People with addictions often cannot quit on their own. Addiction is an illness that requires treatment. Treatment may include counseling, behavioral therapies, self-help groups or medical treatment. People often assume that those with addictions should be able to quit by simply making up their minds to do so. Addiction is thought to be possible for a wide range of chemical substances. Dependence, most often related to physical symptoms, can occur for a subset of the chemicals that cause addiction. For instance, an individual is prescribed a medication by a doctor for a legitimate reason (such as pain after an injury) and this can lead to physical withdrawal symptoms if this medication is stopped. Even more rarely, this post-medical treatment drug dependence can lead to drug abuse. People with drug abuse problems are individuals whose brain biochemistry has been altered by alcohol or drugs.