Internalizing Symptoms in Adults with ASD: Relation to ASD Symptomatology

Background:  Studies of internalizing symptoms in autism spectrum disorder (ASD) estimate that approximately 40-45% of individuals with ASD have significant levels of anxiety and depression (Sterling et al., 2007; White et al., 2009). To assess internalizing symptoms, measures used in the general population or those being used with individuals with intellectual disability (ID) are being adapted or considered for use in ASD. However, given overlap of symptoms, it can be difficult to differentiate ASD and internalizing symptoms, raising the possibility of diagnostic overshadowing and challenging differential diagnosis. The wide range of functioning in ASD complicates measurement and screening of internalizing symptoms. 

Objectives:  The purpose of this study was to examine caregiver reported internalizing symptoms and how these symptoms relate to severity of ASD.  This study assessed a variety of internalizing problems in adults with ASD across a wide range of intellectual functioning and ASD symptom severity. 

Methods:  Caregivers completed surveys about adults with ASD as part of a study on the long-term outcome and needs of individuals with ASD in mid-adulthood served as children by the University of North Carolina TEACCH Autism Program. Thus far, 81 caregivers have completed surveys. Adults with ASD had an average age of 33 years (range 20-64 years). The Social Responsiveness Scale, Second Edition (SRS-2; Constantino & Gruber, 2012) Adult (Relative/Other Report) and Waisman Activities of Daily Living Scale (W-ADL; Maenner et al., 2013) were completed in addition to a screening instrument for internalizing symptoms developed for use among individuals with ID, the Anxiety, Depression, and Mood Scale (ADAMS; Esbensen et al., 2003).

Results:  The SRS-2 total score was significantly positively correlated with all factors of the ADAMS although the strength of the correlation varied across factors. General Anxiety was significantly positively correlated with SRS-2 total, r = .35, p = .002, as was Depressed Mood, r = .23, p < .04, Social Avoidance, r = .62, p < .001, Compulsive Behavior, r = .49, p < .001, and Hyper/Manic Behavior, r = .51, p < .001. Better adaptive skills were significantly related to fewer internalizing symptoms and fewer ASD symptoms. When adaptive skills were controlled for, SRS-2 total and ADAMS factors of Social Avoidance, Compulsive Behavior, and Hyper/Manic Behavior remained significant; Generalized Anxiety and Depression were no longer related to SRS-2 total.

Conclusions:  Generally, internalizing symptoms on the ADAMS were related to increased ASD symptoms and fewer adaptive skills. However, these results do not necessarily suggest that those with more ASD symptomatology are at higher risk for comorbidity. Instead, some internalizing factors may be measuring symptoms of ASD. For instance, ASD symptoms were most highly correlated with Social Avoidance and Compulsive Behavior, which overlap with symptoms of ASD. However, Generalized Anxiety and Depression scores were weakly correlated with ASD symptoms and may be more indicative of comorbidity on this screener. These results suggest that increased focus on appropriate screening and measurement of comorbidity in adults with ASD deserves significant attention as it has important implications for treatment, community service needs, and quality of life.