How Sunshine Affects Your Mental Health

Light from the sun controls almost all the basic biological functions of life. It controls metabolism, how alert we are, how soundly we sleep, when we eat, our moods and much else besides. It could also be a risk factor for dementia later in life.

Each of us has a circadian rhythm or body clock that’s on a 24 hour schedule tied to the rising and setting of the sun.

When sunlight hits the photoreceptors (i.e. light receptors) in the retina of the eye, the light signal travels by way of the optic nerve to the hypothalamus. The main body clock is located within this region of the brain.

But we also have other circadian clocks in other parts of the brain and scattered throughout the body, even in our skin cells. Some are under the control of genes known as clock genes. Sometimes these circadian rhythms can get out of synchronization with the cycle of light and dark and even with each other. This can create both physical and mental health problems.

Night Shift Workers Are at Risk For Serious Health Problems

Human beings are designed to sleep when it’s dark, not stay up and watch Leno or Letterman. The introduction of the electric light bulb about a hundred years ago has greatly disrupted our natural patterns. It’s well known that night shift workers, for instance, have a greater likelihood of developing gastrointestinal diseases as well as diabetes, heart disease and even cancer. This is a fact, not the invention of back-to-nature enthusiasts.

When your circadian rhythm is synchronized with your daily life, there’s a good chance you’ll experience a vibrant mood. But millions of people have a dysfunction in their body clocks and experience sluggishness, depression, poor memory and dementia.

You may also have heard of the syndrome called seasonal affective disorder (SAD). It’s a good idea to be aware of this danger, as the days grow shorter for most of the people reading this. SAD befalls people who are very sensitive to changes in the length of the day. In the winter their biological clocks are telling them to hibernate, in conflict with the needs of their daily lives that require them to stay active.

People who suffer from SAD can become very lethargic, where almost any physical activity seems like too much effort. So if your mood darkens or your energy level seems to fall off during the winter, you may want to get those special sunshine-mimicking lights for home use.

Bright light treatment using a light box designed to mimic natural sunshine is becoming an increasingly popular way of treating mood-related conditions caused by circadian rhythm dysfunction.

Other Types of Mood Disorder Are Also Affected By Light

In non-seasonal depression – the regular kind, you might say — a study found that severely depressed patients’ circadian clocks were so disrupted that the night pattern of gene activity looked like the day pattern and vice versa. These people were, in effect, living in a different time zone.

Circadian rhythms may play a vital role in learning and memory. Tests with hamsters found that, without a functioning circadian system, the little animals can’t remember what they’ve learned. Lead researcher Norman Ruby said that “the degradation of circadian rhythms in elderly people may contribute to their short-term memory problems.” Similar disruptions have also been observed in patients with dementia and Alzheimer’s disease.

A simple circadian rhythm imbalance can be stimulated to reset itself by exposure to light. Swiss scientists found that the level of alertness, as well as cognitive performance, could be influenced by the intensity of light exposure that healthy volunteers were subjected to.

A study involving dementia patients found that exposure to bright light during daylight hours from both the sun and added indoor lighting decreased mental deterioration by 5% compared to patients who were not exposed. The patients who received more sunlight – real or simulated — also suffered fewer depressive symptoms and enjoyed more ability to cope with day to day living.

Circadian rhythms tend to “flatten out” as we get older, so getting outdoors and soaking up light for several hours a day is a simple and cost-free way to help keep yourself mentally alert, maintain your memory and stay in an all-around good mood.

And during the night time, turn out the lights, turn off the TV – and sleep. Lay off the caffeine, if that’s what it takes. And if you wake up in the dead of night and have trouble getting back to sleep, stay in bed anyway until you do. As we get older, getting a good night’s sleep may require more effort. You have to work at it a little. It’s highly recommended that you do so.


  1. http://www.ncbi.nlm.nih.gov/pubmed/23671070
  2. http://www.ncbi.nlm.nih.gov/pubmed/18832172
  3. http://www.ncbi.nlm.nih.gov/pubmed/22201280
  4. http://www.ncbi.nlm.nih.gov/pubmed/18544724