What leads one person to depend on alcohol and another to shop compulsively?
Factors such as one's environment and one's genetic disposition can play a role, according to Wende Wood. For example, if one's parents are smokers, then exposure to role models who smoke can play a role in establishing this behavior as acceptable – and this lays the groundwork for taking the first cigarette. Not everyone who smokes becomes addicted – so there is a certain genetic disposition to the amount of "reward" that gets delivered to the brain – but without that first exposure to the substance, the reward pathway cannot be established and the habit does not develop. Of course, not all children of smokers become smokers themselves; some may as a result of their environment decide never to smoke.
Wood also explains that availability of the substance of abuse is key. While the Centre for Addiction and Mental Health does not support the gateway theory of drug use (that use of certain illicit drugs such as marijuana or ecstasy is a "gateway" to use of stronger drugs such as cocaine or crystal meth), Wood acknowledges that some illicit drugs are more widely available than others and therefore are often the first drug that a person might try. And over time, as tolerance to the drug builds up, other types of drugs may then be sought.
Sam Waldner agrees that availability plays a role in developing a compulsive behavior or abuse of a substance. He adds that peer involvement is also a factor. What different forms of addiction have in common, Waldner notes, is the same underlying issue: addictive disease. Thus, although a person may have a natural propensity towards one certain behavior (e.g., gambling) and may first manifest an addiction in that area, the disease tends to eventually spill over into other activities. In other words, a person with a gambling habit may eventually start abusing prescription drugs or alcohol.