I can already tell that my moods are changing, and it's not a coincidence that the days are getting shorter and the summer's bright sunlight is often giving way to gray or cloudy skies.
I also have the constant urge to turn on every light in the house and leave them on all day, despite the fact that it's not at all environmentally conscious -- or helpful to the electric bill!
I have seasonal affective disorder, which means that my moods and, seemingly, my entire daily world respond to bright light -- or a lack of it. It's taken me a couple of decades to realize it wasn't just moodiness, but rather a continual cycle that follows the seasons.
Here's what the Mayo Clinic says about SAD:
"Seasonal affective disorder is a cyclic, seasonal condition. This means that signs and symptoms usually come back and go away at the same times every year. Usually, seasonal affective disorder symptoms appear during late fall or early winter and go away during the warmer, sunnier days of spring and summer. But some people have the opposite pattern, developing seasonal affective disorder with the onset of spring or summer. In either case, problems may start out mild and become more severe as the season progresses.
"Fall and winter SAD (winter depression)
"Symptoms of winter-onset seasonal affective disorder include:
Depression
Hopelessness
Anxiety
Loss of energy
Social withdrawal
Oversleeping
Loss of interest in activities you once enjoyed
Appetite changes, especially a craving for foods high in carbohydrates
Weight gain
Difficulty concentrating and processing information."
What causes SAD? Experts aren't entirely sure. Like a lot of things, the equation adds up to a lot of individual factors: your genetic history, your body's circadian rythym and your chemical makeup, for instance.
The important thing is that if you have large mood swings when the seasons change, you don't have to feel that way forever. Treatment can include drugs and/or light box therapy; it's worth checking with your doctor if you think you might be affected this way. Some people think they should just be able to "snap out of it," but there's a lot more to it than that. (If I could, I would, believe me.)
Here's the Mayo Clinic's page on SAD, with links to treatment and support pages:
http://www.mayoclinic.com/health/seasonal-affective-disorder/DS00195