Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation in this study includes completion of a light intervention for 3,5 weeks (30 min each day) and 2 visits (1h) to the treating hospital pre- and post-intervention. The visits aim to provide instructions and equipment and to collect two blood samples. Additionally, 5 saliva samples will be collected by the participant at home pre- and post-intervention. Moreover, participants complete questionnaires (30 min, 4 times) and wear an accelerometer (10d, 4 times and during light therapy) to objectively measure sleep quality and activity. Risks of the light intervention are limited, although there are few known reports of agitation, headache and nausea during the first days of light exposure. Benefits are the use of an easy to administer treatment for one of the most distressing symptoms that participants report.