Withdrawal is an unpleasant state that occurs when someone who has been taking a drug regularly suddenly stops taking the drug. This can be a risky way to quit drugs or alcohol.
Withdrawal symptoms vary greatly, from being mildly unpleasant to life-threatening, and medical supervision and treatment -- detox -- can greatly improve safety, as well as the individual's experience of the physical effects and psychological symptoms. Withdrawal from a drug tends to be opposite to the effects of the drug.
Different drugs produce different withdrawal syndromes
Sometimes, withdrawal symptoms can go on for much longer than the initial detox period.