Is the delayed sleep phase syndrome a physical or psychological disease? A case report of disappearance following a change of latitude

The delayed sleep phase syndrome is characterized by an abnormally late sleeping and arousal time. Among several available treatments, chronotherapy, light therapy and melatonin administration strongly suggest a frequently recurring disturbance of the brain's circadian clock. However, several studies show psychological disturbances, which are either potentially a consequence or a cause or only fortuitously associated. The first case of disappearance of the disturbance after a move to a tropical latitude does not determine the main responsible factor.