Because depression does not have one concrete cause, different types of treatment are used to improve symptoms. One treatment is light therapy, or phototherapy, which uses a "device that contains white fluorescent light tubes covered with a plastic screen to block ultraviolet rays," according to the Cleveland Clinic. This device emits a light intensity of 10,000 lux, the equivalent of daylight on a clear day, the University of Pennsylvania explains. Light therapy is used to treat two forms of depression: seasonal affective disorder and bipolar depression.
Effects on Seasonal Affective Disorder
Seasonal affective disorder (SAD) differs from other forms of depression, as the patient has symptoms only during certain times of the year, most commonly in winter. The Cleveland Clinic states that SAD may be caused by a decrease in light in those months, which affects the patient's biological clock; that change also can affect the patient's mood. When a SAD patient undergoes light therapy, she receives 30 minutes of light exposure. The Clinic notes that symptoms improve, either through the light resetting the patient's circadian rhythms or correcting a serotonin imbalance in the brain. Regular sunlight exposure also can help with symptoms and prevent recurring depressive episodes.
Effects on Bipolar Depression
A patient with bipolar disorder has both mania and depression and can cycle between mood highs and lows. Bipolar depression can be difficult to treat. For example, antidepressants, which are used to treat other forms of depression, can trigger mania in a bipolar disorder patient.
Science Daily notes that as with SAD patients, bipolar disorder patients can be affected by a change in season. The University of Pittsburgh School of Medicine's Western Psychiatric Institute and Clinic studied the effects of light therapy on nine female bipolar patients. Six had a positive response, with some having a significant improvement; however, three women who received the light therapy in the morning had mania and depression symptoms at the same time, according to Science Daily.
Negative Effects
Light therapy does have side effects. Cleveland Clinic notes that it can cause insomnia, fatigue and irritability, which also are seen in depression; if the patient already has those symptoms, light therapy may make them worse. Other negative effects of light therapy include eye strain and headaches.
