I think there is a drastic change in many respects regarding overpopulation, of the human race I take it.
Do over populated areas trully have more suicides, more bisexual behavior, etc?
Sure, but that is just basic statistics. More people equals more of any human outcome.
Does overpopulation cause more suicide, psychologically?
Probably. With less privacy, more pressure, faster paced societies, often centralized weath and power creating larger poverty levels, etc. But plenty of hermits kill themselves.
But we are social creatures, though resistant to change, we are highly adaptive when basic survival is at stake.
Families of 10-14 kids work just as well as single child homes, maybe even better.
I think the important impacts on psyche from overpopulation comes from unseen or ignored environmental effects.
From the quality and availability of living space and resources such as food, air, and water. Septic and Sanitation are always key problems of overpopulation as well.
But suicide and psychological effects seem to occur in all sizes of communities, and grow or shrink in direct proportion to them. That and they grow and shrink in response to key factors, such as poverty, nutrition, opression, slavery, war, etc.