Study ties sunlight to brain function

BIRMINGHAM, Ala., July 27 (UPI) -- A lack of sunlight can lead to reduced mental performance, not just mood disorders, among depressed people, a U.S. university study said Thursday.

"This new finding that weather may not only affect mood but also cognition has significant implications for the treatment of depression, particularly seasonal affective disorder," University of Alabama at Birmingham researcher Shia Kent said.

Seasonal affective disorder, also known as winter depression or winter blues, is a mood disorder in which people repeatedly experience depressive symptoms in the winter due to a lack of sunlight.

The university researchers used data from 14,474 people participating in a U.S. National Institutes of Health study to observe associations between depression, mental function and sunlight.

They measured short-term recall and temporal orientation.

Temporal orientation -- or the way individuals behave as a reflection of their consideration of the past, the present and the future -- is considered a basic dimension of human functioning.

The researchers confirmed that light affects brain blood flow, which is in turn linked to cognitive functions. It also regulates the hormones serotonin and melatonin.

Kent and his colleagues speculate in the journal Environmental Health that the physiological mechanisms that give rise to seasonal depression also contribute to diminished mental functioning among depressed people.