I was a member of the military for 42 years from 1965 - 2008 and took the drug repeatedly without any side effects.  Cyprus for seven months in 1981, while in India for one year in 1987/88, seven months in RWANDA in 1995 and in Bosnia for six months in 2004.  It does I am sure affect different people in different ways but it certainly was better than the only alternative at the time - chance of getting malaria!  I do not believe it should have been optional then or until a suitable alternative was developed.  That said those that it did effect should be taken care of.