Sleep stage diagrams and time and time-course change in waveform parameters measured during zolpidem abuse (A) and after addiction treatment (B). Under taking zolpidem high dose, elongation of the REM latency, poor slow-wave sleep and frequent nocturnal arousals were observed. N1–N3 = non-rapid eye movement stage 1–3 sleep, PSG = polysomnography, R = rapid eye movement sleep, REML = rapid eye movement sleep latency, SE = sleep efficiency, SL = sleep latency, TIB = time in bed, TST = total sleep time, W = wake, WASO = wake after sleep onset.