Pupillometry in Delayed Sleep Wake Phase Disorder

The goal of this observational study is to characterize the pupil light response in patients with delayed sleep-wake phase disorder. A subset of participants will take part in a clinical trial to determine if increasing serotonin can alter the circadian response to light. The main questions it aims to answer is: Are there differences in the light response in patients with delayed sleep-wake phase disorder? Does citalopram increase melatonin suppression in patients with delayed sleep-wake phase disorder? Participants will complete activity and melatonin testing at home to determine their circadian timing. This will be followed by an eye test looking at the pupil response to different light stimuli. A subset of participants will complete two inpatient admissions where melatonin levels will be sampled and they will be exposed to a bright light. During one round of testing they will receive a placebo and in the other round of testing they will take a single dose of citalopram, a selective serotonin reuptake inhibitor.

NCT Number	NCT06949644
Lead Sponsor	Northwestern University Collaborators: National Heart, Lung, and Blood Institute (NHLBI)
Conditions	Delayed Sleep-Wake Phase Disorder
Enrollment	220 participants
Start Date	2025-09-01
Primary Completion	2029-07-31 (estimated)
Study Completion	2029-08-31 (estimated)
Updated on ClinicalTrials.gov	2026-06-08