The present study aims to develop a new predictive index to predict future depression of adolescents by using factors including individual, interpersonal and environmental. The index can be used to predict likelihood of students who are non-probable depression cases convert into probable depression cases. In addition, the investigators also test the factors of depression remission. It can hence be used in school setting to identify high-risk students, and provide them with secondary interventions that are designed by considering modifiable significant variables identified in this unique, large-scale, longitudinal study.

A 12-month longitudinal study will be conducted in secondary school settings.

The investigators will investigate incidence of probable depression (i.e., from non-depression, CESD<16, at baseline to probable depression, CESD≥16, at month 12) and remission of probable depression.

The investigators will investigate factors that can prospectively predict new cases/remission of probable depression, including both well-documented risk/protective factors and some under-examined but potentially important local factors (e.g. school/academic stress, psychological resilience). The relative importance of the risk/protective factors at different socio-ecological levels will be compared and their combined effect will be identified.

Based on the selected factors, the investigators will derive a new prediction index called the Adolescent Depression Prediction Index (ADPI) in a model building sample and test its performance in predicting incidence of depression in a validation sample among secondary school students in Hong Kong.

Inclusion Criteria:

• Secondary 1 (seventh year of formal education) to Secondary 4 Chinese students, who are studying local mainstream schools in Hong Kong.
• Able to read Chinese and speak either Cantonese or Mandarin.

Exclusion Criteria:

• Eligible students whose parents refuse to give consent to take part in the study.

Out of the 18 districts in Hong Kong, nine randomly selected districts will select randomly two schools and while the rest nine will randomly select one school. Replacements of schools will be made upon refusals. Within the selected schools, all Secondary 1-4 students will be invited to join the study. Students will be asked to fill in baseline questionnaires in the absence of teachers in classroom settings.