Why Am I So Irritable In The Winter?

Q: Is there anything that can be done for seasonal depression? The long months of overcast skies and reduced sunlight never had any noticeable effect on me in my youth, but as I approach middle age, I find I’m irritable, fractious, melancholy and generally about as pleasant as a plowed-up snake from about mid November until at least mid May. Last year was the worst ever. Since I plan to live through at least another 45 winters or so, it would sure be nice to know if there’s anything I can do about this. – Sean