In a Weather.com poll, 69% of people said they are in a better mood when the sun is shining, compared to 24% who said the sun doesn't affect their mood and 7% were unsure. Of course, these results are not scientific and those drawn toward Weather.com are not necessarily a typical audience. In any case, seasonal affective disorder (SAD) is real and is also known as the "winter blues". It's when people experience depressive symptoms due to lack of sunshine. SAD is almost nonexistent in the tropics.