Now that it’s time to be studying for finals the weather is finally starting to get nice. It is interesting how much better and happier many people seem now that the sun is out and the weather is warming up and starting to feel like spring. This made me think about how weather and what affects it can have on a person’s mood. Some people believe that sunlight increases the amount of vitamin D, and that this can be beneficial to health and boost a person’s mood. Others think that there is a genetic component to how a person will react to weather. Seasonal Affective disorder (SAD) is the disorder where certain seasons, usually winter, result in depression or lower energy in individuals. This disorder is much more rare down south than it is in northern states where up to 1 in 10 people have been suggested to have the disorder in some form. Interestingly some people experience SAD in summer and feel that the heat and long days makes them uncomfortable and feel “off.”
Some researchers have suggested that SAD could have an evolutionary component. Animals often change their behaviors during the winter seasons as a way to adapt to the seasons hardship. Their metabolism, activity, energy levels can decrease to conserve energy, which may be the original source of what some people experience.
One study looked at the effects on the brain of rats in an experiment that attempted to mimic winter and summer light conditions. They had two rat groups, one that received dim light and dark cycles and the other that received bright light and dark cycles to represent light during the winter and summer. They found that the winter light rat group expressed more depression-like symptoms when tested in water swimming tests and also found that the winter rats had a reduced number of orexinA immunoreactive neurons in their hypothalamus and dorsal raphe nucleus than the summer rats. This suggests that the orexinergic system could have a role in lights regulation of mood.
Interestingly while SAD is more common in northern climates where there are longer winter and colder weather, some of the happiest ranked places in the world are in northern territories. Countries like Sweden and Denmark are far north with long winters yet are supposedly home to some of the happiest people in the world. This seems to go against the idea of weather causing depression yet there could be other factors involved as well.
SAD can be treated with drugs such SSRI’s to treat the depression, but can also be treated with cognitive therapies and even light therapy in which an artificial light can be used to imitate the sun, which has been shown to have a significant positive effect for many people.

References:

Nesse, Randolphe M; Williams, George C (1996). Why We Get Sick (First ed.). New York: Vintage

Deats, S. P., L. Yan, and J. S. Lonstein. “Attenuated Orexinergic Signaling Underlies Depression-like Responses Induced by Daytime Light Deficiency.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 13 May 2014.