Sunshine actually may put pep in your step and improve your thinking skills. A study by the University of Alabama at Birmingham shows that the amount of sunlight you are exposed to may boost your cognitive ability.

The study examined the seasonal role and amount of sunlight exposure (referred to as insolation) on patients’ energy levels and cognitive ability. Researchers hypothesized that greater insolation would boost both energy and mental functioning.

This was found to be very true for patients with depression. Sunlight plays a huge role in the body’s circadian (daily) rhythm. Alzheimer’s, for example, has been associated with low blood flow to the cerebrum, yet another of sunlight’s effects.

Individuals who got less sun exposure were more likely to experience an irregular circadian rhythm, similar to Seasonal Affective Disorder (SAD), also known as seasonal depression. Several studies have been conducted in the past to examine the effect of sunlight and seasonal changes on mood in people with depression, but this was the first to study the effects of both on thought processes.

"We think some of the same physiological mechanisms that affect depression also affect cognitive function,” says Shia Kent, author of the study and doctoral candidate at the School of Public Health at the University of Alabama at Birmingham. “These same hormone systems have been implicated in a number of mental disorders and cognitive disorders.”

One key to this relationship lies in the suprachiasmatic nuclei (SCN), a region of the brain responsible for processing information from the eyes and stimulating hormones.One of the SCN’s roles is to prevent the pineal gland from converting serotonin into melatonin, a hormone that triggers sleepiness.

The retina sends light information to the SCN, slowing the brain’s production of melatonin and serotonin—both associated with cognitive functioning—during the day or in a well-lit room. Without this process, the body’s natural rhythm is disrupted. Similar disruptions have been associated with sleep disorders and memory problems in otherwise healthy individuals.

Participants in the study hailed from an area of the United States known as the “stroke belt”—Arkansas, Louisiana, Tennessee, Mississippi, Alabama, Georgia, North Carolina, and South Carolina. Nearly 14,500 men and women over age 45 (44% African-American, 56% white) with no history of a stroke included in the final model were questioned using the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study.

Cognitive functioning was measured via telephone interviews, while weight, height and blood pressure were measured in-home prior to the study. Participants were then followed for the next two weeks, while researchers measured insolation (with the help of NASA satellite and ground data) and thinking ability (using questionnaires).

Solar radiation was measured eight times daily, at 3-hour intervals. Typical insolation values were 25,000-30,000 KJ/m² in late spring and early summer, and 8,000-10,000 KJ/ m² in the central U.S. Short-term and long-term memory were measured using a six-question test. Answering four or less correctly indicated impairment. 

Based on their findings, researchers reported that low sunlight exposure was a higher likelihood of cognitive impairment for subjects with depression, including those who were prone to SAD. Roughly 18% of participants with any form of depression were classified as having impaired thinking in response to lower insolation, regardless of the season.

“This is speculation,” says Kent, “but those who have cognitive impairment could be helped with sunlight."

 

Learn more about Seasonal Affective Disorder (SAD) in Healia Communities.