Evidence for Efficacy

Evidence for Efficacy

Acute-Phase Treatment

Because the recipient of light therapy is not "blind" to the treatment being administered, the development of a suitable control treatment for light therapy has been a problem since the earliest treatment studies were conducted. Despite this difficulty, dozens of controlled studies have been performed in which a treatment predicted by the investigators to be active was compared with a treatment predicted to be inactive. In many of these studies, differences between active and control treatments were found. Thus, more intense light sources have been shown to be superior to less intense ones; eye exposure has been shown to be superior to skin exposure (Wehr et al. 1987); and green light has been shown to be superior to red light (Oren et al. 1991). Two recent large-scale placebo-controlled trials have largely laid the efficacy question to rest. In one study of 158 patients with SAD (M. Terman et al. 1998), 30 minutes a day of morning 10,000-lux treatment beginning within 10 minutes of awakening proved robustly more effective than light at other times of day as well as placebo-controlled treatments. Another study of 96 subjects (Eastman et al. 1998) showed similar robust effects of morning light treatment compared with evening light treatment or placebo. These studies, together with the remaining literature, now provide strong evidence in favor of a specific antidepressant effect of light therapy in SAD. Morning light seems to provide the strongest treatment effects for SAD (Lewy et al. 1998), although evening light does provide a stronger treatment effect than placebo.

Although the conclusions described above are valid for light therapy administered with a light box, results of studies with a portable, head-mounted light visor are more difficult to interpret. In three multicenter studies of a light visor (Light Visor, Bio-Brite, Inc., Bethesda, MD) involving more than 200 patients, no difference in efficacy was observed at widely differing intensities (Joffe et al. 1993; Rosenthal 1993; Teicher et al. 1995). Response rates in these studies were comparable to those in some light box studies, but the absence of any differences between treatment conditions raises a problem in interpreting these findings. Although controlled studies are lacking, for those for whom portability is important for travel or mobility, a trial of a visor might be warranted.

Light Therapy Introduction Diagnostic Indications and Contraindications

• Indications
• Contraindications to Light Therapy Evidence for Efficacy