Often antidepressants, such as SSRIs are used, not just for depression or anxiety, but because these drugs like Prozac Paxil, Sotralapram, also have the ability to treat cataplexy that sudden loss of muscle movement. In addition, they suppress REM sleep. And what we know is that REM sleep is exaggerated and in too much quantity in patients with narcolepsy and sometimes REM sleep can even sneak through during wakeful hours and cause some of that cataplexy or cause some of the sleep attacks that occur during the day. it used to be that we use tricyclic antidepressants for this purpose, but the newer drugs, the SSRI also do the same with fewer side effects.