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. Author manuscript; available in PMC: 2016 Jun 1.
Published in final edited form as: J Autism Dev Disord. 2015 Jun;45(6):1836–1844. doi: 10.1007/s10803-014-2342-0

The Relationship Between Autistic Symptomatology and Independent Living Skills in Adolescents and Young Adults with Fragile X Syndrome

Kristin M Hustyi 1, Scott S Hall 1,§, Eve-Marie Quintin 1, Lindsay C Chromik 1, Amy A Lightbody 1, Allan L Reiss 1
PMCID: PMC4548879  NIHMSID: NIHMS650114  PMID: 25518824

Abstract

Few studies have examined the relationship between autistic symptomatology and competence in independent living skills in adolescents and young adults with fragile X syndrome (FXS). In this study, 70 individuals with FXS, aged 15 to 25 years, and 35 age- and IQ-matched controls were administered the Independent Living Scales (Loeb, 1996) and the Autism Diagnostic Observation Schedule (Lord et al., 2000). Results showed that higher levels of autistic symptomatology were associated with lower levels of competence in independent living skills in individuals with FXS, but not in controls. These data indicated that the relationship between autistic symptomatology and independent living skills was syndrome-specific. Early intervention strategies that address autistic symptomatology are sorely needed to improve functional outcomes in this population.

Keywords: fragile X syndrome, functional skills, independent living skills, autistic symptomatology

Individuals with fragile X syndrome (FXS) appear to have a normal life expectancy (Coppus 2013; Sabaratnam 2000; Partington et al. 1992) and therefore, caregivers need to make long-term plans to address their needs. Yet relatively few studies have been published on the adult lives of individuals with FXS. FXS is caused by an expansion of >200 CGG trinucleotide repeats on the fragile X mental retardation gene (FMR1) on the long arm of the X chromosome and affects approximately 1 in 4000 individuals worldwide (Turner et al. 1996). Many individuals with FXS present with cognitive and behavioral abnormalities, of which impairments in communication, reciprocal social interaction, and restricted and repetitive behaviors – the defining features of autism spectrum disorder (ASD) – are common (Brock and Hatton 2010; Harris et al. 2008; Kau et al. 2004; Kaufmann et al. 2004; McCary and Roberts 2013; Wolff et al. 2012). As such, FXS is the leading known single-gene risk factor for ASD.

An appreciable body of research has focused on the presence of autistic features in FXS, revealing considerable variability in the presence of autistic-like symptomatology in this population throughout the lifespan (Cornish et al. 2012; Hagerman et al. 1986; Hall et al. 2008; Hernandez et al. 2009; Hessl et al. 2001; McDuffie et al. 2010). The reported prevalence of autism in FXS populations ranges from 25% to 67% (Bailey et al. 1998; Clifford et al. 2007; Demark et al. 2003; Harris et al. 2008; Hatton et al. 2006; Kaufmann et al. 2004; Rogers et al. 2001), with longitudinal data suggesting that autistic behavior increases slowly but significantly over time (Hatton et al. 2006). Heterogeneity is further augmented by sex differences, given that males with FXS have only one X chromosome and therefore present with more severe impairments. Given that females have two X chromosomes, females with FXS generally have fewer symptoms due to X inactivation patterns.

Recently, researchers have begun to explore how particular behavioral profiles relate to competence in functional and independent living skills in FXS. For example Bailey et al. (2009) asked the caregivers of individuals with FXS to rate their child's functional and independent living skills (e.g., eating, dressing, toileting, bathing and hygiene, communication, articulation, and reading skills) using one of four possible classifications: does not perform this task, does this task but not well, does this task fairly well, or does this task very well, to describe their child's behavior (e.g., overall thinking, reasoning, learning ability, mood, ability to adapt to new situations, and ability to listen and pay attention) and report if their child had been diagnosed or treated for any co-occurring disorders (e.g., attention problems, hyperactivity, autism, seizures, anxiety, etc.). By adulthood, the majority of individuals with FXS aged 20 years and older had mastered many basic independent living skills (e.g., eating, bathing, and toileting). Overall thinking, reasoning, adaptability, and attention were all predictive of skill level, as was the total number of co-occurring disorders. However, because co-occurring conditions were coded dichotomously (e.g., 0 = 5 or more co-occurring disorders, 1 = fewer than five co-occurring disorders), little was revealed about the relationship between independent living skills and specific disorders.

