Since then, however, two randomized, controlled trials with large sample sizes found that bright light therapy using fluorescent light boxes was superior to plausible placebo controls. (For clinical remission rates, please see the figure at <http://imaging.cmpmedica.com/CME/pt/content/sad.jpg>-Ed.) Terman et al. (1998) studied 144 patients randomly assigned to one of four treatments for two to four weeks: morning or evening bright light exposure (consisting of a 10,000 lux fluorescent light box for 30 minutes per day) or a negative ion generator that emitted either high-density or low-density negative ions (the placebo condition). Eastman and colleagues (1998) studied 96 patients randomized to four weeks of treatment with morning or evening bright light (consisting of a 6,000 lux fluorescent light box for 1.5 hours) or morning use of a deactivated negative ion generator (the placebo condition). In both studies, bright light was superior to the placebo condition in producing clinical remissions.
Two subsequent meta-analyses have also supported the efficacy of light therapy (Lee and Chan, 1999; Thompson, 2002). This evidence resulted in the recommendation of light therapy as a first-line treatment for SAD in expert and consensus clinical guidelines (Bauer et al., 2002; Lam and Levitt, 1999).
The recommended protocol for light treatment is 10,000 lux exposure, administered by a fluorescent light box with an ultraviolet filter, for at least 30 minutes per day in the early morning (Lam and Levitt, 1999). Less intense light usually requires greater duration of exposure for the same response, e.g., 3,000 lux for one to two hours. Naturalistic studies show a clinical response rate of about 67% using this protocol (Lam et al., 2000). Response to light therapy usually occurs rapidly, often within one week, although some patients may require two to four weeks of treatment before noticing a clear response. Patients generally relapse after light is stopped, so most patients must use the light box daily through the winter until the time of their natural spring remission. Patients then restart light therapy at the beginning of the next winter season, either prior to, or shortly after, onset of their symptoms.
The side effects of light therapy include headache, eyestrain, nausea, agitation, sedation and dizziness (Kogan and Guilford, 1998). These are usually mild and time-limited or improve with reducing the intensity or duration of light exposure. There have been rare reports of switching to mania or hypomania, and thus patients with BD should be followed closely. Patients with bipolar I disorder should take mood stabilizers while treated with light.
Studies of chronic use of light therapy have not shown any toxicity or damage to the eyes (Gallin et al., 1995), but patients with ocular risk factors (including pre-existing retinal disease; systemic diseases that affect the retina such as diabetes mellitus or lupus; past cataract surgery; advanced age; and photosensitizing medications such as lithium(Drug information on lithium), phenothiazine [Phenergan], melatonin(Drug information on melatonin), St. John's wort and antipsychotics such as thioridazine(Drug information on thioridazine) [Mellaril]) may have potential risks with bright light exposure. Hence, clinical guidelines suggest that these patients have a baseline ophthalmological evaluation and periodic monitoring (Lam and Levitt, 1999).
Novel treatments for SAD include dawn simulation, in which bedroom lights are gradually turned on to simulate a summer dawn (Avery et al., 2001), high-density negative ions (Terman et al., 1998) and exercise (Pinchasov et al., 2000). Light therapy is also being investigated for nonseasonal conditions, including jet lag, shift work, circadian sleep disorders, bulimia nervosa, premenstrual depressive disorder and nonseasonal depressive disorders (including antepartum depression) (Kripke, 1998; Lam, 1998a; Oren et al., 2002).
Antidepressants. Antidepressant medications have not been studied as extensively as light therapy in SAD. Selective serotonin reuptake inhibitors have the best-demonstrated evidence for medication efficacy. In one study, patients (n=68) were treated with fluoxetine(Drug information on fluoxetine) (Prozac) 20 mg/day for five weeks (Lam et al., 1995). The clinical response rate (>50% improvement in depression scores) of fluoxetine (59%) was significantly superior to placebo (34%). Smaller controlled studies show that other medications, including moclobemide(Drug information on moclobemide) (Aurorix, Manerix), L-tryptophan and St. John's wort, may be effective treatments for SAD (Lam and Levitt, 1999). There are also case studies suggesting that bupropion (Wellbutrin), citalopram(Drug information on citalopram) (Celexa), reboxetine(Drug information on reboxetine) (not approved for use in the United States) and tranylcypromine (Nardil, Parnate) are beneficial. Unfortunately, only one small study has directly compared light treatment to antidepressants (Ruhrmann et al., 1998). Forty patients with SAD were randomized to five weeks of bright light (3,000 lux fluorescent light box for two hours/day) or fluoxetine (20 mg/day). There were no significant differences in response between the two conditions.
The choice of treatment between light and medications should be individualized for each patient (Lam and Levitt, 1999). Some patients may need treatment with both antidepressants and light therapy.
Pathophysiology
