Biologic reasons: A reason can be the release from the Neurotransmitters (messengers in the brain) Noradrenaline, Serotonine, Dopamine. But no one knows if it's the shortage or the aburdance that makes Depressions. It can also be that the depressions affect the release of the Neurotransmitters. Another theory is that there's a genetic Factor because examinations showed that identical twins both have severe depressions.

Psychologic reasons: There are a lot of factors like: Bullying ,stress at work or in the family, chronic pain, no friends, the loss of someone, abuse or traumas.

Hoffe konnte dir helfen, im Englischen werden Eigennamen nur groß geschrieben und Satzanfänge. Ich weiß nicht genau ob du aburdance meintest, aber es gibt jedoch das Wort "adburdance" nicht in der englischen Sprache.