Here is something to ponder, that I found to be a little amusing.

http://www.redorbit.com/news/health/1922017/vitamin_c_rapidly_improves_emotional_state_of_acutely_hospitalized_patients/index.html
http://www.redorbit.com/news/health/1831732/vitamin_d_can_improve_mood/index.html

*I wonder what conclusions can be drawn from it though.