sexual assault	30.4	19.9	9.308**	5.1	1.9	4.817*	19.9	14.1	3.793	3.3	0.3	9.013**
Unwanted sexual experience	48.9	33.5	15.422***	8.0	1.9	13.097***	14.5	9.4	3.923	2.2	0.0	7.922**
Combat/war	0.7	1.9	1.656	1.4	1.4	0.005	12.3	6.9	5.414*	2.9	0.0	10.597**
Captivity	4.0	3.0	0.413	2.5	0.6	4.412*	10.9	6.4	4.149*	2.2	0.0	7.922**
Illness/injury	15.6	16.9	0.199	15.9	12.2	1.851	14.5	9.4	3.923	1.4	1.1	0.147
Severe human suffering	14.1	4.4	18.649***	16.7	11.4	3.739	17.8	17.2	0.036	2.5	0.3	6.438*
Sudden violent death	3.6	3.0	0.163	10.9	4.7	8.686**	25.7	20.2	2.707	2.2	0.8	2.025
Sudden accidental death	3.6	3.9	0.028	10.1	6.9	2.126	17.8	15.0	0.902	1.1	0.8	0.110
Serious injury, harm, or death caused to other	2.9	1.9	0.626	5.4	3.6	1.251	4.0	3.3	0.197	0.7	0.6	0.073
Other very stressful event/experience	51.8	31.0	28.189***	18.5	9.1	11.911***	11.2	6.6	4.166*	2.5	1.1	1.880

Significant differences are bolded for the reader.

^* p < 0.05, ^**p < 0.01, ^***p < 0.001.

Aut, autistic; N-A, nonautistic.

In addition, autistic adults were also significantly more likely to endorse experiencing, witnessing, and learning about an “other” stressful event or experience not captured by the other items on the LEC-5.

Worst traumatic event

Among autistic adults, 20.7% reported sexual assault as their “worst” (most distressing) event, followed by any other very stressful event or experience (experiences not captured by the LEC-5, 15.9%), and physical assault (11.1%). Among nonautistic adults, 12.4% reported sexual assault as their worst event, followed by any other very stressful event or experience (12.1%) and life-threatening illness or injury (10.7%). See Supplementary Table S2 for additional descriptive information regarding worst-rated events.

Traumatic events and associations with demographic factors across groups

Exploratory associations between demographic factors with traumatic events (number experienced, number witnessed, and number learned about) across groups are presented in Table 3. Throughout this section, when an overall MANOVA multivariate effect was significant, only significant between-subjects effects and the subsequent significant Bonferroni-corrected comparisons are reported. There was a significant overall MANOVA multivariate effect of gender for autistic [F(6, 542) = 2.918, p = 0.008] and nonautistic [F(6, 712) = 6.78, p < 0.001] adults. For both autistic and nonautistic adults, tests of between-subjects effects were significant for the number of directly experienced events (Table 3). Post hoc Bonferroni-corrected comparisons showed that transgender and/or nonbinary autistic individuals reported experiencing significantly more traumatic events than autistic cisgender men. Among nonautistic adults, cisgender women reported significantly more experienced events than cisgender men.

Table 3.

Demographic Associations with Traumatic Event Dimensions Across Groups

	Happened		Witnessed		Learned
	F	p	F	p	F	p
MANOVA between-subjects effects
Gender—autistic adults	7.30	<0.001	1.33	0.266	1.28	0.281
Post hoc findings	TNB > M
Gender—nonautistic adults	11.67	<0.001	5.61	0.004	3.34	0.037
Post hoc findings	W > M		TNB > W TNB > M		TNB > W
Race/ethnicity—autistic adults	—	—	—	—	—	—
Race/ethnicity—nonautistic adults	—	—	—	—	—	—

	r	p	r	p	r	p
Correlations
Age—autistic adults	0.28	<0.001	0.01	0.827	0.08	0.208
Age—nonautistic adults	0.13	0.015	−0.04	0.037	0.04	0.472
Income—autistic adults	−0.09	0.160	0.09	0.154	0.09	0.164
Income—nonautistic adults	−0.05	0.324	0.03	0.578	0.00	0.970

Bolded values indicate significance. —, nonsignificant multivariate test for MANOVA, precluding interpretation of between-subjects effects.

