circumstances, history and chemicals

my cousin's recent suicide attempt and this morning's good mood lead me to this discussion of the causes of depression:

there are three causes to depression: circumstances: unemployment, loneliness and a difficult dilemma which can lead to depression.

then there is history: low self esteem created by circumstance and anger at people that gets misdirected inward.

then there are chemicals: staying up late can produce chemicals that make one feel better. in that case the chemicals either override the other causes or put the causes in a different perspective.

i have woken up from too much sleep and thus the drugs in my brain that after a long sleeplessness make me feel better are lacking and in their place is just blah and circumstances and history.