What is the effect of exogenous melatonin on sleep latency, sleep efficiency, and REM latency in healthy people?
Twenty-one studies were relevant to this question of the review. The quality of these studies was assessed using the Downs and Black Checklist.115 The overall quality of studies ranged from 11 to 25 on a 29-point scale; most studies had a score between 16 and 20; four studies had a score between 10 and 15;78 123–125 and one study had a score of 25.126 The quality of reporting ranged from 4 to 11 on an 11-point scale; most studies had a score between seven and nine, three studies had a score between four and six78 124 125 and two studies had a score of 10 or 11.126 127 The external validity of studies ranged from zero to three on a three-point scale; most studies had a score of zero, five studies had a score of one124 127–130 and one study had a score of three.126 The internal validity of studies ranged from seven to 11 on a 13-point scale; approximately half of the studies had a score of 10 or 11; five studies had a score of nine;78 127 131–133 and six studies had a score of seven or e
