"i am a survivor of brain cancer and now have a memory deficit as a result. my neurologist suggested i take 100mgs of l-tryptophan daily to increase the production of serotonin. this he felt would assist with memory function. long story short, 2 years later, i realize that i have benefited from the side effect of sleepiness. i take my 1000 mg before i go to bed and i sleep like a log."