Of the over 22 million Americans who were classified with substance dependence or abuse in 2010, 2.9 million were dependent to or abused both alcohol and illicit drugs, 4.2 million had dependence or abuse of illicit drugs but not alcohol, and 15.0 million had dependence or abuse of alcohol but not illicit drugs.
Marijuana is produced in practically every region of the world, and is also the most produced illicit drug in the world.
The FDA has urged physicians to use great caution when prescribing methadone, because of the potential for respiratory distress and dangerous changes in an individual's heart beat that cannot be felt by the patient.
Use of amphetamines can cause an individual to behave in a bizarre, repetitive fashion and many become hostile and aggressive.