There is certainly a correlation between lesbianism and depression. A causes B? or B causes A? or C causes both A and B? I don't know.
I have long thought that in some cases, and some cases only, that gay behavior is an adrenalin-producing self-medication some teens use to counteract severe depression. Political correctness says that homophobia makes gay teens suicidal, but it could be the reverse -- the gay issue is not a cause of depression, but a symptom of depression.
Unfortunately, between the drumbeat of propaganda, the bullying and the lockstep demanded by law of psychologists these days, anyone who would try to advance this theory is pretty much hamstrung.