Light therapy, in one form or another, has been used as a treatment for a number of conditions since ancient times. Nearly 2,000 years ago, Greco-Roman physicians were treating depression and lethargy with sunlight directed toward the eyes. During his Arctic expeditions in the 1890s, Frederick Cook, M.D., noticing the profound influences of light on the voyagers and Alaskan natives, described a syndrome characterized by depressed mood, fatigue, and loss of energy and sexual desire. In 1946, H. Marx reported the use of bright artificial light to treat four men who had become depressed during an Arctic winter.
Contemporary light therapy involves daily scheduled exposure to bright artificial light (Lam et al., 1999b; Partonen, 2001; Rosenthal and Matthews, 1999). The term light therapy is used to differentiate light therapy for psychiatric disorders from phototherapy for other conditions, such as hyperbilirubinemia or psoriasis.
Since the first study of light therapy in winter seasonal affective disorder (SAD) (Rosenthal et al., 1984), a syndrome in which depression developed during fall or winter and remitted the following spring or summer for at least two successive years, numerous studies have concluded that bright light therapy is an effective treatment for SAD (Lam et al., 1999b; Magnusson and Boivin, 2003; Oren and Rosenthal, 1992; Partonen, 2001).
Light therapy is commonly administered by means of a light box--a metal structure containing fluorescent tubes behind a plastic diffusing screen (Lam et al., 1999b; Partonen, 2001; Rosenthal and Matthews, 1999). The dose of light exposure can be measured with the intensity and duration of the exposure. Efficacy is dose dependent to some extent, with both duration and intensity being important. Many studies used 2,500 lux light that was usually administered for two to six hours per day (Lam et al., 1999b; Partonen, 2001). Studies of 10,000 lux fluorescent light yielded similar results to studies using 2,500 lux for two hours (Magnusson and Kristbjarnarson, 1991; Partonen, 2001; Terman et al., 1990). To some degree, there is an inverse relationship between the intensity used and the duration required. Thus, 30 minutes of exposure to 10,000 lux may be as good as two hours of exposure to 2,500 lux, although such a linear relationship does not necessarily apply (Rosenthal and Matthews, 1999). The 10,000 lux fluorescent light box is usually used in clinical practice (Lam et al., 1999b).
A number of studies have found that morning light exposure was superior to evening light exposure (Eastman et al., 1998; Lam et al., 1999b; Lewy et al., 1998; Terman et al., 1998). It is important to note that evening light exposure was still significantly superior to placebo (Eastman et al., 1998; Terman et al., 1998). It is reasonable to start light therapy with morning exposure. Light treatment should not be administered late in the evening because it may cause insomnia.
Studies suggest that younger age and atypical symptoms such as hypersomnia, increased appetite, weight gain and increased carbohydrate consumption are associated with good response to light therapy (Lam et al., 1999b). The early response to light therapy partially predicts long-term response (Sher et al., 2001). If replicated, this observation may provide a simple test that will allow clinicians to predict which patient will respond best to light therapy.
Before starting light therapy, an ophthalmologic consultation is recommended for patients with a pre-existing retinal or eye disease (e.g., retinal detachment, retinitis pigmentosa, glaucoma, previous cataract surgery and lens removal) or a systemic illness that affects the retina (e.g., diabetes mellitus) (Lam et al., 1999b; Partonen, 2001). Side effects of light therapy include headaches, eyestrain, fatigue and insomnia (Lam et al., 1999b; Partonen, 2001; Rosenthal and Matthews, 1999). Most of these side effects respond to dose reduction. Hypomania and mania are uncommon, but serious, side effects. If a patient has prior history of mania, the risk of switch into mania might be minimized with a mood stabilizer (Kripke, 1991; Lam et al., 1999b).
Bauer MS (1993), Summertime bright-light treatment of bipolar major depressive episodes. Biol Psychiatry 33(8-9):663-665.
Bauer MS, Kurtz JW, Rubin LB, Marcus JG (1994), Mood and behavioral effects of four-week light treatment in winter depressives and controls. J Psychiatr Res 28(2):135-145.
Eastman CI, Young MA, Fogg LF et al. (1998), Bright light treatment of winter depression: a placebo-controlled trial. Arch Gen Psychiatry 55(10):883-889 [see comments].
Enns MW, Levitan RD, Levitt AJ et al. (1999), Diagnosis, epidemiology, and pathophysiology. In: Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder, Lam RW, Levitt AJ, eds. Toronto: Clinical & Academic Publishing, pp20-63.
