CLoudy day....

My mood seems to match today's weather..Feeling groggy when I woke up and as it started to rain and rain and rain....and when the sun began to hide behinds those big dark heavy clouds....thats when my mood turn cloudy and down. Few my friends whom I talked to seem to be in a groggy and low energy mood as well....is this how SAD(Seasonal Affective Disorder) patient feels?? They will feel down and "depress" when there is no sun, especially during winter... I wonder...how would sun or brightness affects one emotion...

emotions <-----> pituitary gland (secretion of hormone) - influence mood/emotion (serotonin)
emotions <-----> brightness (light/sun)

so, what's the connection between ...

brightness (light/sun) <----> pituitary gland (secretion of hormone) - influence mood/emotion
(serotonin)