Just in time for the winter solstice, scientists may have figured out how short days can lead to dark moods.
Two recent studies suggest the culprit is a brain circuit that connects special light-sensing cells in the retina with brain areas that affect whether you are happy or sad.
When these cells detect shorter days, they appear to use this pathway to send signals to the brain that can make a person feel glum or even depressed.
“It’s very likely that things like seasonal affective disorder involve this pathway,” says Jerome Sanes, a professor of neuroscience at Brown University.
A few weeks earlier, a different team published a study suggesting a very similar circuit in mice.
Together, the studies offer a strong argument that seasonal mood changes, which affect about 1 in 5 people, have a biological cause. The research also adds to the evidence that support light therapy as an appropriate treatment.
“Now you have a circuit that you know your eye is influencing your brain to affect mood,” says Samer Hattar, an author of the mouse study and chief of the section on light and circadian rhythms at the National Institute of Mental Health. The finding is the result of a decades-long effort to understand the elusive link between light and mood. “It is the last piece of the puzzle,” Hattar says.
Read full, original post: Scientists Find A Brain Circuit That Could Explain Seasonal Depression