Light Therapy - What It Is and What It Treats

Light therapy, or phototherapy, is used to treat a variety of disorders in the body and mind.

What is Light Therapy?

Light therapy (phototherapy, heliotherapy) is the use of exposure to “specific wavelengths of light”. This can include daylight, lasers, polychromatic polarized light, fluorescent lamps, light-emitting diodes (LED), full-spectrum light, and dichroic lamps. The light is used under controlled conditions, as a prescription. Light therapy is now commonly used for a variety of conditions, including psoriasis and other skin disorders (i.e., jaundice in babies, eczema, acne, etc.), sleep disorders (such as circadian rhythm disorder), and psychological issues, such as seasonal affective disorder (SAD).¹

Body Conditions Treated

For the skin disorders, patients may be treated with targeted phototherapy so that UV ray exposure doesn’t lead to skin cancer. Non-targeted phototherapy would be from sunlight. The advantage of targeted light therapy is that higher dosages of light can be given, since the whole body isn’t put at risk, allowing skin conditions to be treated quickly. With psoriasis, for example, UV radiation can reduceinflammatory response by suppressing the immune system. Neonatal jaundice is another condition that benefits from light therapy, such as seating a baby near a window for a prescribed amount of time or through the use of a “bili light” to allow bilirubin in the infant’s body to be excreted. Any light treatment needs to protect the eyes from phototoxicity.² UV exposure, long term, can contribute to cataracts and skin problems. Tanning beds are not the same thing as light box therapy. Ironically, UV light therapy may help treat some kinds of skin cancer, via “ultraviolet blood irradiation”. The FDA has approved this for T-cell lymphoma. Photopheresis can also be used for transplant rejection. Trials are underway to see if this therapy is beneficial for rheumatoid arthritis, lupus, Type 1 diabetes, multiple sclerosis, and systemic sclerosis.³

Treating the Mind with Light Therapy

Light therapy can treat seasonal affective disorder, major depression, postpartum depression, and bipolar disorder. In the case of SAD, full sunlight may be unavailable; therefore special light boxes can deliver light where the UV has been largely filtered out (UV light can cause skin and eye damage). Phototherapy may reset the internal clock of the body, and this can help people with sleep disorders, too, such as circadian rhythm sleep disorder (CRSD). CRSD can be chronic or situational (i.e., jet lag, shift workers). In treating CRSD or delayed sleep phase disorder (DSPD), “the timing of light exposure is critical”. The sleep regulating hormone, melatonin, is produced during darkness, not light. Light boxes can manipulate melatonin production. It is important to make sure that patients use the lights as prescribed. Phototherapy alters the mood, and too much exposure can trigger anxiety and mania. Patients should not take St. John’s Wort while using light therapy, as that herb is photosensitizing. There are also certain other herbs and medications (i.e., methotrexate, chloroquine) that are contraindicated with phototherapy.⁴ A benefit of bright light therapy for depression, though, includes the ability to enhance or avoid medications. For example, pregnant and breastfeeding patients may prefer phototherapy over prescriptions. The type of light therapy for psychological conditions does not contain the UV light used to treat skin conditions. Still, there are other side effects possible, such as headaches, nausea, irritability, eyestrain, and agitation. Euphoria would be a particular concern in bipolar disorder. It is also important to remember that tanning beds are not an alternative to light therapy. Tanning beds increase skin cancer and skin damage risks.⁵