Background: The authors examined an additive model for the association of life events and age with onset of major depressive disorder (MDD) and whether the combination of life events and age posed greater risk than the sum of their independent effects. Methods: Data were used from a prospective cohort study of 10,045 general practice attendees (PredictD). We included those without MDD at baseline (N = 8293). We examined age divided into tertiles and into 10 year groups. Life events were assessed at baseline using the List of Threatening Life Experiences Questionnaire and categorized according to type. Main outcome measure was onset of DSM-IV MDD at 6 or 12 months of follow-up. The authors calculated Relative Excess Risks due to Interaction (RERI). Results: 6910 persons (83.3%) had a complete follow-up, of whom 589 (8.5%) had an onset of MDD (166 younger, 254 middle aged and 169 older). The combined effect of personal problems (RERI = 1.30; 95% CI 0.29 to 2.32), events in family or friends (RERI = 1.23; 95% CI 0.28 to 2.19), or problems with law (RERI = 1.57; 95% CI 0.33 to 2.82) and middle age was larger than the sum of individual effects. Limitations: Lower response to recruitment in the UK and the Netherlands. Conclusions: Recent life events carry the largest risk of onset of MDD in mid-life. Understanding the different vulnerability to life events according to age may help to indicate groups at a particular risk and assist in preventive strategies.
- Major depression