Similarly, Hartley et al. (2011) reported on the functional and independent living skills of individuals with FXS. The rating scale and items used to assess functional and independent living skills were identical to Bailey et al. (2009). Overall, the results from Hartley et al.'s survey corroborated Bailey et al., highlighting that competence with functional and independent living skills were highly predictive of actual independence (i.e., a composite measure of scores in domains related to residence, employment, assistance with everyday life, friendship, and leisure), especially in males with FXS, and that the presence of co-occurring disorders was predictive of less independence in adult life. Specifically, the presence of ASD was an important predictor of independence in males, even after controlling for functional skills.

The results of these investigations suggest that the degree of autistic symptomatology may play a crucial role in functional skill level, and ultimately in the independence of adults with FXS. However, these findings were only partially supported by Smith et al. (2012). Smith and colleagues found that, although adolescents and adults with FXS who also met criteria for autism exhibited higher levels of repetitive and challenging behaviors than individuals with “FXS only” and individuals with “autism only”, they were not statistically different from the group of individuals with “FXS only” with respect to daily living skills, i.e., total score from parent ratings on the Revised Adaptive Daily Living Index (Seltzer and Krauss 1989). However, individuals with “autism only” evidenced significantly lower levels of independence in activities of daily living than either group of individuals with FXS. Therefore the impact of autistic symptomatology on functional or independent living skills in FXS is still unclear.

A critical limitation of these studies concerns the reliance on indirect caregiver report of skill level. Studies comparing direct and indirect methods of assessing functional and independent living skills in other populations have found direct assessments to be superior to indirect methods, which tend to under- or overestimate skill level (Karagiozis et al. 1998; Loewenstein et al. 1989; Reuben et al. 1995; Rozzini et al. 1993). Given that previous analyses have employed indirect methods only and have produced mixed results, an examination of competence in independent living skills in older adolescents and young adults with FXS using direct assessment methods is clearly warranted to understand how autistic symptomatology might be associated with functional outcomes in adulthood. Furthermore, to our knowledge, competence in independent living skills in individuals with FXS has not been compared to age, IQ and autism-matched controls. Thus, the degree to which the profile of independent living skills in FXS differs from controls, and whether the relationship between autistic symptomatology and competence in independent living skills is specific to FXS, is unknown. Using the Independent Living Scales (Loeb 1996), a direct assessment of competence in independent living skills, and the Autism Diagnostic Observation Schedule (Lord et al. 2000), the “gold standard” instrument for assessing autistic symptomatology, the current study sought to answer the following questions: (a) What proportion of adolescent and young adults with FXS demonstrate competency for independent to semi-independent living status? (b) How do individuals with FXS compare to age, IQ and autism-matched controls with respect to the profile of independent living skills? (c) What is the relationship between autistic symptomatology and independent living skills in adolescents and young adults with FXS?

Method

Participants

Participants were recruited as part of an NIH-funded longitudinal study investigating functional outcomes and neuroimaging of adolescents and young adults with FXS conducted at Stanford University. Participants with FXS were recruited via advertisements, community media, and state chapters of the National Fragile X Foundation. Individuals with FXS were included in the present study if they were aged between 15 and 25 years inclusive, had a confirmed diagnosis of FXS (i.e., evidence of aberrant methylation on the FMR1 gene) by Southern Blot DNA analysis (Kimball Genetics, Inc.), and could travel to Stanford University for a 2-day assessment. Control participants were recruited via community media and state-run agencies for individuals with developmental disabilities in the local area (e.g., Regional Centers in California). Exclusion criteria in both groups included prematurity (<34 weeks gestation), low birth weight (<2000g), the presence of sensory impairments, or any other serious medical or neurological condition that affected growth or development (e.g., seizure disorder, diabetes, congenital heart disease). Control participants were screened for FXS to confirm that they did not have FXS and none of the controls had a diagnosis of a known genetic disorder associated with intellectual impairment (e.g., Down syndrome, Prader-Will-syndrome, Smith-Magenis syndrome).

