What influenced Van Gogh's style of painting?

I think his STYLE (not content/subject matter) was influenced most by his 1.) mental state (depressied/bi-polar/crazy), 2.) drug use (drank a LOT of absynthe which can stimulate/affect the optic nerve...aka: make you halluscinate, to a lesser degree i'd say he was also influenced by his impressionist peers. and as with any artist, i'm sure there are many experiences throughout hsi life from childhood till death which influenced his style.