How effective is light therapy for SAD ?
Several qualitative reviews have concluded that light therapy is an effective treatment for SAD, with response rates of 60% to 90% in controlled studies (Eastman et al 1998; Lamberg, 1998; Partonen & Lonnqvist, 1996; Tam et al, 1996).It has been found that between 75-85% of people suffering from SAD and SSAD feel better after 3-4 days of consistent light therapy. Some individuals feel better immediately after their first dose, even within 20 minutes of exposure, while others may need several days (Terman et al, 1998). Two meta-analyses also confirm the efficacy of light therapy against plausible placebo controls (Terman et al, 1989; Lee & Chan, 1999). In a longitudinal study of light therapy patients Graw et al 1997 found that over a number of years, the clinical diagnosis changed for the better in 64% of the patients, and that light therapy reduced the incidence and depth of subsequent depressive episodes.
Further evidence for this was the large reduction in use of conventional antidepressant drugs during the follow-up period. Sumaya et al (2001) found bright light treatment to be effective in the non-pharmacological treatment of depression among institutionalised older adults. Ibatoullina et al (1997) Presents a case report of a woman (46) with seasonal affective disorder without the typical depressed mood or lack of drive. The patient was given bright light therapy, and after 2 weeks of treatment, reported that her complaints had disappeared.
The authors suggest that this case gives preliminary evidence that, even in the absence of depressive symptomology, patients can present with distinct atypical symptoms which may respond well to bright light therapy.
Light therapy has been also found to be superior to conventional anti-depressants in the treatment of SAD, Ruhrmann et al (1998) investigated whether fluoxetine (Prozac™) has antidepressant effects comparable to bright light in the treatment of seasonal affective disorder and concluded that the remission rate in those patients using light therapy were far superior.
