What are risk factors for addiction?

Studies of twins and of families that are prone to addiction suggest that about 50% of the risk for drug addiction is genetically based. The genetic ties to behavioral expressions of addiction have not been studied as thoroughly, but there is evidence that genes play a similar role in gambling disorders. A few reports even hint at a genetic link to compulsive shopping. More importantly, experts in the field propose that there is a genetic "load" or constellation of genes that predisposes people to addiction, but not necessarily to a specific type of addiction. In other words, the same genes that drive substance dependence might also drive compulsive shopping and compulsive gambling.

The environment in which people grow up and their personal histories also affect how likely they are to develop addiction. People who were abused or neglected as children, for example, have a higher risk of developing addiction than people who were nurtured as children. Similarly, people who have gone through traumatic events, such as rape or a natural disaster, are more prone to addiction than those who have been spared trauma.

People with mental illness also seem to be particularly vulnerable to addiction, and addiction and mental illness often overlap. By some estimates, as many as 65% of people who have drug addiction also have a mental illness such as depression, anxiety, or a personality disorder. Many experts believe that untreated mental illness may lead people to self-medicate with substances to ease their suffering.