This study examined genetic and psychological factors found in a group of 50 individuals with DSM-IV cannabis dependence compared to a control group without a diagnosis of cannabis dependence.
The study found two factors appeared to increase the risk for cannabis dependence.
One factor was a genetic factor involving the proenkephalin gene. A second factor was high score on a psychological measure of neurosis. Neurosis is a psychological factor related to risk for a variety of anxiety conditions.
The study found a particularly elevated interaction risk for individuals who had both the high risk proenkephalin genotype as well as high scores on neuroticism. When both factors were present, risk for cannabis dependence was estimated to be about ten times higher compared to individuals without the high risk gene and with low neuroticism scores.
Legalization of marijuana in some states in the U.S. will provide a natural experiment to look at rates of problems with cannabis use. Although limited cannabis may be used without major complications in some individuals, others may find increased access leading to development of dependence and related social, medical and behavioral complications.
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