A pilot study of adherence with light treatment for seasonal affective disorder

Non-adherence with antidepressant medication regimens is now recognised as a substantial problem when evaluating depression outcome. Given the behavioural demands of light treatment (LT), it might be expected that non-adherence would be even more pronounced in LT, a form of intervention for seasonal affective disorder (SAD). However, little research has focused upon the extent to which patients in light treatment protocols adhere to set regimens. Nineteen patients with SAD were allocated to either treatment with bright white light (intervention) or dim red light (control condition) in a four-week protocol. Light exposure was estimated automatically (without participants' knowledge) with elapsed time meters built into the light box. Daily diaries were also used to measure self-reported light box use. Participants were instructed to use the light box for 30 min each day during week 1, 45 during week 2 and one hour during weeks 3 and 4 (total duration of prescribed light exposure 1365 min). The results indicated that mean duration of light box operation for the entire sample was 59.3% of the prescribed 1365 min. Six of nineteen (31.6%) patients dropped out of treatment. Amongst those completing treatment, adherence to the prescribed duration of exposure averaged 83.3% (S.D.=31.4). A trend was found for the intervention condition to generate a lower dropout rate, as well as a trend for the degree of adherence to be greater in the intervention condition. Importantly, there was no association between adherence as measured automatically and the higher rates of self-reported adherence as measured in diaries. In summary, the results of this pilot study suggest that adherence with light treatment is of a similar order of magnitude to antidepressant medication adherence. Patient self-report was found to be unrelated to objectively estimated duration of light box use, a finding with significant research and clinical implications. Future research studies should routinely measure and evaluate adherence with light therapy and evidence-based techniques for maximising treatment adherence should be incorporated into routine clinical practice.