Cancer related fatigue (CRF) is one of the most prevalent and distressing long-term complaints reported by (non-) Hodgkin survivors. The SPARKLE study will test the efficacy of two intensities of light therapy on cancer related fatigue. Additionally, it explores possible working mechanisms of light therapy on CRF including improvements in sleep quality, psychosocial variables (depression, anxiety, cognitive complaints, and quality of life), and changes in biological circadian rhythms.