Abstract
There is a lack of nationally representative studies examining the co-occurrence of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) in children. This study examines comorbid mental, behavioral, and developmental disorders (MBDDs) and associated treatment modalities for children with co-occurring ASD and ADHD. Cross-sectional analyses were conducted using data from the pooled 2016-2018 National Survey of Children’s Health (sample n = 102,341). Nationally representative prevalences were estimated for sociodemographic variables, comorbidities, psychotropic medication, and behavioral treatment. We assessed multivariable associations between co-occurring ASD+ADHD and MBDDs, use of psychotropic medication, and receipt of behavioral treatment after adjustment for sociodemographic confounders. Compared to children with ASD without co-occurring ADHD, children with ASD+ADHD had higher prevalence of most MBDDs, including anxiety (AOR 4.03 [95% CI 2.77, 4.87]), depression (AOR 3.08 [95% CI 1.77, 5.36]), behavior or conduct problems (AOR 4.06 [95% CI 2.72, 6.06]), and other mental health conditions. Similarly, compared to children with ADHD without ASD, children with ASD+ADHD had higher odds of anxiety (AOR 3.49 [95% CI 2.65, 4.61]), depression (AOR 1.67 [95% CI 1.21, 2.29]), behavior or conduct problems (AOR 2.31 [95% CI 1.68, 3.17]), and other mental health conditions. Children with ASD+ADHD were significantly more likely to take psychotropic medication than children with ASD without ADHD. Among children with ASD+ADHD, males had higher odds of receiving behavioral treatment, whereas older children and adolescents were more likely to take psychotropic medication. A multidisciplinary approach is necessary to support the complex needs of these children.
Keywords: Autism spectrum disorder, Attention-deficit/hyperactivity disorder, Co-occurring ASD and ADHD, Mental and behavioral disorders, National Survey of Children’s Health
Lay Summary
This study examines mental, behavioral, and developmental disorders (MBDDs) and associated treatment for children with co-occurring autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Compared with children with ASD or ADHD alone, children with ASD+ADHD are more likely to have MBDDs and use psychotropic medication. Our research presents insights into the clinical characteristics of children with co-occurring ASD+ADHD. Given the rising number of children with ADHD and ASD, findings have important implications for both public health policy and clinical care.
Introduction
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by persistent impairments in social communication and interaction and the presence of restricted, repetitive patterns of behaviors, interests, or activities (American Psychiatric Association, 2013). Prevalence of ASD in the United States among children aged 8 years has increased from 0.4% in 1996 to 2.3% in 2018, based on reports from the Centers for Disease Control and Prevention’s Autism and Developmental Disabilities Monitoring (ADDM) Network (Maenner et al., 2021; Van Naarden Braun et al., 2015). Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder among children (Perou et al., 2013) and has also increased in the past two decades from 6.1% in 1997 to 10.2% in 2016 (Danielson et al., 2018; Xu et al., 2018). ADHD symptoms include pervasive inattentiveness, impulsivity, or hyperactivity that lead to impaired functioning (American Psychiatric Association, 2013).
According to a recent study, 1.2% of U.S. children have co-occurring ASD+ADHD (Casseus, 2022). A high prevalence of clinical comorbidity is associated with co-occurrence of the two conditions, and phenotypical, clinical, genetic, neuropsychological, and behavioral characteristics substantially overlap between the two disorders (Joshi et al., 2017; Rommelse et al., 2011; Ronald et al., 2008; Sokolova et al., 2017; Taurines et al., 2012). Though evidence of this overlap had been documented for many years, the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) lessened barriers for clinicians to make dual diagnoses of ASD and ADHD (American Psychiatric Association, 2013).
Research analyzing the prevalence of ASD among children diagnosed with ADHD or the prevalence of ADHD among children diagnosed with ASD often focuses on symptomatology. While estimates vary widely based on assessments used and populations examined, between 14% to 62% of children diagnosed with ASD also have ADHD (Gordon-Lipkin et al., 2018; Rau et al., 2020; Ronald et al., 2008; Sikora et al., 2012; Supekar et al., 2017). The percentage of children diagnosed with ADHD who meet criteria for ASD is lower, ranging from 13% to 22% (Ronald et al., 2008; Zablotsky et al., 2017).
In addition to examining prevalence of ADHD among children with ASD or ASD in children with ADHD, several studies have found children with co-occurring ASD and ADHD (ASD+ADHD) present with severe functional impairments and other deficits. Higher levels of psychopathology, including internalizing and externalizing problems, have also been reported among young children with ASD+ADHD compared with children with ASD alone (Hong et al., 2021). Children with ASD+ADHD have greater prevalence of anxiety, mood disorders, tantrums, oppositional and avoidant behaviors, conduct problems, and developmental disorders (Gadow et al., 2009; Gordon-Lipkin et al., 2018; Jang et al., 2013; Mulligan et al., 2009; Zablotsky et al., 2017). Increased neurodevelopmental disorders, greater level of ASD severity, repetitive behaviors, and language and social deficits were also observed in children with ASD+ADHD (Gadow et al., 2009; Gordon-Lipkin et al., 2018; Mulligan et al., 2009). Further, compared with children with ASD without co-occurring ADHD, children with ASD+ADHD have been shown to exhibit lower cognitive and adaptive functioning, more severe social impairment, and have a poorer health-related quality of life (Rao & Landa, 2013; Sikora et al., 2012).
While the body of literature on co-occurring ASD+ADHD continues to grow, many questions remain unanswered. Although the extant literature provides information regarding the complex nature of co-occurring ASD+ADHD, the research has been limited in two important ways. First, studies have been conducted almost exclusively within small clinical or community samples, or samples from autism registries, resulting in limited generalizability. Second, as previously noted, the research has primarily focused on children who were clinically diagnosed with ASD presenting with ADHD symptoms, or children with ADHD presenting with ASD symptoms, rather than children with clinical diagnoses of comorbid ASD+ADHD. Research examining children diagnosed with ASD+ADHD may reveal differences in this distinct population, which, in turn, may help guide effective interventions (Gordon-Lipkin et al., 2018; Young et al., 2020). There has been a lack of nationally representative studies examining the co-occurrence of ASD and ADHD in children, and these studies that have not compared the clinical characteristics of children with ASD+ADHD with those of children with ADHD or ASD alone (Casseus, 2022; Zablotsky et al., 2017).