In order to match the groups in terms of age and IQ, we recruited controls in the same age range (15 to 25 years) who had a similar range of IQ's (40 to 120). However, there was a trend for the FXS group to have higher levels of autistic symptomatology. To balance the groups in terms of degree of autistic symptomatology, 7 males with FXS who received the highest scores on the Autism Diagnostic Observation Schedule (ADOS) were subsequently excluded from the study. Seventy individuals with FXS (35 male, 35 female), aged 15 to 25 years, and 35 controls (16 male, 19 female) therefore participated in the present study. Table 1 shows the demographic characteristics of the two groups.

Table 1.

Demographic characteristics of the sample. Means (and SD's) are shown for age, IQ and autistic symptomatology.

FXS (N=70) Controls (N=35) X2/t p
Sex (M, F) 35, 35 16, 19 .17 .68
Age (years) 20.57 (3.09) 19.60 (3.01) 1.55 .12
IQ1
 Verbal IQ 72.16 (20.47) 75.26 (18.27) .76 .45
 Performance IQ 68.34 (18.88) 74.60 (18.66) 1.61 .11
 Full scale IQ 67.76 (20.64) 72.74 (18.86) 1.20 .23
Autistic symptoms2
 ADOS Communication 1.90 (1.75) 1.48 (1.67) 1.10 .27
 ADOS Social Interaction 4.72 (3.33) 4.23 (3.11) .70 .49
 ADOS Total score 6.65 (4.63) 5.71 (4.44) .95 .35
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1

Wechsler Abbreviated Scale of Intelligence (Wechsler 1999) for participants aged 17 years or older and Wechsler Intelligence Scale for Children-Third Edition (Wechsler 1991) for participants under 17 years of age.

2

Autism Diagnostic Observation Schedule (ADOS) (Lord et al., 2000).

As shown in Table 1, control participants were well matched to participants with FXS in terms of sex, age, IQ and autistic symptomatology. As expected for an X-linked genetic disorder, male participants with FXS obtained significantly lower IQ scores (M = 55.17, SD = 8.04) than female participants with FXS (M = 80.34, SD = 21.77), (t(68) = 6.42, p < .001). Males with FXS also showed higher levels of autistic symptomatology (M = 9.24, SD = 3.94) than female participants with FXS (M = 4.06, SD = 3.76), (t(68) = 5.54, p < .001). There were no differences in age between male and female participants with FXS and there were no differences in age, IQ or autistic symptomatology between male and female controls.

Measures

Independent Living Skills

The Independent Living Scales (ILS; Loeb 1996) is a direct assessment of functional and independent living skills designed to facilitate competency evaluations in aging populations and adults in clinical populations who may be experiencing cognitive impairments, such as intellectual disability, traumatic brain injury, and dementia. The assessment lasts approximately 45 minutes, during which the researcher or clinician engages the individual in a number of activities designed to assess competence for independent living skills. The ILS contains 70 items with five subscales, two factors, and a total score. All items are scored on a scale from 0 to 2, with a score of 2 indicating proficiency with the skill, 1 indicating partial proficiency and 0 indicating inability to demonstrate the skill. The Memory/Orientation subscale has 8 items and includes questions such as, “What time does this clock show?”, “What is your telephone number?”, and requires the participant to remember a shopping list and details about a doctor's appointment. The Money Management subscale has 17 items and includes questions such as, “By what date do you have to file your personal tax return?”, “About how much does a loaf of bread cost?” and assesses how well participants are able to count change, write out a check to pay a bill, and balance a checkbook. The Managing a Home and Transportation subscale has 15 items and includes questions such as, “Why do we need keys?”, “What kind of information can you get from a bus schedule?”, and requires the participant to address an envelope, use a telephone book, and dial a telephone number. The Health and Safety subscale has 20 items including questions such as, “What would you do if you were outside and saw smoke coming out of your kitchen window?”, “What would you do if you were home alone and there was a knock on your door late at night?”, and requires the participant to demonstrate how to call the police, explain why it is important to know the side effects of medication and why bathing is important. Finally, the Social Adjustment subscale has 10 items that requires the participant to rate how they feel about themselves, if they are angry with others, and if they have suicidal thoughts. This subscale also contains items requiring the participant to list things that he or she values in life, describe how often they talk with and see friends, and explain why it is important to have friends.

