REM sleep latency is the interval between onset of any stage of sleep and onset of first REM sleep stage. Normal REM Sleep latency is <120 minutes. Sleep Onset REM (SOREM) is also abnormal. A short REM latency time may result from narcolepsy, sleep apnea, and depression or withdrawal from tricyclic anti-depressants (TCAs), Monoamine Oxidase Inhibitor (MAOI) medications, amphetamines, barbiturates and alcohol. Long REM latency may happen due to Sleep apnea , periodic limb movement of sleep and use of REM-suppressing medications, including TCAs, MAOIs, amphetamine, barbiturates, and alcohol.