To address this gap in the literature, the current study analyzed data from the National Survey of Children’s Health (NSCH), a nationally representative survey of children aged 0 to 17 years. The objectives of our study were twofold: (a) to assess the prevalence of comorbid mental, behavioral, and developmental disorders (MBDDs) among U.S. children diagnosed with ASD+ADHD, children diagnosed with ASD without co-occurring ADHD, and children diagnosed with ADHD without co-occurring ASD; and (b) to examine factors associated with receipt of behavioral treatment and psychotropic medication by children with ASD+ADHD.
Methods
Data source
Data were analyzed from the public-use data files of the 2016–2018 NSCH, a cross-sectional, nationally representative, self-administered survey of U.S. children aged 0-17 years. The NSCH is funded and directed by the U.S. Department of Health and Human Services’ Health Resources and Services Administration’s Maternal and Child Health Bureau and conducted by the U.S. Census Bureau (Data Resource Center for Child and Adolescent Health, 2021a). It is designed to provide national and state-level prevalence estimates of the physical and emotional health and well-being of children under the age of 18 years, their families and their communities, as well as information about the prevalence and impact of special health care needs among children. The NSCH used address-based sampling of households in the 50 states and the District of Columbia. A screener questionnaire identified households with children. A topical questionnaire collected detailed information about one child selected at random from the household with oversampling for young children and children with special health care needs (Data Resource Center for Child and Adolescent Health, 2021b).
Data were collected using a paper or web-based survey instrument. Respondents were parents or other caregivers (hereafter referred to as parents) with knowledge of the child’s health and health care. Surveys were available in both English and Spanish and were completed by 102,341 respondents for the three sampled years. The overall response rates, including from households without children, were 40.7% (2016), 37.4% (2017), and 43.1% (2018). All analyses were weighted to account for the complex sample design, unequal probability of selection and differential nonresponse by various sociodemographic factors, and to represent all noninstitutionalized U.S. children. Prior to public release, all data went through a disclosure review process and were approved by the Census Disclosure Review Board.
Study description
To ascertain diagnosis of ASD, parents were asked, “Has a doctor or other health care provider ever told you that this child has autism or autism spectrum disorder (ASD), including diagnoses of Asperger’s Disorder or pervasive developmental disorder (PDD)?” Respondents who answered in the affirmative were then asked, “Does this child currently have the condition?” For ADHD, respondents were asked, “Has a doctor or other health care provider ever told you that this child has attention deficit disorder or attention-deficit/hyperactivity disorder, that is, ADD or ADHD?” This was followed by, “Does this child currently have the condition?” Children with current diagnoses of both ASD and ADHD were categorized as having ASD+ADHD. The reference groups were children with current ASD without co-occurring ADHD and children with current ADHD without co-occurring ASD. Children between the ages of 3 and 17 years were included in the analysis.
Comorbidities and treatments
Mental disorders examined in this study were anxiety, depression, or other mental health conditions (e.g., bipolar disorder); behavioral disorders examined were behavior or conduct problems; and developmental disorders were based on NSCH-derived categories of developmental delay, intellectual disability, speech or other language disorder, or learning disability. To assess current MBDDs, parents were asked if they were ever told by a doctor or other health care provider that the child had: anxiety problems, depression, or any other mental health condition. If they answered affirmatively, they were then asked whether the child currently had the condition. For other conditions (behavioral or developmental disorders), they were asked whether a doctor, other health care provider, or educator (including teachers and school nurses) had ever told them that the child had the disorder.
To assess behavior treatment, parents were asked, “At any time during the past 12 months, did this child receive behavioral treatment for autism, ASD, Asperger’s Disorder or PDD, such as training or an intervention that you or this child received to help with his or her behavior?” This question was not asked of children with ADHD without co-occurring ASD. Use of psychotropic medication was indicated if parents reported that: (a) a child with current ASD and/or ADHD was using medication; or (b) a child not on medication for ASD or ADHD has taken medication for other emotional, behavioral, or concentration issues during the past 12 months.
Covariates
Sociodemographic variables were included as covariates in adjusted analyses, informed by existing literature (Aylward et al., 2021; Durkin et al., 2017; Maenner et al., 2021; Shenouda et al., 2021; Shi et al., 2021; Sokolova et al., 2017; Xu et al., 2019; Young et al., 2020). Covariates included sex (Male, Female), age (3-7, 8-12, 13-17), race/ethnicity (White non-Hispanic, Black non-Hispanic, Hispanic, Multi-racial/Other non-Hispanic), presence of poverty based on family size and income (< 100% federal poverty level (FPL), 100-199% FPL, 200-399% FPL, ≥ 400% FPL), highest level of household educational attainment (Less than high school, High school/GED, Some college or technical school, College degree or higher), insurance type (Private only, Public only, Public and private, Currently uninsured), language spoken at home (English, Other than English), and child health status based on parents’ appraisal (Excellent/very good, Good, Fair/Poor). FPL is the ratio of total family income to the federal family poverty threshold. The following variables were imputed for missingness: sex (< 1%), race/ethnicity (≤ 1%), household educational attainment (≤ 3%), and poverty (~17%). Sex, race, and ethnicity were imputed using hot-deck imputation, while household educational attainment and FPL were multiply imputed using regression imputation (Data Resource Center for Child and Adolescent Health, 2021b).