The two ILS factors, Problem Solving (33 items) and Performance/Information (21 items) are derived from a factor analysis of the items on the five subscales and provide additional clinical information. The Problem Solving subscale comprises items that require knowledge of relevant facts as well as ability in abstract reasoning and problem solving (e.g., getting repairs made to home, precautions to take when bathing, sources of income, etc.). The Performance/Information subscale comprises items that require general knowledge, short-term memory, and the ability to perform simple, everyday tasks (e.g., paying bills, calculating a deductible, reading maps, etc.).

Raw scores and standard T-scores can be computed for the subscales and factors as well as a standard Full Scale score. The standard Full Scale T-score has a mean of 100, and an SD of 15 (with scores ranging from 55 to 115). Standard Full Scale T-scores greater than 1 SD below the mean (i.e., 55 to 84) indicate non-independent living skills, scores between -1 SD and the mean (i.e., 85 to 99) indicate semi-independent living skills and scores equal to or greater than the mean (i.e., 100 to 115) indicate independent living skills. Internal consistency of the ILS ranges from .72 to .87 for the sub-scale scores, is .86 to .92 for the factor scores, and is .88 for the Full Scale score. Test-retest reliability of the ILS ranges from .81 to .92 for the subscale scores, is .90 and .94 for the factor scores, and is .91 for the Full Scale score. Inter-rater reliability of the ILS ranges from .95 to .99 for the subscale scores, is .98 and .99 for the factor scores, and is .99 for the Full Scale score (Loeb, 1996).

Autistic Symptomatology

Autistic symptomatology was measured using the Autism Diagnostic Observation Schedule (ADOS; Lord et al. 2000). The ADOS is a semi-structured observational measure of autistic behavior administered directly to the participant by a trained researcher or clinician. The assessment lasts approximately 30-60 minutes, during which the researcher or clinician engages the individual in a number of activities designed to elicit behaviors related to the diagnosis of autism. Participants receive one of four modules assigned on the basis of the participant's expressive language age. Items contributing to three domains – Communication, Reciprocal Social Interaction, and Stereotyped Behaviors and Restricted Interests – are rated by the clinician according to standardized criteria. A subset of algorithm items from the Communication and Reciprocal Social Interaction domains are used to generate a Communication + Social Interaction Total score (hereafter known as the “total score”). The psychologist (AAL) who administered the ADOS was certified in ADOS administration according to the standards established by the University of Michigan where the scale was developed, was trained to consensus reliability of 80% and above on all items, and followed the standardized protocol for rating items contained in the manual. Ninety-five participants (62 FXS, 33 controls) were administered Module 4, four participants (3 FXS, 1 control) were administered Module 3, four participants (3 FXS, 1 control) were administered Module 2, and two participants (2 FXS, 0 controls) were administered Module 1. The vast majority of participants in each group were therefore administered Module 4, as would be expected for individuals aged 15 to 25 years.

Statistical Analyses

We first computed the percentage of participants in each group who obtained standard scores on the ILS within the non-independent, semi-independent, or independent range of living skills. We then compared the two groups on the scores obtained on the subscales, factors and total score of the ILS. Given that 33 (47.1%) participants with FXS and 12 (34.3%) controls obtained a Full Scale standard score of 55 on the ILS (i.e., on the floor of the measure), we used raw scores in the analyses. To examine the relationship between autistic symptomatology and independent living skills, we conducted a correlation analysis of the data by computing Pearson correlations between the total score obtained on the ADOS and the raw scores obtained on the ILS. To control for IQ in these analyses, we then conducted a second correlation analysis in which IQ was included as a control variable. To compare correlation coefficients between the groups, we used Fisher's r-to-z transformation (http://vassarstats.net/rdiff.html). Alpha level was set at p = .05, two tailed.

Results

Independent Living Skills

Fifty-three (75.7%) participants with FXS (35 male, 18 female) and 29 (82.9%) controls (14 male, 15 female) received scores in the non-independent range on the ILS. Eight (11.4%) participants with FXS (0 male, 8 female) and 4 (11.4%) controls (2 male, 2 female) received scores in the semi-independent range on the ILS. Finally, 9 (12.9%) participants with FXS (0 male, 9 female) and 2 (5.7%) controls (0 male, 2 female) received scores in the independent range on the ILS. There were no significant differences between the groups in terms of living status on the ILS (X2(2) = 1.29, p = 0.53).

