This is an interesting theory. However, one can argue on the other end that the act and release of sexuality decreases depression because it releases endorphins. If someone has an increased sex drive, they are more likely to have sex or masturbate. No matter what way the sexual pleasure is achieved, endorphins are released, thus making an individual happier, so in a weird way could SSRI's also be hurting the bodys natural way of becoming happy?
Penguin I agree with you. The reason I put "happiness" in quotes is because I don't believe that the state of mind achieved through use of antidepressants is happiness, is it merely the perceived removal of depression, leaving the person using them in a pleasantly apathetic state.
Which brings another interesting point to light...
Seeing as endorphins is a natural pain killer...would that not be the drive and/or urge behind self-injury? Seeing that if you hurt your self, your body produces endorphins to kill the pain and thus giving a feeling of "well-being"?