Statistical analysis
Analyses were conducted using SAS statistical software survey procedures (Version 9.4; SAS Institute, Cary, NC) for complex study designs. Weighted proportions and 95% confidence intervals (CIs) were calculated for sociodemographic variables, health conditions, receipt of behavioral treatment, and current use of medication. Prevalence of sociodemographic and other characteristics was estimated for children with ASD+ADHD, children with ASD without co-occurring ADHD, and children with ADHD without co-occurring ASD. Bivariate associations between the diagnostic categories and the covariates, health conditions, receipt of behavioral treatment, and current use of psychotropic medication were examined using the Rao-Scott chi-square test for significance. Multivariable logistic regression models were used to estimate adjusted associations between ASD+ADHD status and each health condition, receipt of behavioral treatment, and current use of psychotropic medication. Additionally, logistic regression modeling was used to assess factors associated with receiving behavioral treatment and psychotropic medications among children with ASD+ADHD. Independent covariates included in the adjusted models were sex, age, race/ethnicity, household poverty, household educational attainment, insurance type, language spoken at home, and health status. The presence of any MBDD was also added as a covariate to the models examining receipt of behavioral treatment and current psychotropic medication use. Adjusted odds ratios (AOR) were computed from multivariable logistic regression models. Variance estimates were obtained using the Taylor series linearization method to account for sample weights and multistage sample design. Statistical significance was evaluated at the α level of .05.
Results
Among the estimated 1.7 million children in the U.S. with ASD in 2016-2018, 43.8% (95% CI 38.8, 48.9) had co-occurring ADHD. Among the estimated 5.3 million children in the U.S. with ADHD in 2016-2018, 13.9% (95% CI 12.1, 15.7) had co-occurring ASD. Children diagnosed with ASD+ADHD were older than children diagnosed with ASD without co-occurring ADHD (Table 1). While two-thirds (66.7%) of children with ASD without ADHD were ages 8 and older, eighty-five percent of children with ASD+ADHD were ages 8 and older. Children diagnosed with ASD+ADHD were more likely to be White non-Hispanic (54.0% vs 40.7%), and less likely to be Hispanic (25.8% vs. 35.7%) than children diagnosed with ASD without co-occurring ADHD. Compared with children with ADHD alone, children with ASD+ADHD were more likely to live in households with lower educational attainment and where English was not the predominant language. Children with ASD+ADHD also had lower prevalence of private-only insurance. The proportion of children reporting excellent or very good health was lower among those diagnosed with ASD+ADHD compared to children in both reference groups.
Table 1.
Characteristics of children with ASD, ADHD, and co-occurring ASD and ADHD.
| ASD+ADHD 95% (CI)a |
ASD without ADHD 95% (CI)a |
ADHD without ASD 95% (CI) |
|
|---|---|---|---|
| Sex | |||
| Male | 74.2 (66.5-81.9) | 81.1 (76.8-85.5) | 67.7 (65.4-70.0) |
| Female | 25.8 (18.1-33.5) | 18.9 (14.5-23.2) | 32.3 (30.0-34.6) |
| Age (yrs.) b | |||
| 3-7 | 14.6 (10.4-18.9) | 33.3 (26.7-39.9) | 12.4 (10.7-14.1) |
| 8-12 | 45.4 (38.2-52.7) | 33.1 (25.9-40.3) | 44.5 (42.1-46.9) |
| 13-17 | 40.0 (33.6-46.3) | 33.6 (26.2-41.0) | 43.1 (40.7-45.5) |
| Race/ethnicity b | |||
| White non-Hispanic | 54.0 (46.7-61.3) | 40.7 (34.4-46.9) | 57.8 (55.2-60.3) |
| Black non-Hispanic | 13.8 (9.0-18.5) | 13.5 (8.9-18.1) | 17.0 (14.8-19.2) |
| Hispanic | 25.8 (17.3-34.3)) | 35.7 (27.1-44.4) | 18.0 (15.7 (20.3) |
| Multi-racial/Other non-Hispanic | 6.5 (4.8-8.2) | 10.1 (7.5-12.8) | 7.3 (6.3-8.3) |
| Household poverty | |||
| < 100% FPL | 24.6 (19.2-30.0) | 29.6 (21.0-38.3) | 23.4 (21.1-25.7) |
| 100-199% FPL | 28.7 (20.7-36.8) | 25.1 (18.6-31.7) | >22.8 (20.6-25.0) |
| 200-399% FPL | 23.7 (18.5-29.0) | 23.6 (19.1-28.2) | 24.1 (22.3-26.0) |
| ≥400% FPL | 22.9 (18.5-27.4) | 21.6 (17.4-25.8) | 29.7 (27.7-31.6) |
| Household educational attainment c | |||
| Less than high school | 15.8 (7.9-23.7) | 8.1 (0.7-15.6) | 7.8 (5.5-9.9) |
| High school /GED | 21.3 (15.3-27.4) | 26.6 (19.6-33.6) | 23.5 (21.2-25.7) |
| Some college or technical school | 19.7 (15.4-24.0) | 23.8 (17.0-30.6) | 25.9 (24.0-27.8) |
| College degree or higher | 43.2 (36.6-49.8) | 41.5 (34.8-48.1) | 42.8 (40.6-45.1) |
| Insurance type c | |||
| Private only | 37.7 (31.3-44.0) | 40.0 (33.5-46.6) | 48.8 (46.5-51.2) |
| Public only | 44.8 (37.6-52.0) | 45.0 (37.0-52.9) | 39.6 (37.1-42.1) |
| Public and private | 12.7 (7.2-18.2) | 10.5 (7.7-13.3) | 6.9 (5.8-8.1) |
| Currently uninsured | 4.8 (2.2-7.5) | 4.5 (0.0-8.9) | 4.6 (3.5-5.8) |
| Language spoken at home c | |||
| English | 88.7 (80.0-97.4) | 84.1 (77.7-90.6) | 95.9 (94.3-97-5) |
| Other than English | 11.3 (2.6-20.0) | 15.9 (9.4-22.3) | 4.1 (2.5-5.7) |
| Health status b,c | |||
| Excellent/ very good | 54.2 (46.9-61.5) | 70.5 (62.1-78.9) | 79.2 (77.0-81.5) |
| Good | 35.4 (27.4-43.4) | 24.2 (15.6-32.8) | 16.3 (14.5-18.1) |
| Fair/Poor | 10.4 (6.6-14.2) | 5.5 (3.1-7.5) | 4.5 (2.8-6.1) |
Note: ADHD = attention-deficit/hyperactive disorder; ASD = autism spectrum disorder; CI = confidence interval; FPL = federal poverty level; GED = general equivalency diploma.
