While not always, you would be surprised how often depression is a consequence of inactivity or not enough direct sunlight on the skin.
I get depressed when i sit in the house to much, even though i much prefer being indoors.
I start to get depressive after anywhere from 3-10 days of being inside with few to no adventures outside in the daylight.
Luckily for me, my dayjob forces me to be in the sun 12 hours a day, and when im working i NEVER get depressed.
Im no doctor so take this with a huge grain of salt, but depression in many forms is a consequence of inactivity and to much leisure time in the form of non physical activity.
Not all depression can be "cured" by being more active, but you would do yourself a good favor by getting out there being active and talking to people. Talk to rote nerds if you need to.
And i believe that if this forum is one of the only places you actually talk to people then its a mistake to leave it. I think you should become even more active... Perhaps in the lore or offtopic forums where people tend to make friends a bit more rather than in gameplay general where everyone is like a wolf on the prowl.
But yeah, if you look at people, even though there is no direct 1-1 correlation, very busy/active people tend to be at least outwardly depressed alot less... Its simple why as well.... They just dont have time for it.
Like myself when im busy... Im never depressed. Im only ever really depressed when im lazing around on the couch or in bed playing games or watching to many movies/tv.
My $.02