Unique provision in the American Recovery and Reinvestment Act prevented approval of second year no-cost-extension in which completion of analyses were planned.

This research project consists of a three part study with five embedded sub studies. The first study phase identifies "body rhythms" of sleepiness/wakefulness and of melatonin levels for each subject (including sub-study 1). The second study phase identifies the optimum dose and timing of melatonin for regulating each individual's 24-hour sleep/waking cycle (including sub-study 2). The third study phase introduces a new independent variable, light (including sub-studies 3 and 4). Sub-study 5 is an optional longitudinal study.

Sub-study 1 looks at how keeping a regular sleep schedule affects the body's natural rhythm. Sub-study 2 looks at how individuals metabolize melatonin. Sub-study 3 tests how individuals' endogenous melatonin production responds to bright outdoor light and Sub-study 4 tests a previous finding that artificial bright light exposed daily behind the knee can regulate the body clock. Sub-study 5 is an optional longitudinal study, an extension of the first study stage, for subjects whose rhythms are not clearly free-running.

Inclusion criteria:

• blindness for at least one year, verified by an ophthalmologic exam
• ability to comply with the requirements of the experimental protocol
• competency to sign informed consent

Exclusion criteria (as determined by medical history and/or physical examination):

• abnormal heart, liver or kidney function
• a current Axis I psychiatric or substance abuse disorder according to the DSM-IV Manual
• possibly external demands that limit the ability to maintain a regular schedule (e.g., night shift work)
• sexually active female subjects of child-bearing potential will be asked to avoid pregnancy using accepted methods and will be notified that the effects of melatonin on a fetus are not known (we will ask subjects monthly if they are pregnant or trying to become pregnant)
• if a subject reports she is pregnant or is trying to become pregnant anytime during her study participation, any study medications (melatonin or placebo) will be immediately withdrawn and the subject will be excluded from the study

The PI has retired from the institution. Sincere efforts were made to contact the PI/study team members, but were unsuccessful. No study data are available.

The PI has retired from the institution. Sincere efforts were made to contact the PI/study team members, but were unsuccessful. No study data are available.

Analyses were not completed because a unique provision in the American Recovery and Reinvestment Act (ARRA) of 2009 funding source unexpectedly prevented approval of a second year no-cost-extension in which completion of analyses were planned.