Percentages are weighted and may not total 100% in each category due to rounding.
Statistically significant at p<.05 or less for ASD without co-occurring ADHD compared with ASD+ADHD.
Statistically significant at p<.05 or less for ADHD without co-occurring ASD compared with ASD+ADH
Children with ASD+ADHD had higher prevalence of most of the MBDDs analyzed compared to children with ASD without co-occurring ADHD, and children with ADHD without co-occurring ASD (Table 2). Learning disability was the most commonly reported comorbid MBDD for children with ASD+ADHD (70.6%), whereas it was the third most reported condition among children with ASD without co-occurring ADHD (55.5%) and second for children with ADHD without co-occurring ASD (32.4%). Compared with children with ASD or ADHD alone, children with ASD+ADHD were also more likely to have behavior or conduct problems (69.6% vs. 36.8% and 46.0%, respectively), other mental health condition (59.8% vs. 41.1% and 29.6%, respectively), anxiety (60.0% vs. 25.1% and 29.2%, respectively), or depression (24.1% vs. 7.1% and 15.0%, respectively). Conversely, children with ASD+ADHD were less likely to have a speech or other language disorder (42.1% vs. 56.5%) compared with peers with ASD without co-occurring ADHD. The prevalence of developmental delay, intellectual disability, and receipt of behavioral treatment were similar among children with ASD+ADHD and those with ASD without ADHD.
Table 2.
Prevalence of co-occurring health conditions and treatments among children with ASD, ADHD, and ASD+ADHD.
| ASD+ADHD | ASD without ADHD | ADHD without ASD | |||
|---|---|---|---|---|---|
|
| |||||
| Health condition | (Weighted n=740,816) 95%(CI) |
(Weighted n=949,367) 95%(CI) |
AOR (95%CI)a,b | (Weighted n=4,570,320) 95%(CI) |
AOR (95%CI)a,c |
| Anxiety | 60.0 (52.8-67.3) | 25.1 (20.3-30.0) | 4.03 (2.77-4.87)*** | 29.2 (27.2-31.2) | 3.49 (2.65-4.61)*** |
| Depression | 24.1 (19.1-29.2) | 7.1 (4.4-9.9) | 3.08 (1.77-5.36)*** | 15.0 (13.4-16.5) | 1.67 (1.21-2.29)** |
| Behavior or conduct problems | 69.6 (62.2-76.9) | 36.8 (29.6-44.1) | 4.06 (2.72-6.06)*** | 46.0 (43.6-48.3) | 2.31 (1.68-3.17)*** |
| Other mental health condition | 59.8 (53.1-66.5) | 41.1 (34.6-47.6) | 2.05 (1.45-2.90)*** | 29.6 (27.5-31.7) | 3.08 (2.30-4.12)*** |
| Developmental delay | 60.5 (53.3-67.7) | 61.0 (53.2-68.8) | 0.91 (0.62-1.34) | 16.4 (14.8-18.0) | 7.34 (5.62-9.60)*** |
| Intellectual disability | 19.4 (14.7-24.1) | 17.5 (10.5-24.5) | 0.82 (0.50-1.34) | 2.8 (2.0-3.5) | 8.61 (5.42-13.70)*** |
| Speech or other language disorder | 42.1 (35.6-48.7) | 56.5 (49.5-63.6) | 0.64 (0.45-0.92)* | 10.1 (8.8-11.5) | 6.98 (5.14-9.49)*** |
| Learning disability | 70.6 (65.5-75.6) | 55.5 (48.3-62.6) | 1.73 (1.25-2.39)** | 32.4 (30.2-34.5) | 4.78 (3.69-6.20)*** |
|
| |||||
| Received behavioral treatment d,e | 59.9 (52.5-67.2) | 56.3 (48.7-63.9) | 1.16 (0.75-1.79) | N/A | N/A |
| Currently taking psychotropic medication f,e | 72.3 (64.9-79.6) | 15.6 (11.8-19.4) | 13.44 (8.97-20.14)*** | 69.4 (67.1-71.6) | 1.00 (0.70-1.43) |
Note: AOR = adjusted odds ratio; ADHD = attention-deficit/hyperactive disorder; ASD = autism spectrum disorder; CI = confidence interval; FPL = federal poverty level; GED = general equivalency diploma.
Modeling adjusted for sex, age, race/ethnicity, household poverty, household educational attainment, insurance type, language spoken at home, and health status.
Reference group = children with ASD without co-occurring ADHD.
Reference group = children with ADHD without co-occurring ASD
Children who received behavioral treatment for ASD in past 12 months.
Modeling adjusted for sex, age, race/ethnicity, household poverty, household educational attainment, insurance type, language spoken at home, health status, and mental, behavioral, and developmental disorders.
Children who were taking any medication for problems with emotions, concentration, or behavior, autism/ASD or ADD/ADHD, age 3-17 years
p<0.05,
p<0.01,
p<0.001
After adjustment with logistic regression models, we observed strong positive associations between health conditions and diagnosis of co-occurring ADHD among children with ASD. Compared with children with ASD without co-occurring ADHD, children with ASD+ADHD had higher odds of being diagnosed with anxiety (AOR 4.03 [95% CI 2.77, 4.87]), depression (AOR 3.08 [95% CI 1.77, 5.36]), behavior or conduct problems (AOR 4.06 [95% CI 2.72, 6.06]), other mental health condition (AOR 2.05 [95% CI 1.45, 2.90]), or learning disability (AOR 1.73 [95% CI 1.25, 2.39]). Nearly three-quarters (72.3%) of children with ASD+ADHD were taking psychotropic medication compared to 15.6% of children with ASD without co-occurring ADHD (AOR 13.44 [95% CI 8.97, 20.14]).
