Hypersensitivity to Light in Delayed Sleep-Wake Phase Disorder

Delayed Sleep-Wake Phase Disorder (DSWPD) is characterized by significant delay in the major sleep period relative to desired sleep/wake times. Most patients also experience a delay in their internal clock (termed circadian DSWPD). In this thesis, I found that patients with circadian DSWPD are more sensitive to the phase-delaying effects of evening light. Patients with circadian DSWPD also experienced greater intra-individual variability in circadian and sleep timing than healthy controls. There were no differences in alerting effects of light. These findings demonstrate that light sensitivity is a core element of circadian DSWPD, which future behavioural interventions should target.