Table 2 shows the mean raw scores obtained on the subscales, factors and total score of the ILS for the FXS and control groups. Statistical analyses showed that were no significant differences between the groups on these scales (all p's > 0.05) indicating that the profile of scores obtained on the ILS was strikingly similar between the groups. As would be expected for an X-linked genetic disorder, males with FXS received significantly lower scores on the ILS than females with FXS on all subscales, factors, and on the total score (all p's < 0.001).

Table 2.

Mean raw scores obtained on the ILS subscales, factors and total score for each group.

ILS Subscale/Factor FXS (N=70) Controls (N=35) t p
Subscale
 Memory/Orientation 11.49 (4.23) 12.63 (3.22) 1.41 0.16
 Managing Money 13.60 (10.41) 12.91 (8.71) 0.34 0.74
 Managing Home and Transportation 17.26 (8.13) 18.14 (7.43) 0.54 0.59
 Health and Safety 22.56 (10.02) 23.40 (9.17) 0.42 0.68
 Social Adjustment 15.30 (3.50) 16.29 (2.07) 1.54 0.13
Factor
 Problem Solving 36.11 (17.08) 36.94 (16.67) 0.24 0.81
 Performance/Information 20.54 (11.70) 20.89 (9.59) 0.15 0.88
Total score 80.2 (33.43) 83.37 (27.43) 0.49 0.63
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Autistic Symptomatology

Sixteen (22.9%) participants with FXS (12 male, 4 female) and 7 (20.0%) controls (4 male, 3 female) received a classification of autism on the ADOS. Thirteen (18.6%) participants with FXS (11 male, 2 female) and 1 (2.9%) control (female) received a classification of autism spectrum. Finally, 41 (58.6%) participants with FXS (12 male, 29 female) and 27 (77.1%) controls (12 male, 15 female) received a classification of none. As would be expected for an X-linked genetic disorder, males with FXS received significantly higher total scores on the ADOS (M = 9.24, SD = 3.94) than females with FXS (M = 4.06, SD = 3.76) (t(66) = 5.54, p < 0.001).

Association between Autistic Symptomatology and Independent Living Skills

To examine whether degree of autistic symptomatology was associated with degree of independent living skills in each group, we conducted correlation analyses of the total scores obtained on the ADOS with the raw scores obtained on the ILS. We also conducted a second analysis in which IQ was included as a control variable in the analyses, to partial out the confounding effects of IQ. Tables 3 and 4 show the results.

Table 3.

Correlations obtained between the ADOS total score and ILS subscale, factor and total raw scores in each group. The difference between the two correlations was assessed using Fisher's r-to-z transformation.

ILS Subscale/Factor FXS (N=70) Controls (N=35) z p
Subscale
 Memory/Orientation -.453** -.250 1.08 .140
 Managing Money -.712** -.285 2.78 .003
 Managing a Home and Transportation -.674** -.410* 1.78 .075
 Health and Safety -.676** -.394* 1.89 .059
 Social Adjustment -.499** -.256 1.33 .184
Factor
 Problem Solving -.719** -.356* 2.48 .013
 Performance/Information -.644** -.326 1.99 .047
Total score -.705** -.382* 2.21 .027
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*

p < .05;

**

p < .01

Table 4.

Partial correlations obtained between the ADOS total score and ILS subscale, factor and total raw scores in each group, controlling for IQ. The difference between the two correlations was assessed using Fisher's r-to-z transformation.

ILS Subscale/Factor FXS (N=70) Controls (N=35) z p
Subscale
 Memory/Orientation -.149 -.067 .53 .596
 Managing Money -.548** -.011 2.81 .005
 Managing a Home and Transportation -.463** -.234 1.22 .111
 Health and Safety -.465** -.203 1.39 .165
 Social Adjustment -.273* -.113 .78 .435
Factor
 Problem Solving -.555** -.145 2.23 .026
 Performance/Information -.396** -.066 1.64 .101
Total score -.527** -.173 1.91 .056
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*

p < .05;

**

p < .01

Table 3 shows that the correlations between the total score on the ADOS and the scores on the ILS were all highly significant for individuals with FXS, ranging from -0.453 to -0.712 (all p's < 0.001). The correlations between the total score on the ADOS and scores on the ILS were substantially smaller in the controls, ranging from -0.250 to -0.410. Comparison of the correlation coefficients between the two groups using Fisher's r-to-z transformation indicated that the correlation coefficients were significantly different on the Managing Money (p = 0.003) subscale, on the Problem Solving (p = 0.013) and Performance/Information (p = 0.047) factors, and on the total score (p = 0.027). These data indicate that the magnitude of the association between degree of autistic symptomatology and degree of independent living skills was significantly greater in individuals with FXS than in matched controls.

