In the 1990s, Dr. Jack E. Henningfield of the National Institute on Drug Abuse and also Dr. Neal L. Benowitz of the College of The Golden State at San Francisco each ranked the 6 most habit forming medications. Mistreating this class of drugs can cause serious illness, including dependency as well as overdose. Indications of barbiturate overdose include clammy skin, dilated pupils, shallow breathing as well as coma.