WHAT IS BRIGHT LIGHT THERAPY?

Bright light therapy, also known as light exposure therapy, circadian light therapy, light therapy, and phototherapy, has been a first-line treatment for seasonal affective disorder for several decades.

During a light therapy session, patients sit in front of a special light box positioned 16 to 24 inches away from the face for a set amount of time each day, often in the morning at home. The duration and frequency of the therapy is determined by a medical doctor or mental health professional. 

The light therapy mimics natural outdoor light, but without the harmful UV rays. A session may last from 20 to 40 minutes, usually at the optimal intensity of 10,000 lux.

When the light sends signals to the brain, a number of brain chemical responses are triggered that can both uplift mood and help to beneficially impact an individual’s circadian rhythm (the sleep/wake cycle). Studies show only mild side effects (jumpiness, headache, nausea) in some cases.

SEASONAL AFFECTIVE DISORDER

Seasonal affective disorder (SAD) is a type of depression sometimes called seasonal depression or winter depression because the symptoms most often occur during the fall and winter months when there is less sunlight. While the cause of SAD is not entirely clear, researchers believe that the reduced sunlight in fall and winter may trigger winter-onset SAD. 

SAD is typically associated with depressive symptoms—feeling sad, losing interest or pleasure in activities once enjoyed, appetite changes, fatigue, feeling low self-esteem, trouble concentrating and making decisions, and even suicidal thoughts. In addition, weight gain is common with SAD due to increased cravings for carbohydrates and an increase in sleep. Symptoms last typically 40% of the year.

In roughly 10% of those with SAD, the disorder has the opposite seasonal pattern, occurring in the spring and summer months and going away during the fall and winter months. These individuals usually have a loss of appetite and sleep. In some people with bipolar disorder, spring and summer can bring on symptoms of mania or a less intense form of mania (hypomania), and fall and winter can be a time of depression.

A 2020 study estimates that SAD affects .5 to 2.4% of the population. It is more prevalent among younger people, women, and individuals in northern climates. 

WHAT CAUSES SEASONAL AFFECTIVE DISORDER?

The exact cause of SAD is not clear. It is a complex disorder resulting from a combination of factors. The decrease in sunlight may disrupt your body’s internal clock and lead to feelings of depression. A drop of serotonin levels also may factor in. Reduced sunlight can cause a drop in serotonin, which can trigger depressive symptoms. The seasonal change can also disrupt the body’s melatonin levels, which can impact sleep patterns and mood. Additional contributing mechanisms may include retinal sensitivity to light, neurotransmitter dysfunction, and genetic variations affecting circadian rhythms.

STUDIES ON BRIGHT LIGHT THERAPY AND SAD

The great news for those experiencing SAD is that consistent use of bright light therapy is an effective treatment. One study examining SAD patients who underwent BLT found immediate improvement in mood in as little as 20 minutes, and greater improvement with 40 minutes of exposure.

Another BLT study showed remission of SAD symptoms and an “antidepressant effect” over placebo after 3 weeks of regular light therapy treatments. A longer study that tracked SAD patients undergoing BLT for short-term (2-8 weeks) and long-term (fall and winter months for 3-6 years) treatment found that “light therapy yields about 75% clinical remissions” and was as effective as an antidepressant. 

Compelling research in a 2023 issue of Translational Psychiatry found that just four weeks of bright light therapy increased brain volume in an area associated with mood regulation and memory. The study involved 24 adults diagnosed with either major depression or bipolar disorder.

In the group that received bright light therapy, there were significant increases in the left hippocampal dentate gyrus as well as marked improvements in depressive symptoms.

BENEFITS OF LIGHT THERAPY FOR MOOD DISORDERS, ADHD, INSOMNIA, AND DEMENTIA

In recent years, bright light therapy has shown benefits for a number of additional mental health conditions—all of which are in some way impacted by disruption to a patient’s circadian rhythm.

Bright Light Therapy for Bipolar Disorder and Depression

Altered sleep patterns and disrupted circadian rhythms play a role in both bipolar disorder and depressive disorder. A 2020 meta-analysis was performed evaluating 12 bright light therapy studies involving 847 patients with bipolar disorder. The results showed that BLT significantly reduced the severity of bipolar depression.

An extensive review in Neuropsychobiology examined studies on bright light therapy for the treatment of mood disorders. It found substantial evidence for BLT efficacy in the treatment of chronic depression, antepartum depression, premenstrual depression, bipolar depression, and disturbances of the sleep-wake cycle. While more studies are recommended, this research is very promising.

Bright Light Therapy for ADHD

New research from the Netherlands has noted delayed circadian rhythms in individuals with ADHD. In fact, this study estimates a whopping 73–78% of children and adults with ADHD have the issue, which means they are night owls and don’t get sleepy or tired enough to fall asleep until 2 or 3 a.m. Hence, getting a good night’s sleep is an integral part of ADHD treatment.

Light therapy was used to treat ADHD in a 2006 pilot study. The study found the shift toward an earlier circadian preference with BLT was the strongest predictor of improvement on both subjective and objective ADHD measures. Similar findings were found in a more recent study in the Journal of Psychiatric Research. These results are promising for further investigation in larger studies.

Bright Light Therapy for Insomnia and Dementia

The Sleep Foundation touts light therapy as helpful to those who suffer from insomnia, especially sleeplessness that is linked to circadian rhythm sleep disorders. A 2016 review study on light therapy and sleep problems surveyed 53 studies with a total of 1,154 participants. It concluded that “light therapy is effective for sleep problems in general, particularly for circadian outcomes and insomnia symptoms.”

One of the main symptoms of dementia after impaired cognition is that of sleep disturbances. The most problematic sleep disturbances are found in Alzheimer’s disease. While more research is needed, a small 2016 study in Psychogeriatrics using bright light therapy showed improvement of sleep disturbances in patients with mild to moderate Alzheimer’s disease.

A BRIGHT FUTURE FOR LIGHT THERAPY

Despite the wealth of research showing its efficacy, this simple, non-drug therapy remains underutilized, according to a recent study. Hopefully with education and increased awareness, many more people struggling with seasonal affective disorder and other mental health issues can be helped by bright light therapy.