I am curious to hear more about your reference to propecia. I also have taken propecia for about ten years. I suffer from this weird depression, lack of interest in life, self destructive tendency that I haven't been able to treat. I stopped propecia for several months, but my condition didn't get better, so I assumed it's not the propecia.
The lack of interest is a side effect of dopamine depletion, so I ran a search under Propecia and dopamine and ran across this site. They talk about dopamine a lot and how to raise it. I have not been able to find a positive link yet, but if the drug does lower dopamine this would also account for the depression effect as well.