Depression in children and adolescents is a complex and multi-causal disorder.

The vulnerability factors for suffering from depression focus on biological characteristics (family history of mental disorder, age, sex, chronic medical illness, etc.) and temperamental characteristics (negative affectivity, ruminative thinking, difficulties in relationships with peers, etc.), on the child's interaction with the environment (stressful life events, family conflicts, abuse, mistreatment, school problems, bullying, humiliation, etc.) and on the characteristics of the child (culture, educational style, economic precariousness, etc.).

Some of the factors that can reduce the likelihood of depression when there are vulnerability factors are: having social skills and an adequate circle of friends, positive affectivity, having a close and trusting relationship with family members, doing some leisure or sports activity, etc.

It should be noted that a single factor cannot explain the development of depression, reduce the likelihood of it developing or be sufficient to prevent it by controlling it.