Loss of response to melatonin treatment is associated with slow melatonin metabolism.

Background In some of our patients with intellec- tual disability (ID) and sleep problems, the initial good response to melatonin disappeared within a few weeks after starting treatment, while the good response returned only after considerable dose reduction. The cause for this loss of response to melatonin is yet unknown. We hypothesise that this loss of response is associated with slow melatonin metabolism. Method In this study, we determined melatonin