Further, compared to children with ADHD without ASD, children with ASD+ADHD had higher odds of anxiety (AOR 3.49 [95% CI 2.65, 4.61]), depression (AOR 1.67 [95% CI 1.21, 2.29]), behavior or conduct problems (AOR 2.31 [95% CI 1.68, 3.17]), and other mental health conditions (AOR 3.08 [95% CI 2.30, 4.12]). Likewise, the proportion of children with ASD+ADHD who had a speech or other language disorder was higher than that of children with ADHD without co-occurring ASD (42.1% vs.10.1%, AOR 6.98 [95% CI 5.14, 9.49]). The odds of developmental delay (AOR 7.34 [95% CI 5.62, 9.60]), intellectual disability (AOR 8.61 [95% CI 5.42, 13.70]), and learning disability (AOR 4.78 [95% CI, 3.69, 6.20]) were also greater among this group. However, the prevalence of psychotropic medication use was similar for children with ADHD with and without ASD (69.4% [95% CI 67.1, 71.6], AOR 1.00 [95% CI 0.70, 1.43]).
Correlates of receiving behavioral treatment and current psychotropic medication among children with ASD+ADHD are presented in Table 3. Males had greater odds of receiving behavioral treatment than females (AOR 3.02 [95% CI 1.65, 5.53]). Receipt of behavioral treatment was less likely reported for children aged 13-17 than children aged 3-7 (AOR 0.42 [95% CI 0.20, 0.87]) as well as among children living in households with less than high school educational attainment (AOR 0.27 [95% CI 0.10, 0.74]). In contrast to the findings for behavioral treatment, medication use was more likely reported for children aged 8-12 years (AOR 3.48 [95% CI 1.61, 7.53]) and those aged 13–17 years (AOR 2.92 [95% CI 1.29, 6.65]) compared to younger children. Children living in lower-income households were less likely to report medication use compared to households ≥ 400% FPL (AOR 0.28-0.59). Compared with children with private insurance alone, psychotropic medication use was substantially more likely among children with combined public and private insurance (AOR 10.95 [95% CI 2.73, 43.98]). Children with MBDDs were also more likely to take psychotropic medication (AOR 3.81 [95% CI 1.18,12.29]).
Table 3.
Correlates of receiving behavioral treatment and psychotropic medication for children with co-occurring ASD+ADHDa.
| Characteristics | Received Behavioral Treatmentb (Weighted n=439,922) |
Currently Taking Medicationc (Weighted n=535,163) |
|---|---|---|
| AOR (95% CI) | AOR (95% CI) | |
| Sex | ||
| Male | 3.02 (1.65-5.53)*** | 1.07 (0.52-2.19) |
| Female | REF | REF |
| Age (yrs.) | ||
| 3-7 | REF | REF |
| 8-12 | 0.60 (0.28-1.26) | 3.48 (1.61-7.53)** |
| 13-17 | 0.42 (0.20-0.87)* | 2.92 (1.29-6.65)* |
| Race/ethnicity | ||
| White non-Hispanic | REF | REF |
| Black non-Hispanic | 0.60 (0.29-1.27) | 1.18 (0.47-2.95) |
| Hispanic | 0.65 (0.28-1.49) | 0.55 (0.24-1.26) |
| Multi-racial/Other non-Hispanic | 1.41 (0.66-3.03) | 1.32 (0.65-2.71) |
| Household poverty | ||
| < 100% FPL | 1.50 (0.62-3.62) | 0.33 (0.11-1.02) |
| 100-199% FPL | 0.62 (0.30-1.30) | 0.28 (0.12-0.69)** |
| 200-399% FPL | 0.58 (0.31-1.11) | 0.59 (0.28-1.22) |
| ≥400% FPL | REF | REF |
| Household educational attainment | ||
| Less than high school | 0.27 (0.10-0.74)* | 0.69 (0.22-2.16) |
| High school /GED | 0.98 (0.46-2.10) | 1.62 (0.67-3.92) |
| Some college or technical school | 1.10 (0.59-2.04) | 1.11 (0.53-2.30) |
| College degree or higher | REF | REF |
| Insurance type | ||
| Private only | REF | REF |
| Public only | 1.26 (0.68-2.33) | 2.15 (0.92-5.05) |
| Public and private | 1.98 (0.86-4.54) | 10.95 (2.73-43.98)*** |
| Currently uninsured | 1.71 (0.47-6.23) | 0.82 (0.21-3.17) |
| Language spoken at home | ||
| English | REF | REF |
| Other than English | 1.29 (0.34-4.87) | 0.39 (0.08-1.79) |
| Health status | ||
| Excellent/ very good | REF | REF |
| Good | 1.35 (0.77-2.36) | 1.43 (0.72-2.81) |
| Fair/Poor | 1.47 (0.64-3.40) | 1.29 (0.46-3.67) |
| Mental, behavioral, and developmental disorders | ||
| Yes | 1.43 (0.43-4.75) | 3.81 (1.18-12.29)* |
| No | REF | REF |
Note: AOR = adjusted odds ratio; ADHD = attention-deficit/hyperactive disorder; ASD = autism spectrum disorder; CI = confidence interval; FPL = federal poverty level; GED = general equivalency diploma; REF = reference.
Modeling adjusted for sex, age, race/ethnicity, household poverty, household educational attainment, insurance type, language spoken at home, health status, and mental, behavioral, and developmental disorders.
Children who received behavioral treatment for ASD in past 12 months.
