"i&#039;m 16. i was prescribed 36mg comcentra  i took it at 8:30pm (was suppose to take it in morning) it worksd it helped me focus but 3 hours into it i started feeling anxiety and later i had a crash. couldn&#039;t sleep stayed up the whole entire night. i also has many other side effects like lack of appitite and heavy breathing might be to large of a dose but overall without the crazy side effects it helped me get stuff done and concentrate"