The incidence of depressive symptoms among adolescents has been increasing in the last years and several risk factors have been associated with depression which has become a major public health issue.

Assess the prevalence and determinants of depression in a Portuguese sample of adolescents.

A cross-sectional study was designed with a sample of 447 adolescents aged 12 to 19 years old, attending a public school in S tao, Portugal. A self-administered questionnaire with questions about socio-economic status, risk behaviours and sleep disorders was answered by adolescents. Depressive symptoms were assessed by the Portuguese validated version of the Beck Depression Inventory, and the cut-off point for depression was 13 points. We considered the following global scores: 0-13:minimal depression; 14-19:mild depression; 20-28:moderate depression; and 29-63:severe depression. Prevalence was expressed in proportions and compared by the Chi-square test.

The prevalence of depressive symptoms was 13.2%. According to the severity of depressive symptomatology, the prevalence of minimum, slight and moderate depressive symptoms was 57.4%, 5.4% and 2.3%, respectively. Depression was associated with insomnia (yes, OR=7.9 95%CI=3.1-19.9), residence area (urban, OR=1.4 95%CI=1.1-2.1), father’s educational level (<9yrs, OR=3.4 95%CI=1.1-10.2), alcohol consumption (OR=1.6 95%CI=1.1-2.2), coffee consumption (OR=1.4 95%CI=1.0-1.9) and smoking habits (OR=1.5 95%CI=1.2-1.8).

Adolescents who develop depression are also likely to develop insomnia. Depressive symptoms are associated with sociodemographic variables and addictive habits. Mental health promotion should be considered in school programmes in order to decrease the risk of depression and associated diseases.