In a propensity score-matched cross-sectional study of 684 children, outpatient melatonin use was not found to be associated with significant changes in total sleep time, non-REM sleep stages, respiratory parameters, arousal patterns, or periodic limb movements. Although a small reduction in REM sleep percentage was observed, but this association weakened after accounting for psychiatric diagnoses, suggesting possible residual confounding. Therefore, prospective studies are needed to determine whether melatonin directly influences REM sleep. The primary prespecified outcome was percentage of REM sleep, and 14 other PSG variables were analyzed using Benjamini-Hochberg FDR correction. The negative correlation with REM sleep remained significant even after varying the number of non-users.