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 .
An attempt to prevent winter depression by light exposure at the end of September
Seasonal affective disorder ( SAD ) , winter type , is characterized by the occurrence of depression in autumn/winter , followed by a complete recovery in spring/summer . In SAD patients , some atyp- ical symptoms are highly characteristic , such as hypersomnia , carbohydrate craving , weight gain , fatigue , and loss of social inter- actions ( Rosenthal et ai 1984 ) . The repeated occurrence of symp- toms during successive winters is one of the diagnostic criteria , l ~ lot every SAD patient becomes depressed every year , however . In prospect i ve studies it was found that 70,4 % of the SAD diagnosed subjects who were followed from a symptom-free moment at the end of September , became depressed during the following winter ( Meesters et al 1991 ; 1993a ) , In a previous study it was found that severe winter depression can be prevented by light treatment administered at the first signs of an emerging winter depression , that is , the moment subjects reported complaints of slight depression ( Meesters et al 1991 ; 1993a ) . In the present study , the question was raised whether light exposure given at the beginning of the winter season , when sub- jeers are still free of symptoms , could be successful in preventing the development of a winter depressmn during the rest of the season . Such a ueatment , which might prevent depression alto- gether , would be highly advantageous
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 .