Children who were taking any medication for problems with emotions, concentration, or behavior, ASD or ADHD, age 3-17 years.
p<0.05,
p<0.01,
p<0.0
The independent associations between sociodemographic and health-related characteristics and mental and behavioral disorders among children with ASD+ADHD are presented in Table 4. Older age, reporting combined public and private or currently uninsured, and having poorer health were associated with higher odds of anxiety and depression. In contrast, mood disorders were less likely associated with living in a household with lower educational attainment or where English was not the predominant language. An inverse relationship was observed between age and reported behavior or conduct problems. Children with combined public and private health insurance had higher odds for all of the mental and behavioral disorders. Children who were older or from lower FPL households were less likely to have developmental delay or speech or other language disorder (Table 5). In general, poorer health was associated with higher likelihood of developmental disorders. Of note, males had twice the odds of speech or other language disorder compared to females (AOR 2.17 [95% CI 1.08, 3.97]) while Hispanic children had nearly three times the odds of the disorder (AOR 2.89 [95% CI 1.24, 6.69]). Racial and ethnic differences were also noted with higher odds of learning disability for Black non-Hispanic children compared to White non-Hispanic children (AOR 2.46 [95% CI 1.09, 5.53]).
Table 4.
Correlates of mental and behavioral disorders among children with ASD+ADHDa.
| Characteristics | Anxiety AOR (95% CI) |
Depression AOR (95% CI) |
Other mental health conditionb AOR (95% CI) |
Behavior or conduct problems AOR (95% CI) |
|---|---|---|---|---|
| Sex | ||||
| Male | 1.05 (0.57-1.96) | 0.98 (0.54-1.79) | 0.98 (0.51-1.85) | 1.45 (0.80-2.63) |
| Female | REF | REF | REF | REF |
| Age (yrs.) | ||||
| 3-7 | REF | REF | REF | REF |
| 8-12 | 2.05 (0.97-4.33) | 4.83 (1.49-15.64)** | 1.51 (0.74-3.07) | 0.44 (0.19-1.02) |
| 13-17 | 2.27 (1.06-4.86)* | 9.26 (3.06-28.09)*** | 1.55 (0.75-3.23) | 0.15 (0.64-0.34)*** |
| Race/ethnicity | ||||
| White non-Hispanic | REF | REF | REF | REF |
| Black non-Hispanic | 0.76 (0.33-1.75) | 0.96 (0.39-2.41) | 1.13 (0.50-2.52) | 1.59 (0.67-3.81) |
| Hispanic | 1.41 (0.66-3.04) | 0.99 (0.42-2.31) | 0.63 (0.29-1.37) | 0.66 (0.33-1.33) |
| Multi-racial/Other non-Hispanic | 0.90 (0.45-1.79) | 0.93 (0.45-1.94) | 0.94 (0.50-1.79) | 1.34 (0.65-2.76) |
| Household poverty | ||||
| < 100% FPL | 1.57 (0.63-3.93) | 1.48 (0.61-3.60) | 0.66 (0.30-1.47) | 0.83 (0.32-2.16) |
| 100-199% FPL | 1.14 (0.55-2.34) | 1.19 (0.54-2.60) | 0.66 (0.34-1.30) | 0.51(0.25-1.06) |
| 200-399% FPL | 1.06 (0.56-2.02) | 0.66 (0.33-1.35) | 0.95 (0.51-1.77) | 0.57 (0.30-1.09) |
| ≥400% FPL | REF | REF | REF | REF |
| Household educational attainment | ||||
| Less than high school | 0.20 (0.07-0.57)** | 0.27 (0.08-0.92)* | 1.04 (0.39-2.81) | 1.58 (0.55-4.48) |
| High school /GED | 0.74 (0.34-1.16) | 0.40 (0.19-0.84)* | 1.11 (0.56-2.20) | 1.14 (0.53-2.48) |
| Some college or technical school | 0.83 (0.45-1.54) | 0.96 (0.50-1.84) | 1.06 (0.58-1.93) | 1.99 (1.03-3.84)* |
| College degree or higher | REF | REF | REF | REF |
| Insurance type | ||||
| Private only | REF | REF | REF | REF |
| Public only | 1.65 (0.88-3.12) | 1.93 (0.98-3.80) | 1.59 (0.84-2.99) | 1.14 (0.60-2.18) |
| Public and private | 3.06 (1.29-7.26)* | 2.37 (1.12-5.04)* | 3.34 (1.60-6.97)** | 4.36 (1.50-12.69)** |
| Currently uninsured | 3.59 (1.24-10.38)* | 1.59 (0.47-5.45) | 0.76 (0.23-2.50) | 0.74 (0.18-3.00) |
| Language spoken at home | ||||
| English | REF | REF | REF | REF |
| Other than English | 0.16 (0.04-0.56)** | 0.09 (0.02-0.59)* | 2.48 (0.59-10.31) | 0.21 (0.05-0.83)* |
| Health status | ||||
| Excellent/ very good | REF | REF | REF | REF |
| Good | 3.21 (1.74-5.94)*** | 3.40 (1.88-6.14)*** | 1.46 (0.80-2.66) | 2.43 (1.31-4.52)** |
| Fair/Poor | 1.24 (0.58-2.63) | 4.03 (1.77-9.16)*** | 0.77 (0.33-1.76) | 10.47 (3.33-32.96)*** |
Note: AOR = adjusted odds ratio; ADHD = attention-deficit/hyperactive disorder; ASD = autism spectrum disorder; CI = confidence interval; FPL = federal poverty level; GED = general equivalency diploma; REF = reference.
Modeling adjusted for all listed characteristics.
Mental health conditions other than anxiety or depression.
p<0.05,
p<0.01,
p<0.001.
Table 5.
