Exploring the Prevalence and Predictors of Depression in Young Adults with Autism Spectrum Disorders

Background: Although co-occurring psychiatric disorders are recognised to affect up to 70% of individuals with ASD, there have been few large-scale epidemiological investigations of adult comorbidity. With regard to symptoms of depression in ASD, previous studies have revealed widely varying prevalence estimates (from 0.9%-77%), and no studies to date have explored the longitudinal predictors of these difficulties.

Objectives: The current study aimed to explore the prevalence and predictors of depressive symptoms within a longitudinal, epidemiologically-derived cohort.

Methods:   A subsample of 96 young adults (aged 21-24 years) from the population-derived Special Needs and Autism Project (SNAP) were assessed for depression using a standardised clinical interview (the Young Adult Psychiatric Assessment: YAPA) and the Beck Depression Inventory (BDI-II). Parent-report measures of young adult depression were also available for 104 families. Analyses assessed the prevalence of depression in the full sample and in those with IQ above and below 70. Predictors of depression were assessed cross-sectionally and longitudinally (at age 1, 16 and 23 years), including IQ, ASD severity, internalising symptoms, stressful life events and demographic / family characteristics. Associations between quality of life and depressive symptoms were also explored. 

Results: 18.9% of young adults with ASD reached criteria for ‘any depressive disorder’, with significantly higher rates in those with IQ above compared to below 70. The prevalence of depression at age 23 years was significantly higher than the rates observed earlier in the study, at age 12 (1.4%) and age 16 (5.5%). Depression at age 23 was predicted significantly by self-reported ASD severity (OR: 1.06 CI 1.00-1.12; p<0.05) at the same age and the number of significant life-events experienced (OR: 1.54 CI 1.14-2.07; p<0.01). Young adult depression was also predicted, longitudinally, by the individual’s level of adaptive functioning at age 12 (OR: 1.07 CI 0.99-1.15, p=0.05). No family characteristics or demographic factors emerged as significant predictors of depression. Additional associations were observed between symptoms of depression, anxiety across development and reduced quality of life at age 23 years.

Conclusions: Rates of depression were higher in young adults with ASD compared to the general population, with an emergence of symptoms in late adolescence and early adulthood. Certain individuals, including those with higher IQ, higher perceived ASD severity and a history of emotional difficulties may be more susceptible to depressive symptoms. Co-occurring depressive symptoms constitute key targets for prevention and treatment in young adults with ASD.