Originally Posted by
vashti 
This is speculation at best. Women are more likely to suffer from depression, and surprise! They are also subject to hormone fluctuations which correlate strongly to their symptoms.
They are more likely to suffer from depression because they are more sensitive than men, their sensitivity arouses depression symptoms (E.g Insomnia, Rumination etc..) which mostly create the chemical imbalance. Ofcourse there are other factors at play here as well, such as perception of and poor well being.
If you are interested I will post you some articles with links between depression and sensitivity. Sure there could be cases where people are just biologically stuffed up, but those cases are few and far between compared to the norm.