The neurotransmitters serotonin and dopamine send messages to the brain and the rest of the body. The altered brain chemistry essentially requires constant, repetitive exposure to the substance or action to function psychologically and physiologically. This chemical dependence leads to tolerance and withdrawal symptoms, two of the hallmarks of substance abuse addiction that most often require a professionally monitored alcohol and drug detox. Addiction is defined as obsessive thinking and compulsive need for drugs, alcohol, food, sex or anything despite the resulting negative consequences. Addiction includes the development of tolerance combined with withdrawal symptoms. In addition to tolerance, an addict or alcoholic will experience intense physical cravings for the drug and an emotional obsession to take alcohol or drugs regardless of the consequences.<\/p>\n