To estimate lifetime risk and ages of onset of mental disorders in the adult general population of Belgium.

For the World Mental Health Surveys of the World Health Organization, a representative random sample of non-institutionalized inhabitants from Belgium aged 18 or older (n=2419) were interviewed. The interview took place by means of the CIDI 3.0. Lifetime prevalence, projected lifetime risk, and age of onset were assessed.

Compared to lifetime prevalence rates, projected lifetime risk remains fairly stable for anxiety disorders, but is increased for mood and alcohol disorders: The lifetime risk for any mental disorder was 37.1%: 22.8% for mood disorders, 15.7% for anxiety disorders, and 10.8% for alcohol disorders. Prevalence estimates of mood and alcohol disorders were significantly higher in the cohorts between 18 and 34 years. Age of onset-distribution are presented for mood, alcohol and anxiety disorders.

This is the first study that assessed projected lifetime risks and ages of onset in the Belgian general population. A significant difference is noted between lifetime prevalence rates and projected lifetime risk. Median age of onset varies from disorder to disorder and younger cohorts had higher likelihood for developing mental disorders.