M, men; TNB, transgender and/or nonbinary; W, women.

Among nonautistic adults, tests of between-subjects effects were also significant for the number of witnessed and learned about events (Table 3). Post hoc comparisons showed that transgender and/or nonbinary adults had more witnessed events compared with cisgender women and cisgender men, and more learned about events than cisgender women. There was neither a significant overall MANOVA multivariate effect of race/ethnicity for nonautistic adults [F(6, 712) = 1.35, p = 0.232], nor for autistic adults [F(6, 542) = 1.039, p = 0.399]. Correlations for age and income are also shown in Table 3. Age significantly correlated with more experienced events among autistic and nonautistic adults.

PCL-5 factor structure of PTSD symptoms

To examine whether the DSM-5-based PCL-5 subscale factor structure fits the data well across autistic and nonautistic adults, we conducted a confirmatory factor analysis with configural, metric, and scalar invariance assessed across groups. A four-factor model specifying each of the subscales aligning with DSM-5 clusters demonstrated acceptable fit separately within the autistic (RMSEA = 0.075; CFI = 0.921; SRMR = 0.042) and nonautistic groups (RMSEA = 0.075; CFI = 0.923; SRMR = 0.042). Then, the four-factor solution was fit to equivalent configuration across autistic and nonautistic adults; the baseline configural model had an acceptable model fit (RMSEA = 0.075, CFI = 0.922, SRMR = 0.042). Setting each loading to be equivalent across autistic and nonautistic adults did not result in significant change to the fit indices (RMSEA = 0.075, change = 0.000; CFI = 0.919, change = −0.003; SRMR = 0.049, change = +0.007), supporting metric invariance.

Imposing equality constraints on each observed intercept also did not result in significant decrements in model fit (RMSEA = 0.074, change = −0.001; CFI = 0.917, change = −0.002; SRMR = 0.049, change = 0.000), supporting scalar invariance. Thus, we used the four subscales in the analyses moving forward to represent the four DSM-5 symptom clusters.

Demographic associations with PCL-5 symptom domains across groups

Exploratory associations between demographic factors with traumatic symptom domains across groups are presented in Table 4. As above, only significant between-subjects effects and the subsequent significant Bonferroni-corrected comparisons are reported. There was a significant overall MANOVA multivariate effect of gender for autistic [F(8, 530) = 3.31, p = 0.001] and nonautistic [F(8, 700) = 3.96, p < 0.001] adults. For both autistic and nonautistic adults, tests of between-subjects effects were significant for all trauma symptom domains (Table 4). Across groups, transgender and/or nonbinary adults had higher levels of all symptoms than cisgender men. In the nonautistic group, transgender and/or nonbinary adults also had higher levels of all symptoms than cisgender women (although these comparisons were not significant for the autistic group).

Table 4.

Demographic Associations with Traumatic Symptom Dimensions Across Groups

	PCL B Re-Exp		PCL C Avoidance		PCL D Neg Cog/mood		PCL E Hyperarousal		PCL total Overall PTSD
	F	p	F	p	F	p	F	p	F	p
MANOVA between-subjects effects
Gender—autistic adults	8.90	<0.001	9.12	<0.001	8.08	<0.001	9.29	<0.001	10.28	<0.001
Post hoc findings	TNB > M		TNB > M W > M		TNB > M		TNB > M W > M		TNB > M W > M
Gender—nonautistic adults	13.26	<0.001	5.70	0.004	8.79	<0.001	7.40	<0.001	10.56	<0.001
Post hoc findings	TNB > M TNB > W W > M		W > M		TNB > M TNB > W W > M		TNB > M TNB > W		TNB > M TNB > W W > M
Race/ethnicity—autistic adults	—	—	—	—	—	—	—	—	—	—
Race/ethnicity—nonautistic adults	—	—	—	—	—	—	—	—	—	—

