Author	L.P.M.M. Wijlaars
Author	I. Petersen
Author	I. Nazareth
Abstract	Background: Although depression can affect anyone at any time, the first year after the birth of a child appears to be a time when both parents are more likely to experience depression. Research has mainly focussed on maternal perinatal or early depression which has an estimated incidence of 10-15%. Less is known about early paternal depression or early comorbid depression, where both parents experience depression. Methods: I conduct a systematic review on the prevalence of early comorbid parental depression and associated childhood outcomes. Next, I explore adolescent depression recording in UK primary care, and trends over time. Finally, I use structural equation modelling to provide a quantitative analysis of the association between early comorbid parental depression and adolescent outcomes, focussing on the effects of recurrent parental depression and internalizing behaviours in childhood. I examine depression and its intergenerational transmission using data from a large UK primary care database, The Health Improvement Network (THIN). Results: Prevalence of early comorbid depression in parents ranged from 0 to 20%. However, it was not feasible to perform a meta-analysis due to measurement variation and study quality. I identified only two studies assessing child outcomes. Diagnoses of adolescent depression and antidepressant prescribing have increased in recent years despite a temporary drop in 2002-2005. Symptom recording increased steadily between 1995-2009. I did not find evidence for an association between early comorbid parental depression and adolescent depression (OR: 2.02, 95% CI: 0.42-9.67). Early maternal depression does increase the risk of adolescent depression. The effect is mainly indirect, mediated by recurrent parental depression (OR: 1.54, 95% CI: 1.26-1.87), as opposed to direct (OR: 1.06, 95% CI: 0.69-1.63). Childhood internalizing behaviour might be an early indicator of depression risk. Conclusion: Early parental depression increases the risk of adolescent depression, but the effect is strongly mediated by recurrent parental depression.