Withdrawal is the body's reaction to abstaining from a substance upon which a person has developed a dependence syndrome. When dependence has developed, cessation of substance-use produces an unpleasant state, which promotes continued drug use through negative reinforcement; i.e., the drug is used to escape or avoid re-entering the associated withdrawal state. The withdrawal state may include physical-somatic symptoms (physical dependence), emotional-motivational symptoms (psychological dependence), or both. Chemical and hormonal imbalances may arise if the substance is not re-introduced. Psychological stress may also result if the substance is not re-introduced.[citation needed] Infants also suffer from substance withdrawal, known as Neonatal Abstinence Syndrome (NAS), which can have severe and life-threatening effects. Addiction to drugs and alcohol in expectant mothers not only causes NAS, but also an array of other issues which can continually affect the infant throughout his/her lifetime.[13]

This is an ongoing debate in the medical community, but it is generally agreed that there is no one cause for the development of addiction. According to the National Institute on Drug Abuse, contributing factors may include a genetic predisposition to develop addictive tendencies, an environment that is permissive of drug abuse, access to illicit substances, and certain developmental issues. The existence of a Dual Diagnosis is one of the biggest risk factors for the development of addiction. Heroin Withdrawal | First Week In