Correlates of developmental disorders among children with ASD+ADHD.
| Characteristics | Developmental delay AOR (95% CI) |
Intellectual disability AOR (95% CI) |
Learning disability AOR (95% CI) |
Speech or other language disorder AOR (95% CI) |
|---|---|---|---|---|
| Sex | ||||
| Male | 1.59 (0.89-2.84) | 0.91 (0.45-1.82) | 0.84 (0.49-1.44) | 2.07 (1.08-3.97)* |
| Female | REF | REF | REF | REF |
| Age (yrs.) | ||||
| 3-7 | REF | REF | REF | REF |
| 8-12 | 0.43 (0.21-0.91)* | 1.48 (0.58-3.77) | 0.98 (0.49-1.94) | 0.55 (0.29-1.08) |
| 13-17 | 0.37 (0.18-0.77)** | 1.28 (0.55-2.98) | 0.90 (0.47-1.74) | 0.43 (0.22-0.84)* |
| Race/ethnicity | ||||
| White non-Hispanic | REF | REF | REF | REF |
| Black non-Hispanic | 1.88 (0.83-4.25) | 2.00 (0.90-4.43) | 2.46 (1.09-5.53)* | 1.63 (0.79-3.39) |
| Hispanic | 0.92 (0.42-1.98) | 1.88 (0.78-4.51) | 2.00 (0.88-4.58) | 2.89 (1.24-6.69)* |
| Multi-racial/Other, non-Hispanic | 0.82 (0.45-1.51) | 0.76 (0.37-1.57) | 0.92 (0.50-1.70) | 0.71 (0.38-1.32) |
| Household poverty | ||||
| < 100% FPL | 0.40 (0.18-0.89)* | 0.39 (0.12-1.20) | 0.93 (0.43-2.01) | 0.52 (0.23-1.17) |
| 100-199% FPL | 0.45 (0.22-0.90)* | 0.34 (0.11-1.01) | 0.64 (0.34-1.20) | 0.31 (0.14-0.66)** |
| 200-399% FPL | 0.65 (0.36-1.18) | 0.94 (0.44-1.98) | 0.71 (0.40-1.28) | 0.68 (0.36-1.28) |
| ≥400% FPL | REF | REF | REF | REF |
| Household educational attainment | ||||
| Less than high school | 0.60 (0.22-1.68) | 0.62 (0.15-2.64) | 2.02 (0.63-6.51) | 0.87 (0.32-2.35) |
| High school /GED | 2.46 (1.20-5.05)* | 1.80 (0.82-3.94) | 1.89 (0.92-3.87) | 1.08 (0.53-2.18) |
| Some college or technical school | 1.38 (0.77-2.47) | 2.14 (1.08-4.24)* | 1.27 (0.73-2.22) | 1.34 (0.76-2.36) |
| College degree or higher | REF | REF | REF | REF |
| Insurance type | ||||
| Private only | REF | REF | REF | REF |
| Public only | 1.58 (0.81-3.10) | 3.20 (1.43-7.16)** | 1.20 (0.66-2.16) | 2.04 (1.06-3.89)* |
| Public and private | 2.02 (0.97-4.20) | 1.74 (0.77-3.90) | 0.79 (0.42-1.48) | 1.47 (0.70-3.06) |
| Currently uninsured | 1.93 (0.52-7.10) | 1.83 (0.46-7.30) | 0.63 (0.16-2.46) | 1.84 (0.52-6.54) |
| Language spoken at home | ||||
| English | REF | REF | REF | REF |
| Other than English | 0.82 (0.20-3.30) | 0.45 (0.09-2.32) | 4.02 (0.55-29.22) | 0.63 (0.15-2.63) |
| Health status | ||||
| Excellent/ very good | REF | REF | REF | REF |
| Good | 1.87 (1.07-3.26)* | 1.63 (0.82-3.21) | 1.62 (0.96-2.75) | 0.91 (0.52-1.61) |
| Fair/Poor | 3.27 (1.17-9.11)* | 3.55 (1.60-7.88)** | 2.98 (1.15-7.73)* | 1.52 (0.68-3.41) |
Note: AOR = adjusted odds ratio; ADHD = attention-deficit/hyperactive disorder; ASD = autism spectrum disorder; CI = confidence interval; FPL = federal poverty level; GED = general equivalency diploma; REF = reference.
Modeling adjusted for all listed characteristics.
p<0.05,
p<0.01
Discussion
In a nationally representative sample, children with co-occurring ASD and ADHD were far more likely to have many other comorbid MBDDs than children with either ASD or ADHD alone, including mental health problems and behavior or conduct problems. Unlike children with ASD without ADHD, a majority of children with ASD+ADHD received psychotropic medications, although rates of behavioral treatments were similar between groups. In contrast, psychotropic medication use was overall similar between children with ASD+ADHD and children with ADHD alone. Among children with ASD+ADHD, males were more likely to receive behavioral treatment. However, older children and adolescents were less likely to receive behavioral treatment but were more likely to take psychotropic medication.
Our findings are consistent with studies in smaller clinical and research samples showing a higher prevalence of anxiety, mood disorders, and other mental health conditions among children with ASD+ADHD (Dellapiazza et al., 2021; Gadow et al., 2009; Gordon-Lipkin et al., 2018; Hong et al., 2021; Jang et al., 2013; Mulligan et al., 2009; Rao & Landa, 2013). They are also supported by a nationally representative study of the treatment needs among children with an ADHD diagnosis who also had an ASD diagnosis (Zablotsky et al., 2017). Our study found a strong association between older age and anxiety and depression among children with ASD+ADHD. Previous research has indicated increasing age as a significant contributor to the presence of anxiety disorder and mood disorders in this population (Gordon-Lipkin et al., 2018). In addition, a disparity in language spoken at home was found whereby children from non-English speaking homes had lower likelihood of mental and behavioral disorders. This may suggest lower screening rates in immigrant populations and is worthy of further investigation. Mental health disorders are treatable, and because children with ASD+ADHD are vulnerable to these disorders, mental health screening and services should be part of the treatment plan for children presenting with ASD+ADHD. This is particularly true for older children and adolescents with ASD+ADHD, who are at increased risk.
Several studies have found higher rates of attention problems, aggression, repetitive behaviors, tantrum behavior, avoidant behavior, conduct problems, oppositional defiant disorder, and other externalizing problems in children with ASD+ADHD (Gadow et al., 2009; Hong et al., 2021; Jang et al., 2013; Mulligan et al., 2009; Sikora et al., 2012). Results from our analyses are aligned with those findings. We also found that children with combined public and private insurance had higher odds of mental health conditions and behavior or conduct problems and were substantially more likely to receive psychotropic medication, potentially suggesting higher acuity of these disorders which may have motivated decisions to acquire co-insurance. Higher odds of mental health conditions among children with combined public and private insurance may also indicate greater access to mental health care in this population, as many states provide disability-related Medicaid eligibility pathways for children with special health care needs.