To examine whether this relationship was also apparent when IQ was controlled, we included IQ as a control variable in the correlation analyses. Table 4 shows that in individuals with FXS, the partial correlations between the ADOS total score and the ILS total raw score, when controlling for IQ, were all statistically significant (with the exception of the memory/orientation subscale), ranging from -0.273 to -0.548 (all p's < 0.05). Indeed, in the control group, the partial correlations between the ILS total raw score and the ADOS total score, when controlling for IQ, were all non-significant (Table 4). Comparison of the correlation coefficients between the two groups using Fisher's r-to-z transformation indicated that the correlation coefficients were significantly different on the Managing Money (p = 0.005) subscale, as well as on the Problem Solving (p = 0.026) factor. These data indicate that the magnitude of the association between autistic symptomatology and independent living skills was significantly greater in individuals with FXS than in matched controls, even when IQ was controlled in the analyses.

Discussion

We examined the association between autistic symptomatology and level of competence in independent living skills in a group of older adolescents and young adults with FXS using the ADOS and the ILS, two direct measures of these respective constructs. Correlation analyses indicated that participants with FXS who had greater levels of autistic symptomatology were more dependent on the support of others than individuals with fewer autistic symptoms. In fact, the total score on the ADOS was significantly negatively associated with degree of independent living skills, even when controlling for IQ in participants with FXS. These results broadly support previous research indicating that individuals who meet diagnostic criteria for autism, demonstrate poorer functional and independent living skills than those who do not (Bailey et al. 2009; Hartley et al. 2011; Howlin et al. 2004).

The current study extends these findings in several ways. First, rather than simply coding whether or not a participant had previously received either a diagnosis or treatment for autism or ASD, we examined the association between degree of autistic symptomatology and degree of independent living skills in this population using directly administered assessment measures. Second, the current study compared individuals with FXS to a control group of individuals who were matched for sex, age, IQ, and autistic symptomatology indicating that degree of autistic symptomatology was more strongly related to independent living skills for individuals with FXS than controls (i.e., the relationship was syndrome-specific). Finally, participants in the current study were asked to both explain and demonstrate skills requisite for independent living. Previous studies assessing the functional and independent living skills of individuals with FXS have relied on parental report of living skills. Generally speaking, direct methods of measuring behavior are thought to be superior to indirect methods because they suffer from fewer limitations related to recall and response bias, and issues with subjectivity, reliability, and validity.

When we examined scores on the ILS, we found that 100% of males with FXS and 51% of females with FXS obtained scores in the non-independent range of functioning. 23% of females with FXS obtained scores in the semi-independent range, and the remaining 26% of females with FXS obtained scores in the independent range. These data indicate that males with FXS were particularly dependent on the support of others. Interestingly, when we compared individuals with FXS to the controls who were matched on age, IQ and degree of autistic symptomatology, we found that individuals with FXS were, in fact, no more impaired in terms of independent living skills that their peers who did not have FXS. These data underline the importance of including a matched control group of individuals in analyses of syndrome groups.

As expected, males with FXS obtained significantly lower scores on the ILS and significantly higher total scores on the ADOS compared to females with FXS. It is important to point out that males with FXS also obtained significantly lower IQ scores than females with FXS, as expected for an X-linked genetic disorder, thus, IQ is a confounding variable. Therefore, the appropriate way to examine the association of autistic symptomatology and independent living skills in this population is to conduct analyses on the group as a whole (i.e., males and females combined), and to partial out the effects of IQ. Had we conducted separate analyses of males and females with FXS, we would also have encountered range restriction issues.

