There is no absolute theory about what causes addiction. Some people argue "addiction is an inherited disease, and that the individual is permanently ill at a genetic level, even with those experiencing long periods of sobriety". Another theory is that "addiction is a dual problem consisting of a physical and mental dependency on chemicals, compounded by a pre-existing mental disorder (i.e. clinical depression, bipolar disorder, or some other mental illness), and that the mental disorder needs to be treated first as the primary cause of the addiction." (http://alcohol-drug-treatment.net/addiction_causes.html). .
Nicotine is one of the most heavily used addictive drugs in the United States. "In 1998, 60 million Americans were current cigarette smokers, 4.1 million were between the ages of 12 and 17." (http://www.nida.nih.gov/Infofax/tobacco.html). Nicotine is highly addictive. It is both a stimulant and a depressant to the central nervous system. The consumption of nicotine causes "a discharge of epinephrine from the adrenal cortex." This stimulates the central nervous system that causes a release of glucose. After stimulation depression and fatigue follow which leads the abuser to want more nicotine (http://www.nida.nih.gov/Infofax/tobacco.html). Daily users are exposed to the effects of nicotine for 24 hours each day. Research has shown that stress and anxiety affect nicotine dependence. The stress hormone "corticosterone" reduces the effects of nicotine; which means more nicotine must be consumed to achieve the same effect (Bender 87). Research has shown that nicotine, like cocaine, heroin, and marijuana, which are all addictive substances, increases the level of the neurotransmitter dopamine which means when this level of dopamine decreases a person would need more nicotine to get the same level of happiness.
"Cocaine is a powerfully addictive drug of abuse. Once having tried cocaine, an individual cannot predict or control the extent to which he or she will continue to use the drug.