	r	p	r	p	r	p	r	p	r	p
Correlations
Age—autistic adults	−0.01	0.939	−0.06	0.341	−0.06	0.317	−0.05	0.415	−0.05	0.441
Age—nonautistic adults	−0.17	0.001	−0.14	0.011	−0.26	<0.001	−0.25	<0.001	−0.23	<0.001
Income—autistic adults	−0.11	0.087	−0.08	0.209	−0.16	0.009	−0.12	0.043	−0.14	0.025
Income—nonautistic adults	−0.09	0.087	−0.09	0.086	−0.12	0.025	−0.10	0.059	−0.11	0.039

Bolded values indicate significance. —, nonsignificant multivariate test for MANOVA, precluding interpretation of between-subjects effects.

PTSD, posttraumatic stress disorder.

Cisgender women had higher scores than cisgender men on three out of five domains in the autistic group (avoidance, hyperarousal, and overall PTSD symptoms), and on all domains in the nonautistic group.

There were nonsignificant overall MANOVA multivariate effects of race/ethnicity for autistic adults [F(8, 530) = 1.89, p = 0.06] and nonautistic adults [F(8, 700) = 1.13, p = 0.34; Table 4]. Correlations for age and income are also shown in Table 4. Age was unrelated to PTSD symptoms among autistic adults but was negatively and significantly related to PTSD symptoms among nonautistic adults. Higher income was associated with lower levels of total PTSD symptoms and negative cognition/mood symptoms among autistic adults, and with lower levels of total PTSD symptoms among nonautistic adults.

Discussion

The current study sought to examine rates of self-reported traumatic events and PTSD symptoms, and identify associations with demographic factors, among autistic adults. The results importantly expand existing literature by indicating that autistic adults report experiencing more traumatic events (including those that are directly experienced, witnessed, and learned about) with differential item-level findings. Results also showed that the four-factor structure of PTSD symptoms was invariant and thus meaningfully comparable across autistic and nonautistic adults using the PCL-5. Autistic adults reported significantly higher levels of all PTSD symptom domains, with the largest effect size for hyperarousal and negative mood/cognition symptoms. Results also revealed exploratory associations for traumatic events and symptoms with demographic factors.

These findings are theoretically supported by the minority stress model of disability, as higher rates of traumatic events and PTSD symptoms may be a reflection of the impact of higher levels of stressors that autistic adults disproportionately experience in society.^7,8

Traumatic event experiences

Our results were consistent with existing literature showing that autistic adults experience higher rates of traumatic events overall, including on measures such as the LEC-5.^12,26 Our findings also extend prior work by showing that in our sample, autistic adults are also more frequently exposed to potential trauma in other ways than directly experiencing trauma (e.g., by witnessing traumatic events and learning about traumatic events). When accounting for demographic factors and co-occurring depression and anxiety symptoms across groups, these findings were maintained, with the exception of learned about events.

At the item-level, our finding that the most common worst-rated trauma event among autistic adults was sexual assault (∼20%) aligns with previous research highlighting that autistic adults disproportionately experience interpersonal and social trauma.^1,12,13,17 Although autistic adults endorsed significantly lower rates of transportation accidents than nonautistic adults, 35.1% of autistic adults still endorsed traumatic transportation accidents, emphasizing the importance of also developing supports related to this type of trauma. These may include improving or developing programs to support professionals such as social workers, victim advocates, and others who interact with autistic adults following exposure to a traumatic event. Autistic adults also endorsed higher rates of individual (item-level) traumatic experiences as part of their job. Although the total number of events experienced as part of one's job did not differ across groups, we examined item-level findings to inform future research in this area.

Recent research has identified specific employment-related challenges that autistic adults report experiencing, which may include sensory sensitivities and social stressors (e.g., meeting social expectations, peer victimization) that can be traumatic for autistic employees,⁴⁵ although more work should clarify how these types of stressors may be associated with (or distinct from) posttraumatic stress-related sequelae.