To our knowledge, this is the first study to employ the Independent Living Scales as a measure of independent living skills in individuals with FXS. Revheim and Medalia (2004) evaluated this tool as a measure of functional outcome for individuals diagnosed with schizophrenia. In their study, the ILS Problem Solving factor was significantly predictive of living status (discriminating three levels of need for supervision: “maximum”, i.e., 24-hour hospitalization; “moderate”, i.e., daily contact with care staff; and “minimum” supervision, i.e., intermittent contact with case managers, presence of roommates, or living alone) in 87 inpatients and 75 outpatients with a diagnosis of schizoaffective disorder or schizophrenia. Although most participants in the present study were currently living at home with parents or caregivers, our study conclusion is somewhat hampered by our lack of information about the level of supervision in place in our participants' current living environments. Future research could address this limitation by assessing the ability of the ILS to predict level of support, as well as comparing scores on the ILS to other widely used measures of independence, such as the Activities of Daily Living (Katz 1983).

Of note is that much research has described the autistic symptomatology displayed by individuals with FXS on a categorical basis (e.g., “FXS + autism”, “FXS only”), rather than as behavior that occurs on a continuum. Individuals with “FXS + autism” have been reported to have lower levels of IQ, and therefore the distinction between those “with autism” and those “without autism” may be confounded by IQ. This was also the case in the present study, suggesting that the addition of an autism diagnosis in this population may no longer be useful, or could be considered a potentially paradoxical concept (Hall et al. 2010). Indeed, given that FXS is an established genetic disorder whereas ASD is a disorder diagnosed on the basis of behavioral symptoms only, researchers and clinicians may be making a “category mistake” by conjoining the two disorders. Specific differences in symptomatology between individuals diagnosed with FXS and individuals diagnosed with idiopathic autism have also been identified, particularly in the reciprocal social interaction domain (Hall et al., 2010; Moss et al., 2013).

Overall, the current study suggests that adults with FXS exhibit a similar level of competence in independent living skills as a matched group of individuals without FXS, but that competency in independent living skills in adulthood may be significantly impacted by the presence of autistic symptomatology for individuals with FXS. While these factors are likely critical for individuals with intellectual disabilities in general, regardless of specific etiology, these relationships may be particularly important for individuals with FXS, as they were more strongly associated to independent living skills in this group compared to controls. It is possible that symptoms of severe social anxiety – a hallmark behavioral feature of FXS that may be correlated with autistic symptomatology –may be partly responsible for the poorer outcomes observed in those with FXS. Future research will need to investigate the possibility that symptoms of social anxiety, in combination with autistic symptoms, may interfere with the acquisition of independent living skills in this population.

Research into the determinants and developmental course of fragile X syndrome (FXS) has made remarkable progress over the last 25 years, yet treatments to ameliorate the symptoms of FXS have been less forthcoming. While there is optimism in the field that the pace of intervention research is quickening, there has been a bias toward psychopharmacological approaches to treatment. A closer look at the data from those investigations reveals a paucity of evidence that medications can improve intellectual and adaptive functioning in FXS, or decrease associated behavioral and/or emotional issues (Hall, 2009). Work in other related disorders (e.g., autism) has shown that dramatic improvements in intellectual and adaptive functioning, as well as behavioral and emotional problems, can occur if intensive behavioral treatment is begun early in the child's life. It is hoped that future research efforts will evaluate these intensive early intervention strategies in children with FXS, perhaps in combination with pharmacological approaches. A recent large-scale longitudinal study of adaptive behavior profiles shown by individuals with FXS over childhood to adulthood indicated that the most meaningful improvements in daily living skills occurred after 14 years of age (Klaiman et al., 2014). These data indicate that the developmental period from childhood to early adolescence is critical and that intervention strategies that address autistic symptomatology (and underlying symptoms of social anxiety) in FXS during this period are sorely needed. It seems likely that intensive interventions targeted to autistic symptoms in FXS may greatly increase the likelihood of individuals with FXS achieving the highest level of independence possible in later life.

Acknowledgments

This study was supported by grant numbers MH50047 (PI Allan Reiss) and K08MH081998 (PI Scott Hall) from the National Institute of Mental Health, a gift from the Canel Family, and the Fonds de Recherche Société et Culture Québec (Postdoctoral grant to Eve-Marie Quintin).

Contributor Information

Kristin M. Hustyi, Email: khustyi@stanford.edu.

Eve-Marie Quintin, Email: eve-marie.quintin@mcgill.ca.

Lindsay C. Chromik, Email: lchromik@stanford.edu.

Amy A. Lightbody, Email: aal@stanford.edu.

Allan L. Reiss, Email: areiss1@stanford.edu.

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