Autism may increase the risk for depression in young adulthood, a Swedish study found.
In a large group of individuals with autism, nearly 20% were diagnosed with major depressive disorder by the age of 27 versus only 6% of the general population (adjusted RR 3.64, 95% CI 3.41-3.88), reported Dheeraj Rai, MRCPsych, PhD, of the University of Bristol in the U.K., and colleagues.
The researchers also found that young adults with autism without intellectual disability were more likely to have depression compared with those with autism with intellectual disability (aRR 4.28, 95% CI 4.00-4.58 versus aRR 1.81, 95% CI 1.51-2.17).
As shown in the study in JAMA Network Open, individuals with autism overall -- i.e., those with and without intellectual disability -- had a 2.5-fold higher risk for depression when compared with their non-autistic full siblings (adjusted OR 2.50, 95% CI 1.91-3.27). However, siblings were not totally free of a higher depression risk either, and this extended to both non-autistic full and half-siblings of those with autism. Specifically, full siblings had a 37% (95% CI 1.23-1.53) higher risk, while half-siblings had a 42% (95% CI 1.23-1.64) higher risk for depression compared with people in the general population.
The team said the findings were not particularly surprising, since previous studies have found a similarly high risk of depression among adults with autism. And while the clinically relevant finding in this study was the difference in risk among those with and without intellectual disability, this may suggest "that those with greater cognitive ability and thus insights into being different may be more prone to depression."
"While this finding may suggest an important distinction between these [autism spectrum disorders, ASD] subgroups, the weaker estimates for depression in people with ASD who have intellectual disability may also be an artifact of diagnostic overshadowing -- which refers to clinicians missing treatable comorbidities in people with intellectual disability and instead attributing them to be a core feature of their intellectual disability," the group explained. In addition, those with intellectual disability may not be able to verbally express their depressive symptoms leading to a formal diagnosis.
The finding regarding siblings' elevated depression risk may suggest a "common genetic vulnerability," but it is actually more likely that the underlying mechanism is due to environmental factors, the researchers suggested. "For example, [siblings] may receive less parental attention because of their autistic sibling with greater needs or may experience other stressors or discord in the household, or they may be more likely to have closer monitoring because their sibling has a diagnosis of autism."
The analysis included 223,842 Swedish individuals from the Stockholm Youth Cohort. A total of 4,073 of these participants received a diagnosis of ASD between birth and the age of 17 as identified through medical records, with nearly 3,000 free of intellectual disability. These individuals were compared with approximately 220,000 young people without ASD, including full and half siblings. Depression diagnoses were also obtained through records.
Ultimately, Rai and co-authors called for additional research on the topic, but also concluded that these findings suggest that an autism diagnosis should prompt clinicians to provide relevant tools for the patients and families in the form of social services, education, and emotional support.
The study was funded by grants from the Baily Thomas Charitable Foundation and the Swedish Research Council for Health, Working Life, and Welfare. Additional support was provided by the National Institute for Health Research Biomedical Research Centre at the University Hospitals Bristol National Health Service Foundation Trust and the University of Bristol.
Rai reported receiving grants from The Baily Thomas Charitable Foundation, the National Institute for Health Research, and the Swedish Research Council for Health, Working Life and Welfare during the conduct of the study; one co-author also noted being funded by an Elizabeth Blackwell Institute for Health Research Early Career Fellowship.
JAMA Network Open
Source Reference: Rai D, et al "Association between autism spectrum disorders with or without intellectual disability and depression in young adulthood" JAMA Network Open 2018; DOI: 10.1001/jamanetworkopen.2018.1465.