Consistent with prior research, transgender and/or nonbinary autistic adults experienced more traumatic events than cisgender autistic men.¹¹ Moreover, increasing age related to directly experiencing more traumatic events among autistic adults. This underscores the importance of supporting older autistic adults, who are often excluded from autism research.⁴⁶ This finding may also reflect more cumulative traumatic events experienced by autistic people, although additional research should clarify this. Experiencing higher levels of adverse events has been associated with an accumulation of poor physical and behavioral health outcomes among autistic individuals.⁴ Among nonautistic adults, experiencing cumulative trauma has been associated with a variety of complex long-term outcomes with the potential to include declines in life satisfaction and health across the life span.⁴⁷

PTSD symptom factor structure and associations across groups

Measurement invariance analyses from the current study suggest that significant group differences in the PTSD symptom subscales are statistically meaningful and not a measurement artifact, as scalar invariance was established in these data. Future research should expand this work to further confirm this finding and examine the use of other PTSD symptom measures, such as the Clinician-Administered PTSD Scale for DSM-5,⁴⁸ for autistic adults.

Autistic adults reported higher rates of overall trauma symptoms across symptom clusters compared with nonautistic adults. This is consistent with prior research that has highlighted higher PTSD total severity scores among autistic populations,^1,2,26 and extends prior findings^12,26 by showing statistically significant group differences on all PTSD symptom domains, including avoidance symptoms (i.e., avoiding thoughts and feelings related to the trauma, avoiding external cues related to the trauma). In addition to re-experiencing/intrusions, hyperarousal, and negative mood/cognition symptoms,^17,26 this study is among the first to show that autistic adults also report higher levels of avoidance symptoms. However, when accounting for demographic factors and co-occurring depression and anxiety symptoms across groups, group differences were maintained for all symptom clusters except avoidance symptoms, which may suggest that elevations in PTSD symptoms (except avoidance) are not fully overlapping with mental health.

It is essential that future work considers a range of mental health outcomes in addition to PTSD symptoms to better understand the mental health impacts of traumatic events. We observed the largest effect size for negative mood/cognition and hyperarousal symptoms, suggesting that autistic adults may experience heightened symptom severity and distress in these domains.

Patterns of associations between PTSD symptoms and gender were similar in both groups. Among autistic and nonautistic adults, transgender and nonbinary individuals, as well as cisgender women, reported higher levels of most domains of PTSD symptoms than cisgender men, similar to prior work.^11,20 Although not directly investigated in the current study, autistic women and gender minorities may disproportionately experience trauma symptoms due to the lack of overall support and mental health support services, as well as additional stigma and minority stress.⁷ These individuals may have received an autism diagnosis later in life or not at all, potentially leading to missed opportunities for accessible supports compared with their earlier diagnosed peers. There has been an increase in autism diagnoses among adults over the last several years,⁴⁹ with a higher rate of women and nonbinary individuals composing this group of adults.^50–52

Relatedly, social and community support has been identified as a factor that may promote resilience and positive outcomes (e.g., physical and psychological health), even after experiencing stressful events, across the life span.⁵³ Among autistic adults, those reporting lower levels of social support have been shown to experience lower quality of life and greater impacts of stressful events on well-being.^54,55 Relatedly, high levels of community support and community connectedness may improve well-being⁵⁶ and protect autistic individuals from stigma and social stress,⁵⁷ suggesting that social support may be an important target in future work examining PTSD symptoms among autistic adults.

Regarding additional demographic factors and PTSD symptoms, lower income related to higher levels of most PTSD symptoms similarly among autistic and nonautistic adults, emphasizing the urgent need to disseminate low-cost supports relating to PTSD symptoms. Relatedly, the autistic group in the current study had a significantly lower average income than the nonautistic group, which holds important clinical support implications when coupled with the higher rates of traumatic events and symptoms experienced. Specifically, prior research has identified that community providers may be less likely to treat trauma-related symptoms among autistic youth from lower socioeconomic backgrounds,⁵⁸ highlighting a need for trauma-related supports for autistic people across the life span and from a range of socioeconomic backgrounds.

