Light therapy for preventing seasonal affective disorder

Area of Science:

• Psychiatry
• Preventive Medicine
• Chronobiology

Background:

• Seasonal Affective Disorder (SAD) is a recurrent pattern of major depressive episodes linked to seasons, typically occurring in autumn/winter.
• SAD prevalence varies with latitude, ranging from 1.5% to 9%.
• The predictable seasonality of SAD presents an opportunity for preventive interventions.

Purpose of the Study:

• To evaluate the efficacy and safety of light therapy in preventing SAD among adults with a history of the condition.
• To compare light therapy against various interventions including no treatment, other light therapies, antidepressants, and psychological therapies.

Main Methods:

• A comprehensive literature search was conducted across multiple databases (EMBASE, MEDLINE, PsycINFO, CENTRAL, CINAHL, Web of Knowledge, AMED) up to August 2015.
• Included were randomized controlled trials (RCTs) of adults with a history of winter-type SAD, free of symptoms at baseline.
• One RCT with 46 participants, comparing bright white light, infrared light, and no light treatment, met the eligibility criteria.

Main Results:

• The single included RCT had significant methodological limitations, including high risk of bias and a small sample size.
• Both bright white light and infrared light numerically reduced SAD incidence compared to no treatment.
• Evidence quality was rated as very low due to study limitations, imprecision, and lack of reported adverse events or comparisons with other interventions.

Conclusions:

• The current evidence base for light therapy as a preventive treatment for SAD is very limited.
• Methodological weaknesses and small sample sizes in existing studies prevent definitive conclusions on light therapy's effectiveness.
• Patient preferences are crucial in deciding on SAD prevention strategies due to the scarcity of comparative evidence.