Pre-adult onset of major depressive disorder (MDD) may predict a more severe phenotype of depression. As data from naturalistic psychiatric specialty care settings are scarce, we examined phenotypic differences between pre-adult and adult onset MDD in a large sample of consecutive out-patients.

Altogether, 1552 out-patients, mean age 39.2±11.6 years, were diagnosed with current MDD on the Mini-International Neuropsychiatric Interview Plus diagnostic interview as part of the usual diagnostic procedure. A total of 1105 patients (71.2%) had complete data on all variables of interest. Pre-adult onset of MDD was defined as having experienced the signs and symptoms of a first major depressive episode before the age of 18 years. Patients were stratified according to the age at interview (20–40/40–65 years). Correlates of pre-adult onset were analysed using logistic regression models adjusted for age, age squared and gender.

Univariate analyses showed that pre-adult onset of MDD had a distinct set of demographic (e.g. less frequently living alone) and clinical correlates (more co-morbid DSM-IV – Text Revision diagnoses, more social phobia, more suicidality). In the multivariate model, we found an independent association only for a history of suicide attempts [odds ratio (OR) 3.15, 95% confidence intervals (CI) 1.97–5.05] and current suicidal thoughts (OR 1.81, 95% CI 1.26–2.60) in patients with pre-adult versus adult onset MDD.

Pre-adult onset of MDD is associated with more suicidality than adult onset MDD. Age of onset of depression is an easy to ascertain characteristic that may help clinicians in weighing suicide risk.