Study designs of evaluations included in the review
Placebo-controlled, randomised controlled trials (RCTs) were eligible for inclusion in the review.
Specific interventions included in the review
Studies that compared light therapy with a credible control were eligible for inclusion. Given the absence of standard definitions in the literature, the following inclusion criteria on dosing were applied:
in studies of bright light treatment for seasonal affective disorder (SAD), there had to be a minimum of 4 days of at least 3,000 lux-hours, with comparison groups receiving a maximum of 300 lux;
in studies of dawn simulation treatment, the intervention group needed to receive increasing light exposure from 0 to 200-300 lux over 1 to 2.5 hours, with comparison groups receiving an increase of less than 5 lux and/or less than 15 minutes in duration;
studies of bright light used as adjunctive treatment had to meet the same criteria as that for bright light treatment of SAD.
A variety of treatment doses was found amongst the included studies and their duration ranged from 6 to 42 days.
Participants included in the review
Studies of adults aged between 18 and 65 years in the acute phase of treatment for mood disorders (diagnosed using the American Psychiatric Association's DSM-III, DSM-III-R or DSM-IV criteria, the Research Diagnostic Criteria or the Rosenthal criteria) were eligible for inclusion. Subsyndromal diagnoses were excluded. The primary studies included patients with SAD and non-seasonal depression.
Outcomes assessed in the review
The primary outcomes of interest were psychiatric symptom measures such as the Hamilton Depression Rating and Seasonal Affective Disorders Version scores.
How were decisions on the relevance of primary studies made?
Two reviewers independently assessed the eligibility of studies for inclusion in the review. Eligible studies were then data extracted in detail prior to a final decision by the two reviewers on whether to include them. Any disagreements were resolved by consensus.