There are four major categories of drugs: hallucinogens, stimulants, opiate narcotics, and sedative-hypnotics. The relationship between drugs and crime can be viewed as crimes related to the use, sale, and possession of illegal drugs, and how certain drugs can pharmacologically influence criminal behavior. Research has found that drug use is common among arrestees and inmates, and that some offenders commit crimes to support drug habits, while drug trafficking engenders other violent crimes.