November 03, 2008
Winter Depression Caused By Genetic Mutation?

Puppets, your environment yanks your chain down in winter if you have a mutation in your eye pigment that lets light intensity play puppeteer with your emotions. A mutation of a photopigment of the eye might contribute to the development of the form of depression called seasonal affective disorder (SAD).

A new study indicates that SAD may be linked to a genetic mutation in the eye that makes a SAD patient less sensitive to light.

"These individuals may require brighter light levels to maintain normal functioning during the winter months," said Ignacio Provencio, a University of Virginia biology professor who studies the genetics of the body's biological clock, or circadian rhythms.

Provencio and his colleagues have discovered that melanopsin, a photopigment gene in the eye, may play a role in causing SAD in people with a recently discovered mutation.

"We believe that the mutation could contribute to increasing the amount of light needed for normal functioning during winter for people with SAD," Provencio said. "Lack of adequate light may be a trigger for SAD, but not the only explanation for the disorder."

This mutation might not by itself cause winter depression. But it seems to boost the chances of SAD.

The study was conducted with several other institutions, including the National Institute of Mental Health. It involved 220 participants, 130 of whom had been diagnosed with SAD and 90 participants with no history of mental illness.

Using a genetics test, the study authors found that seven of the 220 participants carried two copies of the mutation that may be a factor in causing SAD, and, strikingly, all seven belonged to the SAD group.

"While a person diagnosed with SAD does not necessarily carry the melanopsin mutation, what we found strongly indicates that people who carry the mutation could very well be diagnosed with SAD," Provencio said. "We think that if an individual has two copies of this gene, he or she has a reasonable chance of having the disorder."

The researchers found that a person with two copies of the gene is five times more likely to have symptoms of SAD than a person without the mutation.

These results only strengthen the argument for using a bright light box to treat SAD. Do you get depressed in winter? Think about getting a light box to wake up to in the morning.

Share |      Randall Parker, 2008 November 03 10:48 PM  Brain Depression

Jake said at November 3, 2008 11:29 PM:

SAD is caused by Vitamin D deficiency and nothing else.

Bob Badour said at November 4, 2008 6:43 AM:

A light box in the morning just causes me to fall asleep. It's counter-productive. It only works for me in the evening like simulating a long summer night.


I take vitamin D supplements, and I still need a light box. In my case, SAD appears to be caused by a breakdown in circadian rhythms due to inadequate stimulation to the pineal gland and inadequate serotonin production.

Happycrow said at November 4, 2008 7:40 AM:

Anecdotally, that makes perfect sense to lil' ol' me. I'm happy as a clam with a silver-grey sky, and find Texas to be much, much too bright.

Now, as Technogypsy says, the plural of anecdote is not evidence....

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