This study, conducted over the course of 5 years, assessed the antidepressant efficacy of two active treatments, bright white light and high-density negative ions, and the efficacy of two placebo treatments, dim red light and low-density negative ions, for Seasonal Affective Disorder (SAD). In a controlled laboratory setting, 73 women with SAD were exposed to one of the four treatment conditions over 12 consecutive days. Pretreatment expectation ratings did not significantly differ among the four treatment groups; however, expectation scores and treatment benefits were positively related. Over the course of treatment, subjects in all four groups showed significant score decreases on the Structured Interview Guide for the Hamilton Depression Rating Scale–Seasonal Affective Disorder Version–Self Rating (SIGH-SAD-SR) and on the Beck Depression Inventory (BDI). For raw scale scores, neither main effects of treatment nor interactions between treatment and time were significant. When remission outcome criteria were used, bright white light was significantly more effective than any of the other three treatments, and exposure to high-density negative ions was more effective than either of the two placebo conditions, although the difference was not significant.
Seasonal Affective Disorder (SAD) is a subtype of recurrent mood disorder with a characteristic pattern of onset and remission (American Psychiatric Association, 1994). Episodes of SAD predominantly occur in fall and winter and are characterized by typical symptoms of depression as well as atypical symptoms including excessive sleep with difficulty waking, craving for carbohydrates, weight gain, irritability, social withdrawal, daytime fatigue, and loss of concentration (Rosenthal et al., 1984a, Rosenthal et al., 1985, Tam et al., 1997, Thompson et al., 1999 and Partonen et al., 1998). The incidence of SAD is four times more prevalent in women than in men (Blazer et al., 1998) and is highest among individuals with a history of recurrent mood disorders (Lam and Levitt, 1999). Explanations of how SAD develops include delayed circadian rhythms (Lewy et al., 1988), irregularities in the level and/or regulation of specific neurotransmitters, and genetic factors (Madden et al., 1996 and Lam and Levitan, 2000).
Although antidepressant medications are effective in alleviating the symptoms of SAD (Ruhrmann et al., 1998, Kasper et al., 2001, Moscovitch et al., 2004 and Lam et al., 2006), bright light is also a viable treatment for individuals with this disorder (Terman et al., 1989, Terman and Terman, 1995, Tam et al., 1995, Wesson and Levitt, 1998 and Terman and Terman, 2005). Light therapy has relatively few side effects as compared to those of antidepressant medications (Labbate et al., 1994, Terman and Terman, 1999 and Terman and Terman, 2005). The superiority of light therapy over placebo treatments, however, remains equivocal. Whereas some investigations found light therapy to be more effective than dim or brief duration light control conditions for treating SAD (Rosenthal et al., 1984b and Terman and Terman, 2005), others reported little or no difference in antidepressant response between bright light and an inert photic placebo treatment (Levitt et al., 1996 and Wileman et al., 2001). For example, Eastman et al. (1992) reported that treatment with either a deactivated ion generator or bright light produced significant and equivalent reductions of depression ratings in patients with SAD. Exposure to high levels of negative air ions is also an effective treatment for both the depressive and atypical symptoms of SAD (Terman and Terman, 1995, Terman and Terman, 2006 and Terman et al., 1998). More broadly, exposure to high levels of negative ions increases relaxation and mental alertness, decreases irritability and tension, enhances motor performance and energy level, and alleviates depressed mood (Charry and Hawkinshire, 1981, Tom et al., 1981, Buckalew and Rizzuto, 1982, Yates et al., 1986, Baron, 1987 and Nakane et al., 2002). Exposure to high concentrations of positive air ions, in contrast, typically produces opposite effects including tension, irritability, depression, insomnia, social withdrawal, and reduced motor performance (Krueger and Reed, 1976 and Charry, 1987).
Previous research suggests that bright light and high-density negative ions are generally more effective than either photic or nonphotic control conditions, but not both (Eastman et al., 1998 and Terman et al., 1998). To assess the effectiveness of bright light as compared with that of high-density negative ions for treating SAD and to further evaluate the degree to which placebo expectancies contribute to the effects of these treatments, the present study utilized a parallel-group design to evaluate the efficacy of both treatments not only relative to each other but also relative to dim red light and to low-density negative ions. Unlike previous studies in which subjects self-administered treatments in their places of residence, this study required that all subjects received treatments in a controlled laboratory setting.
We predicted that exposure to bright white light or to high-density negative ions would produce comparable reductions in the depressive and atypical neurovegetative symptoms of SAD and that the efficacy of either of these treatments would be superior to that of dim red light or of low-density negative ions.
