An illicit drug is a drug that is illegal to have, and the non-medical use of drugs that are legally available. Illicit drugs include the misuse of prescription psychotherapeutics or the use of marijuana, cocaine (including crack), heroin, hallucinogens, inhalants, or methamphetamine. Illicit drugs represent the largest volume of criminal cases that are examined by forensic science laboratories. The use of illicit drugs can cause serious health risks, and some drugs can cause addiction after a single use. The United Nations Office on Drugs and Crime (UNODC) lists opioids, cocaine, cannabis, and amphetamines as the four different groups of illicit drugs. The misuse of prescription psychotherapeutics, such as pain relievers, tranquilizers, stimulants, and sedatives, is also considered illicit drug use.