Childhood trauma as a mediator between autistic traits and depression: evidence from the ALSPAC birth cohort

BackgroundAutism and autistic traits have been associated with greater risk of childhood trauma and adulthood psychopathology. However, the role that childhood trauma plays in the association between autism, autistic traits and depression in adulthood is poorly understood. MethodsWe used a UK-based birth cohort with phenotype and genotype data on autism, autistic traits, childhood trauma and depression in up to 9,659 individuals prospectively followed up from birth until age 28 years. Using mixed-effects growth-curve models, we assessed trajectories of depression symptoms over time according to the presence or absence of autism/ autistic traits and explored whether these differed by trauma exposure. We further investigated the association between autism/ autistic traits and depression in adulthood using confounder-adjusted logistic regression models and undertook mediation analyses to investigate the relationship with childhood trauma. ResultsAll autism variables demonstrated increased depressive symptom trajectories between ages 10-28 years. Social communication difficulties (SCDs) were the most strongly associated with a depression diagnosis in adulthood (age 24 OR= 2.15; 95%CIs: 1.22-3.76). Trauma and autistic traits combined to further increase depression symptom scores. Mediation analyses provided evidence for direct pathways between autistic traits and increased risk of depression alongside indirect pathways through increased risk of trauma. ConclusionsAutism/ autistic traits increase the odds of experiencing childhood trauma and of being diagnosed with depression at age 18 and 24. Depressive symptom trajectories emergent in childhood persist into adulthood. The combined effect of SCDs and childhood trauma is greater than the individual exposures, suggesting worse depression symptomatology following trauma in individuals with SCDs. Lay abstractAutism and autistic traits are linked to higher chances of experiencing traumatic events in childhood and having mental health problems as an adult. However, we dont understand how childhood trauma influences the link between autistic traits and depression in adulthood. Using data from a large birth cohort study in the UK, we tracked up to 9,659 people from birth until age 28 years. We looked at the links between autism, autistic traits, childhood trauma, and depression. We found that all features related to autism were associated with more symptoms of depression between the ages of 10 and 28. Among these, difficulties in social communication were the most strongly connected to depression when they reached adulthood, more than doubling the risk. We discovered that when childhood difficulties and autistic traits came together, the risk of experiencing depression symptoms increased even more. We showed that autistic traits raised the chances of depression both directly and indirectly, by increasing the chance of experiencing childhood trauma. Taken together, our research shows that autism and autistic traits increase the likelihood of experiencing childhood trauma and being diagnosed with depression at ages 18 and 24. Signs of depression that appear in childhood tend to persist into adulthood. The combination of social communication difficulties and childhood trauma has a stronger impact on depression symptoms, indicating that people with these traits may experience more severe depression after facing traumatic events.