Training health care professionals to recognize trauma among autistic people of all backgrounds will be critical in increasing services, as many providers report receiving little or no training in supporting autistic adults and may already have more difficulty recognizing PTSD among autistic people.^25,59,60 Increasing community support (e.g., activism)⁶¹ for autistic people may also improve the accessibility of general support for autistic adults. Higher age was related to lower PTSD symptoms among nonautistic adults (but was unrelated to PTSD symptoms among autistic adults).

Limitations and future directions

The findings of the current study should be interpreted within the context of its limitations. First, we only collected information regarding DSM-5 criterion A events as reflected by the LEC-5 as opposed to assessing for and analyzing a wider range of traumatic events commonly endorsed among autistic individuals, such as bullying or sensory traumas.^1,10 Rumball et al. highlighted that it is essential to assess for a broader range of potentially traumatic events,¹ given that the traditional range of events consistent with the DSM-5 excludes many traumatic events experienced by autistic adults (e.g., peer victimization). Future studies should aim to investigate a broad range of traumatic events more comprehensively—including DSM-5 and non-DSM-5 traumas—among autistic individuals in relation to PTSD symptoms and PTSD treatment. Better understanding exposure to traditional and nontraditional traumatic events may better inform tailored prevention and intervention strategies and promote autistic flourishing.

In addition, it is essential to consider a wider range of mental health outcomes alongside traumatic events and PTSD symptoms in future research, to better understand the potential mental health impacts of traumatic events. In addition, it may be important to consider sensory sensitivities along with mental health outcomes, especially given that sensory trauma has been identified in qualitative work with autistic people.¹⁰

Relatedly, we did not clarify for participants definitions for the modes of experiencing traumatic events on the LEC-5 (i.e., directly experiencing, witnessing, learning about, experiencing as part of one's job) nor did we provide examples that distinguish these modes from one another. As such, future work should seek to determine any differences in item interpretation between autistic and nonautistic adults on this and related measures. Cognitive interviewing approaches have been used successfully with autistic adults to guide researchers toward developing increasingly accessible measures,⁶² and such approaches may be useful to use with the LEC-5 and other common trauma event screening tools. Similarly, it may be important for future work to consider the validity of alternative forms of trauma-related data collection (e.g., informant-report versions of the LEC-5 or other screening tools) to best support autistic adults who may benefit from adaptations to self-reported measures.

Although a large portion of our sample identified as non-White and/or as a gender minority, the majority of our sample was White (69.7%), which may have contributed to the lack of exploratory associations between race/ethnicity and rates of PTSD symptoms across groups of autistic and nonautistic adults. Future studies should attempt to collect data from a more diverse sample, with higher power to examine these associations across different groups. In addition, it is known that individuals with minoritized identities may experience higher rates of mental health concerns,⁸ and those with intersecting minority identities may experience a multiplicative effect of mental health difficulties.⁶³

Therefore, it is important for future studies to apply an intersectional framework to research on autism and trauma.⁶⁴ Furthermore, mixed-method, qualitative, and codesigned participatory research will be essential for amplifying autistic perspectives on this critical research area and ensuring that future work aligns with the research priorities of autistic people.^65,66

Future work focusing on improving intervention and support strategies should remain consistent with the priorities of autistic people. These may include training first responders (e.g., police) and mental health care professionals in being knowledgeable about how to support autistic people, as this has been identified as a need.^25,59–61 Focusing on increasing support at the community level may foster autistic-led supports and increase accessibility of supports for autistic people,^57,61 and promoting self-advocacy will be important for increasing support at the individual and community level.⁶⁵

Authorship Confirmation Statement

Conceptualization: T.A. and C.G.M.

Formal analysis: T.A. and C.G.M.

Investigation: C.G.M.

Writing—original draft: T.A., S.G.B., T.A.-R., K.E.B., A.U.T., and C.G.M.

Writing—review and editing: S.G.B., T.A.-R., K.E.B., A.U.T., A.W., D.C.R., and C.G.M.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

Coauthor Kaitlyn E. Breitenfeldt was supported by an Institutional Development Award (IdeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number 2P20GM103432. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.