Overall , both forms of preventive light therapy reduced the incidence of SAD numerically compared with no light therapy .
BACKGROUND Seasonal affective disorder ( SAD ) is a seasonal pattern of recurrent major depressive episodes that most commonly occurs during autumn or winter and remits in spring .
The prevalence of SAD ranges from 1.5 % to 9 % , depending on latitude .
The predictable seasonal aspect of SAD provides a promising opportunity for prevention .
This review - one of four review s on efficacy and safety of interventions to prevent SAD - focuses on light therapy as a preventive intervention .
Light therapy is a non-pharmacological treatment that exposes people to artificial light .
Mode of delivery ( e.g. visors , light boxes ) and form of light ( e.g. bright white light ) vary .
OBJECTIVES To assess the efficacy and safety of light therapy ( in comparison with no treatment , other types of light therapy , second-generation antidepressants , melatonin , agomelatine , psychological therapies , lifestyle interventions and negative ion generators ) in preventing SAD and improving patient-centred outcomes  among adults with a history of SAD .
Prophylactic treatment of seasonal affective disorder (SAD) by using light visors: bright white or infrared light?
BACKGROUND Thirty-eight patients with SAD participated in a light visor study addressing two questions . 1 . Can the development of a depressive episode be prevented by daily exposure to bright light started before symptom onset in early fall and continued throughout the winter ? 2 . Does the light have to be visible in order to have beneficial effects ? METHODS Three groups participated in the study : I ( n = 14 ) received bright white light ( 2500 lux ) ; II , ( n = 15 )  received infrared light ( 0.18 lux ) ; III ( n = 9 ,  control group ) did not receive any light treatment at all . RESULTS Infrared light is just as effective as bright white light . Both are more effective than the control condition . CONCLUSIONS Light visors can be effectively used to prevent the development of SAD . The fact that exposure to infrared light was as effective as exposure to bright white light questions the specific role of visible light in the treatment of SAD
Overall , both forms of preventive light therapy reduced the incidence of SAD numerically compared with no light therapy .
BACKGROUND Seasonal affective disorder ( SAD ) is a seasonal pattern of recurrent major depressive episodes that most commonly occurs during autumn or winter and remits in spring .
The prevalence of SAD ranges from 1.5 % to 9 % , depending on latitude .
The predictable seasonal aspect of SAD provides a promising opportunity for prevention .
This review - one of four review s on efficacy and safety of interventions to prevent SAD - focuses on light therapy as a preventive intervention .
Light therapy is a non-pharmacological treatment that exposes people to artificial light .
Mode of delivery ( e.g. visors , light boxes ) and form of light ( e.g. bright white light ) vary .
OBJECTIVES To assess the efficacy and safety of light therapy ( in comparison with no treatment , other types of light therapy , second-generation antidepressants , melatonin , agomelatine , psychological therapies , lifestyle interventions and negative ion generators ) in preventing SAD and improving patient-centred outcomes  among adults with a history of SAD .