Marijuana has been and remains to be the most common illicit drug used by Americans each year.
Most individuals with a history of chronic drug addiction are polydrug users (users of more than one drug) and will require drug rehab for all of the substances that they abuse.
Opiate addicted individuals commonly experience severe mood swings and noticeable changes in behavior and attitudes.
Proponents of methadone maintenance often state that patients receiving treatment are "dependent" on the medication, not "addicted".