Bright light therapy is a common treatment for seasonal affective disorder and for circadian rhythm disorders.

Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light -- by a so-called light box. The light is administered for a prescribed amount of time and, in some cases, at a specific time of day. Light therapy directed at the skin is used to treat Acne vulgaris and neonatal jaundice. Light therapy which strikes the retina of the eyes is used to treat circadian rhythm disorders such as delayed sleep phase syndrome and can also be used to treat seasonal affective disorder, with some support for its use also with non-seasonal psychiatric disorders.

[edit] Skin related

[edit] Acne vulgaris

Sunlight was long known to improve acne, and this was thought to be due to antibacterial and other effects of the ultraviolet spectrum; which cannot be used as a treatment due to the likelihood of skin damage in the long term. However, artificial UV didn't work as well as sunlight.

It was found that some of the visible violet light, present in sunlight, in the range 405-420 nm activates a porphyrin (Coproporphyrin III) in Propionibacterium acnes which damages and ultimately kills the bacteria by releasing singlet oxygen. A total of 320 J/cm² of light within this range renders the bacteria non-viable.^[1]

Deep penetrating light therapy for 3 consecutive days has been shown to reduce the bacteria in the pores by 99.9%. Since there are few porphyrins naturally found in the skin, the treatment is believed safe except in patients with porphyria;^[2] although eye protection is used due to light-sensitive chemicals in the retina. The light is usually created by fluorescent lamps, bright LEDs or dichroic filament bulbs.

Overall improvements of on average 76% for 80% of patients occurs over 3 months; most studies show that it performs better than benzoyl peroxide and the treatment is far better tolerated. However, approximately 10% of users see no improvement.^[1]

[edit] Psoriasis and eczema

A feature of psoriasis is localised inflammation mediated by the immune system. UV radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis or eczema use UVA (315-400 nm waveband) or UVB (280-315 nm waveband) light waves. UVA, combined with a drug taken orally, is known as PUVA treatment. Narrow Band UVB is the 310 nm wave length and is given as a light therapy treatment rather than full spectrum UVB.

[edit] Tanning

Tanning is caused by the effects of two different spectrums of ultraviolet radiation: UVA and UVB.

[edit] Wound healing

Light therapy has been suggested used for the healing of wounds. Some^[3] say that it does not appear to be effective, while others^[4] find that it can be effective.

[edit] Photodynamic therapy

Visible blue light is used with aminolevulinic acid for the treatment of Actinic keratosis. This is not a U.S. FDA-approved treatment for acne vulgaris.^[5]

[edit] Mood and sleep related

[edit] Light boxes

For the purpose of manipulating melatonin levels or timing, light boxes providing intense artificial illumination are effective.^{[citation needed]} These lamps, at a prescribed distance and within peripheral vision, provide up to 10,000 lux to the user's eyes, without harmful ultraviolet radiation.

The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness. To some degree, the reverse is true for serotonin, which has been linked to mood disorders.

A lower intensity of certain wavelengths of light in the blue end of the electromagnetic spectrum, about 480 nm, may be as efficacious as high-intensity white light.^[6]

[edit] Seasonal affective disorder

While full sunlight is preferred for seasonal affective disorder (SAD), light boxes may be effective for the treatment of the condition. The United States Food and Drug Administration has not approved the use of light boxes to treat SAD due to unclear results in clinical trials,^[7] but light therapy is still seen as the main form of treatment for SAD.^[8]

It is possible that response to light therapy for SAD could be season dependent.^[9]

[edit] Non-seasonal depression

Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric distrubances, including major depressive disorder, bipolar disorder and postpartum depression.^[10][11]

[edit] Circadian rhythm sleep disorders

[edit] Chronic CRSD

In the management of circadian rhythm disorders such as delayed sleep phase syndrome, the timing of light exposure is critical. For DSPS, the light must be provided as soon after spontaneous awakening as possible to achieve the desired effect, as shown by the phase response curve for light in humans. Some users have reported success with lights that turn on shortly before awakening (dawn simulation). Morning use may also be effective for non-24-hour sleep-wake syndrome, while evening use is recommended for advanced sleep phase syndrome.

[edit] Situational CRSD

Light therapy has been tested for individuals on shift work,^[12] and for jet lag.^[13]

[edit] Neonatal jaundice

A newborn infant undergoing white-light phototherapy to treat neonatal jaundice.

Light therapy is used to treat cases of neonatal jaundice^[14] through the isomerisation of the bilirubin and consequently transformation into compounds that the newborn can excrete via urine and stools.

[edit] Parkinson's disease

Bright light therapy may ease Parkinson's disease by reducing patients' tremors.^[15][16]

[edit] Safety

Ultraviolet light causes progressive damage to human skin. This is mediated by genetic damage, collagen damage, as well as destruction of vitamin A and vitamin C in the skin and free radical generation. Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration.^[17]

Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorders either filter out or do not emit ultraviolet light and are considered safe and effective for the intended purpose, as long as photosensitizing drugs are not being taken at the same time and in the absence of any existing eye conditions. Light therapy is a mood altering treatment, and just as with drug treatments, there is a possibility of triggering a manic state from a depressive state, causing anxiety and other side effects. While these side-effects are usually controllable, it is recommended that patients undertake light-therapy under the supervision of an experienced clinician, rather than attempting to self-medicate.^[18]

It is reported that bright light therapy may activate the production of reproductive hormones, such as testosterone, luteinizing hormone, follicle-stimulating hormone, and estradiol.^[19][20]

There are few absolute contraindications to light therapy, although there are some circumstances in which caution is required. These include when a patient has a condition that might render his or her eyes more vulnerable to phototoxicity, has a tendency toward mania, has a photosensitive skin condition, or is taking a photosensitizing herb (such as St. John's wort) or medication.^[21] Patients with porphyria should avoid most forms of light therapy. Patients on certain drugs like methotrexate or chloroquine should use caution with light therapy as there is a chance that these drugs could cause porphyria.

[edit] Side effects

Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, and nausea. Some nondepressive physical complaints (such as poor vision and skin rash or irritation) may improve with light therapy.^[22]

[edit] See also

• Low level laser therapy
• Deep penetrating light therapy

[edit] References