Prior research has suggested a positive correlation between severity of behavior and conduct problems and severity of ADHD symptoms among children with ASD (Hong et al., 2021). Analogously, the greater the number of ASD symptoms present in children with ADHD, the more severe behavior and conduct problems tend to be (Mulligan et al., 2009). Relatedly, it has been hypothesized that ASD+ADHD is a specific subtype of ADHD with specific phenotypic characteristics (Mulligan et al., 2009). Another theory suggests that there are some common genetic influences between autistic traits and ADHD behaviors (Ronald et al., 2008). Further research is needed to explore these and other hypotheses. These relationships also have important clinical implications for the management of complex behavioral symptoms, which may warrant specialized medical, psychoeducational, and behavioral interventions.
Compared to children with ADHD alone, children with ASD+ADHD had higher prevalence of all developmental disorders measured. Children with ASD+ADHD were also more likely to have a learning disorder than children with ASD alone, though no significant differences were found in prevalence of developmental or intellectual disability between the two groups, in contrast to prior studies from clinical and research samples (Mulligan et al., 2009; Rao & Landa, 2013; Sikora et al., 2012; Zablotsky et al., 2017). Moreover, prior studies have found children with ASD+ADHD were more likely to have significant language impairment than peers with ASD without co-occurring ADHD, whereas our study found the opposite. Two-fifths (42.1%) of children with ASD+ADHD in this nationally representative sample reported speech or other language disorder, while more than half (56.5%) of children with ASD without co-occurring ADHD had the condition. Variations in the way developmental disorders were operationally defined and measured by individual studies, including the NSCH, may have contributed to this discrepancy. For example, one study using data from a nationally representative sample examined developmental disorders by combining intellectual disability, learning disorder, and language disorder into a single category (Zablotsky et al., 2017). Limitations on the generalizability of previous research and the possibility of selection bias may also explain some of these differences.
Children with ASD with and without ADHD received behavioral treatment at similar rates, even though children with ASD+ADHD have more comorbid behavior or conduct problems, and hence more behavioral treatment needs. This finding may suggest an unmet need for behavioral treatment in the care of these children (Young et al., 2020; Zablotsky et al., 2017). It is essential that future studies examine barriers and facilitators associated with treatment access and utilization in this population. A possible explanation for the low prevalence of behavioral treatment is that behavior and conduct problems are being addressed predominantly with medication; we found that nearly three-quarters of children with ASD+ADHD were currently taking medication compared to 15.6% of children with ASD without co-occurring ADHD. According to recent guidelines, pharmacological intervention in children with ASD+ADHD should be preceded by behavioral observation and psychological intervention as first-line treatment. If psychological/environmental interventions are unsuccessful, then supplemental ADHD medication is indicated (Young et al., 2020).
Among children with ASD+ADHD, males were more likely to report receiving behavioral treatment, which may suggest greater severity of symptoms. Although older children and adolescents had lower odds of receiving behavioral treatment, they were more likely to take psychotropic medications similar to children with public and private insurance. Importantly, no significant differences in medication use were found between children with ASD+ADHD and those with ADHD alone. This may indicate that medication is being used primarily to manage symptoms associated with ADHD (e.g., inattention, hyperactivity, impulsivity, aggression, irritability, anxiety, mood disorders and sleep disturbance). Moreover, there are no recommended pharmacological treatments for core symptoms of ASD (Young et al., 2020).
Strengths of our study include the use of multiyear data from a large, diverse, nationally representative sample to examine MBDDs, receipt of behavioral treatments, and use of psychotropic medication among children diagnosed with ASD with and without co-occurring ADHD and children with ADHD with and without ASD. Representative samples result in stronger external validity, and as such, findings can be generalized with confidence to the general U.S. population (Bernard, 2012; Bryman, 2016). Additionally, we identified novel factors associated with MBDDs and treatments among children with ASD+ADHD, including children’s age, gender, health insurance, and language spoken at home.
However, there were also methodological limitations. First, the study is cross-sectional, and causality cannot be inferred. Second, NSCH data are self-reported, which may be subject to recall or social desirability bias. Third, diagnoses and treatments were not independently verified with clinical evaluations or other data. Fourth, findings may be influenced by nonresponse bias, although weighting procedures were employed to adjust for nonresponse (Data Resource Center for Child and Adolescent Health, 2021b). Additionally, there is a high level of consistency between results of the NSCH and other nationally representative surveys in estimating developmental disabilities including ASD (Kogan et al., 2018; Zablotsky et al., 2019). Finally, there may be some symptom overlap across ASD and ADHD which can complicate clinical assessment, even among verbally fluent children (Grzadzinski et al., 2016; Young et al., 2020).
In conclusion, our population-based study presents novel epidemiologic insights into the clinical characteristics and management profiles of children with comorbid ASD+ADHD. Given the rising prevalence of both ADHD and ASD, our findings have important implications for both public health policy and clinical care. Further research is necessary to explore the many disparities documented in this study, including in rates of mental and behavioral disorders, particularly among non-English-speaking households. Lastly, in regard to traditional categorical classification of diagnostic system, our study highlights future clinical and research directions for examining the overlapping features and dimensional aspects of both conditions and their associated developmental and psychopathological features.
Acknowledgement:
The authors thank Lawrence C. Kleinman, MD, MPH of the Division of Population Health, Quality, and Implementation Sciences, Department of Pediatrics, Robert Wood Johnson Medical School, Rutgers University, for his comments.
Funding/Support:
Efforts by Myriam Casseus were supported by a grant (U3DMD32755-01-00) from the U.S. Department of Health and Human Services Health Resources and Services Administration (HRSA). Daniel B Horton was supported by grants (UL1TR003017, R01HD109335) from the National Institutes of Health.
Role of Funder/Sponsor:
The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding organization.
Disclosures:
Daniel B Horton has received research funding from Danisco USA, Inc, unrelated to the current work.
Footnotes
Conflict of Interest: The authors have no conflicts of interest to disclose.
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