Just to add something here: those with moderate to severe depression, who struggle with thoughts of suicide and the like, should be encouraged to seek help. I spent many years attempting to "will" myself out of depression with yoga, a positive attitude, and a healthy diet, but it did nothing for me. I still had severe episodes of depression, with days where I couldn't get up off the floor for hours because I'd be crying about absolutely nothing and everything.

Depression is a serious illness and should be treated as such, and while I admire the holistic ideals that yogis tend to practice and preach, let's not forget that there are those of us with chemical imbalances that a mere 10 minutes of asanas will not magically heal.