“…However, other studies show that early changes of REM sleep parameters, especially REM latency and percentage amount of REM during the sleep period time, might predict treatment outcome with substances, which have an accute effect on REM sleep like amitriptyline (Kupfer et al, 1981;Gillin et al, 1978) and clomipramine (Höchli et al, 1986). Furthermore, changes in REM sleep, especially REM density, occur in the course of antidepressive treatment with fluoxetine (Buysse et al, 1999a) leading to an increase in REM density, whereas under nonpharmacological treatment (Thase et al, 1994;Buysse et al, 1999a) REM density decreases. In drug-free depressed patients, an increased REM density is a state marker of depression (Lauer et al, 1991).…”