Late fall and winter bring us the shortest days of the year. Our opportunities for exposure to sunlight, especially in regions with inclement weather, become limited. However, scientists have known for many decades that sunlight is beneficial to our health.
As the nights become longer, you may want to look into the benefits of bright light therapy (BLT). In helping to regulate your body’s circadian rhythm, BLT offers improvement in a variety of mental health conditions, including seasonal affective disorder (SAD), bipolar disorder, depression, insomnia, dementia, and attention-deficit hyperactivity disorder.
What is bright light therapy?
Bright light therapy, also called light exposure therapy, light therapy, circadian light therapy, and phototherapy, has been the first option of treatment for SAD for several decades.
In a bright light therapy session, you sit in front of a special light box that is set approximately 18 to 24 inches away from your face. You are exposed to the light for a specific period each day, typically in the morning at home. The frequency and duration of the therapy is determined by your doctor or other mental health professional.
The light is very similar to natural sunlight but without harmful UV rays. A single session may last from 20 to 40 minutes, typically at an intensity of 10,000 lux. The signals that the light sends to your brain triggers certain brain chemicals, which can improve your circadian rhythm and boost your mood. Studies show that side effects are mild in some cases (headache, nausea, jumpiness).
Seasonal affective disorder
Seasonal Affective Disorder (SAD) is sometimes called winter depression or seasonal depression because it occurs most frequently during the autumn and winter seasons when nights are the longest. While scientists are still trying to pinpoint the exact cause of SAD, researchers believe that the decreased sunlight may trigger the onset of a SAD episode.
SAD generally has symptoms that are depressive in nature: losing interest or pleasure in activities previously enjoyed, feelings of sadness, fatigue, low self-esteem, changes in appetite, difficulty concentrating or making decisions, and sometimes suicidal ideation. Weight gain is common with SAD because of higher cravings for carbs and an increase in sleep. Symptoms typically last around 40% of the year.
In approximately 10% of people suffering from SAD, the disorder occurs during the spring and summer months. Symptoms resolve during the fall and winter. These individuals usually have a loss of appetite and insomnia. 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?
Scientists are working to identify the exact cause of SAD. It is a complex condition with a combination of factors. The decrease in sunlight may disrupt your body’s circadian rhythm and lead to feelings of depression. A drop in serotonin levels also may factor in. Reduced sunlight can cause a drop in serotonin, which can trigger depressive symptoms. The seasonal change can also alter your body’s melatonin levels, which can disrupt sleep patterns and mood. Additional contributing mechanisms may include neurotransmitter dysfunction, retinal sensitivity to light, and genetic variations affecting circadian rhythms.
Studies on SAD and bright light therapy
Studies show that consistent use of bright light therapy is an effective treatment for SAD. One study examining SAD patients who underwent BLT found an 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.
Bright light therapy for mood disorders, insomnia, dementia, and ADHD
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.
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, bipolar depression, premenstrual depression, antepartum depression, and sleep disturbances.
Insomnia and dementia
Light therapy can be 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.”
Sleep disturbances are a key symptom of dementia after impaired cognition. The most problematic sleep disturbances are found in Alzheimer’s disease. A small 2016 study in Psychogeriatrics using bright light therapy showed improvement of sleep disturbances in patients with mild to moderate Alzheimer’s disease. This is promising news, although more research is needed.
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 2017 study in the Journal of Psychiatric Research. These results are promising for further investigation in larger studies.
The benefits of bright light therapy
Although the current research shows BLT to be effective, doctors and mental health providers do not use it as often as they could. With increased awareness and education, more people struggling with SAD and other mental health conditions may be helped through bright light therapy. It’s an option over pharmaceuticals or as an adjunct treatment with conventional medications.