Gross
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For many, the transition from dreary winter days to the sunny months of spring brings lower levels of stress and consistently happier moods. The change in mood experienced by many is caused by more than seeing life in a new light — it is caused by the change in light itself.
To understand a human mood’s connection to light exposure, it is useful to examine the history and exploration of Seasonal Affective Disorder (seasonal onset depression, usually occurring in the winter months).
Seasonal Affective Disorder, or SAD, first was named and described by Norman E. Rosenthal of the National Institute of Mental Health in 1984 after he moved from South Africa to New York and noticed a predictable, seasonal change in mood and energy levels.
Rosenthal theorized, “The hormone melatonin, which is secreted at night, can be suppressed by light.
Studies also have shown that light influences serotonin and epinephrine pathways in the brain, the same neurotransmitter systems known to be affected in people with general depression.”
Melatonin plays a key role in regulation of circadian rhythm, including wake-sleep cycles. Serotonin helps in the nervous system to regulate mood, sleep and appetite.
Since Rosenthal’s first recognition of the possible link between a person’s exposure to light and mood, considerable research has validated his hypotheses. The modern theory with overwhelming research and support is that SAD is caused by a lack of serotonin and/or melatonin.
In 2007, Hari Manev of the University of Chicago Department of Psychiatry proved that mice incapable of turning serotonin into N-acetylserotonin express depression-like behavior.
Additionally, the link between pineal gland and retina activity is well-established. Melatonin production is known to be produced by the pineal gland in periods of low levels of light.
The lower the levels of light exposure in a person’s daily routine, the less serotonin and melatonin his or her body produces. Symptoms and cases of SAD become more prevalent in climates with longer winters.
For MSU students in the fall and winter, conditions are a dangerous cocktail for the overproduction of melatonin and serotonin. Between consistently overcast skies, daily schedules of classes, work, homework and getting enough sleep, time in the sun can be limited.
Unfortunately for studious and hardworking Spartans, indoor lighting doesn’t adequately suppress melatonin and serotonin. This would be obvious, if it were not for the human eye’s dirty habit of tricking the mind into thinking indoor lighting is comparable to outdoor sunlight.
The human eye adjusts to an astonishing range of lighting. Lux is a measure of illumination. One lux is equivalent to the illumination from a candle’s flame from one meter away. Illumination decreases exponentially with distance.
For scale, a dark room with just a TV on measures about 1 lux. Indoor lighting illuminates the average living room to an illumination of 40 to 100 lux.
In contrast, on a bright summer day when the sun is overhead, the brightness of looking toward the horizon ranges from about 10,000 to 15,000 lux.
Despite the eye possessing comparable vision in an indoor-lighted environment and outside on a cloudless, sunny day, predominantly outdoor daily routines expose the body to 100 to 375 times more light exposure than predominantly indoor daily routines.
As a result, exposure to light varies greatly with how much time a person spends outside in sunlight. Ambulatory Monitoring, Inc., a research apparatus production company often employed by NASA and the Department of Defense, developed a device named the Actillume to measure the average daily light exposure of the wearer.
In 1996, William Gruen, founder of Ambulatory Monitoring, administered the devices to 318 San Diego adult volunteers.
Gruen summarized the study, “We were quite astonished to learn that different people experience a thousand-fold range of lighting… The volunteers who received the brightest illumination (spending bright days outdoors) were experiencing about 1,000 times the light exposure of those who received the dimmest average lighting (spending time mostly indoors).”
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Incorporating exposure to sunlight into a daily routine can alleviate nagging lethargy and anxiety while regulating a healthy appetite and sleep cycle.
Something as simple as sleeping with a bedside window open to allow dawn’s light to be a natural alarm clock can greatly improve a diverse spectrum of psychological and physiological concerns.
Regularly going outside during hours of sunlight is an often-forgotten, crucial dimension of personal health.
Tyler Gross is a guest columnist at The State News and a social relations and policy junior. Reach him at grosstyl@msu.edu.
