During a study published in JAMA Network Open, researchers found associations between autism spectrum disorders (ASD) and depression in young adults — particularly patients without intellectual disabilities. Researchers sought to examine this association to determine whether depression had a familial basis in this population and whether the association differ with co-occurring intellectual disability.
The population-based cohort study included a nested full and half-sibling comparison and examined 223,842 individuals, with the oldest participants reaching age 27. Of these individuals, 4073 had a diagnosis of ASD. The participants diagnosed with ASD were further categorized into those with intellectual disabilities and those without.
The study found that between the ages of 18 and 27, 19.8% of individuals diagnosed with ASD had been diagnosed with depression, compared with 6% of the population without ASD (adjusted relative risk [RR] 3.64; 95%, CI 3.41-3.88). When taking into consideration the presence of intellectual disability, 24.1% of individuals without intellectual disability had been diagnosed as being depressed (adjusted RR 4.28; 95% CI, 4.00-4.58), compared with 9.1% among individuals without ASD (adjusted RR 1.81; 95% CI, 1.51-2.17). The full (adjusted RR 1.37; 95% CI, 1.23-1.53) and half-siblings (adjusted RR 1.42; 95% CI, 1.23-1.64) without ASD also had a higher risk for depression. The findings are in line with studies that have found similar results among patients with ASD, but this study is the first to examine the data against comparison groups. The risk for individuals with ASD to receive a depression diagnoses was more than double that of full siblings who do not have autism (adjusted odds ratio 2.50; 95% CI,1.91-3.27)
Findings from the study seem to suggest that given the increased presence of depression among siblings of ASD individuals, an increased genetic vulnerability seems evident, but siblings of children with ASD may be prone to psychiatric illness because of other mechanisms. Furthermore, the lack of intellectual disabilities among those with ASD and depression could suggest a higher cognitive functioning that may lead to increased awareness in regard to the challenges of being different.
Limitations of the study include lack of data regarding undiagnosed depression and lack of data on the severity of depressive symptoms. The means of data collection could also lead to misclassification of the diagnoses.
Researchers conclude that data suggests common environmental pathways between ASD and depression and emphasize the need for further research to understand the associations present. A fuller understanding of the associations between ASD and depression could help in the development of new preventive strategies and interventions.
Rai D, Heuvelman H, Dalman C, et al. Association between autism spectrum disorders with or without intellectual disability and depression in young adulthood [published online August 31, 2018]. JAMA Netw Open. doi:10.1001/jamanetworkopen.2018.1465