A randomized, placebo-controlled trial of bright light and high-density negative air ions for treatment of Seasonal Affective Disorder
Introduction
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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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.
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Subjects
A total of 73 female students and staff at Hollins University in Roanoke, Virginia (latitude 37° 16′, North; average sunrise time ~ 0732 a.m.) participated in this study that was conducted each January over 5 consecutive years. The group included 67 White (90.5%) and 7 Black (9.5%) women, and subjects ranged in age from 18 to 51 years (M = 20.8 years; S.D. = 5.69 years). None had prior experience with either light or negative ion therapy.
A request for subjects was announced in campus media in
Ultraviolet and ozone measurements
Without the diffusing screens in place, ultraviolet radiation output at the fluorescent tube surface of the BWL box was less than 1% of the total output of the 10,000 lux light box and was not detectable from the surface of the DRL box tube surface. With diffusing screens in place, ultraviolet output measured at the screen was reduced to substantially less than 0.01% of the total BWL box output and was not detectable for the DRL box. Ultraviolet radiation measurements taken at distances of ≥
Discussion
Analyses of raw scale scores indicated that each treatment significantly reduced the symptoms of SAD and that treatment effects were equivalent for all four groups. These results corroborate those of Eastman et al. (1998) who found that bright light and an inert negative ion generator produced comparable reductions in SIGH-SAD scores but did not differ from each other and also agree with findings by Wileman et al. (2001) that bright light and dim red light both produced substantial and
Acknowledgments
This research was supported by Hollins University Faculty Research Grants and by a Paula P. Brownlee Professorship Research Grant. We thank Elizabeth Canyock, Leah McConoughey, and Catherine Bryan for assistance in data collection and also extend our appreciation to Michael Terman, Ph.D. and Richard Michalski, Ph.D. for their constructive and helpful comments.
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