Epperson CN, Terman M, Terman JS et al. (2004), Randomized clinical trial of bright light therapy for antepartum depression: preliminary findings. J Clin Psychiatry 65(3):421-425.
Kendler KS (1998), Anna-Monika-Prize paper. Major depression and the environment: a psychiatric genetic perspective. Pharmacopsychiatry 31(1):5-9.
Kripke DF (1991), Timing of phototherapy and occurrence of mania. Biol Psychiatry 29(11):1156-1157 [letter].
Kripke DF (1998), Light treatment for nonseasonal depression: speed, efficacy, and combined treatment. J Affect Disord 49(2):109-117.
Lam RW, Carter D, Misri S et al. (1999a), A controlled study of light therapy in women with late luteal phase dysphoric disorder. Psychiatry Res 86(3):185-192.
Lam RW, Tam EM, Gorman CP et al. (1999b), Light treatment. In: Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder, Lam RW, Levitt AJ, eds. Toronto: Clinical & Academic Publishing, pp64-88.
Lam RW, Terman M, Wirz-Justice A (1997), Light therapy for depressive disorders: indications and efficacy. Mod Probl Pharmacopsychiatry 25:215-234.
Lambert GW, Reid C, Kaye DM et al. (2002), Effect of sunlight and season on serotonin turnover in the brain. Lancet 360(9348):1840-1842.
Levitt AJ, Joffe RT, Kennedy SH (1991), Bright light augmentation in antidepressant nonresponders. J Clin Psychiatry 52(8):336-337.
Lewy AJ, Bauer VK, Cutler NL et al. (1998), Morning vs evening light treatment of patients with winter depression. Arch Gen Psychiatry 55(10):890-896 [see comments].
Magnusson A, Boivin D (2003), Seasonal affective disorder: an overview. Chronobiol Int 20(2):189-207.
Magnusson A, Kristbjarnarson H (1991), Treatment of seasonal affective disorder with high-intensity light. A phototherapy study with an Icelandic group of patients. J Affect Disord 21(2):141-147.
Oren DA, NE Rosenthal NE (1992), Seasonal affective disorders. In: Handbook of Affective Disorders, 2nd ed., Paykel ES, ed. London: Churchill Livingstone pp551-567.
Oren DA, Wisner KL, Spinelli M et al. (2002), An open trial of morning light therapy for treatment of antepartum depression. Am J Psychiatry 159(4):666-669.
Partonen T (2001), Light therapy. In: Seasonal Affective Disorder. Practice and Research, Partonen T, Magnusson A, eds. New York: Oxford University Press, pp65-78.
Partonen T, Leppamaki S, Hurme J, Lonnqvist J (1998), Randomized trial of physical exercise alone or combined with bright light on mood and health-related quality of life. Psychol Med 28(6):1359-1364.
Rosenthal NE, Matthews JR (1999), Seasonal affective disorder and light therapy. In: Encyclopedia of Neuroscience, 2nd ed., Adelman G, Smith BH, eds. Amsterdam, Netherlands: Elsevier, pp1828-1831.
Rosenthal NE, Sack DA, Gillin JC et al. (1984), Seasonal affective disorder: a description of the syndrome and preliminary findings with light therapy. Arch Gen Psychiatry 41(1):72-80.
Sher L (2001), Genetic studies of seasonal affective disorder and seasonality. Compr Psychiatry 42(2):105-110.
Sher L (2003), Bright light, serotonin turnover, and psychological well-being. Can J Psychiatry 48(7):499 [letter].
Sher L, Matthews JR, Turner EH et al. (2001), Early response to light therapy partially predicts long-term antidepressant effects in patients with seasonal affective disorder. J Psychiatry Neurosci 26(4):336-338.
Sher L, Oquendo MA, Galfalvy HC et al. (2004), A study of seasonal effects on cortisol and prolactin levels in patients with major depression and healthy volunteers. Biol Psychiatry 55(8 suppl 1):86S.
Terman JS, Terman M, Schlager D et al. (1990), Efficacy of brief, intense light exposure for treatment of winter depression. Psychopharmacol Bull 26(1):3-11.
Terman M, Terman JS, Ross DC (1998), A controlled trial of timed bright light and negative air ionization for treatment of winter depression. Arch Gen Psychiatry 55(10):875-882 [see comments].
Tuunainen A, Kripke D, Endo T (2004), Light therapy for non-seasonal depression. Cochrane Database Syst Rev 2:CD004050.