A newly published genome-wide analysis of more than 14,000 individuals has identified several gene variants that increase risk of cannabis dependence. The analysis also suggests that the genetic risk for dependence on marijuana is associated with a higher inherited risk of major depression.
The new study is published in the journal JAMA Psychiatry.
The study was first to identify variants that significantly increase risk for cannabis dependence. It was based on knowledge that, like alcoholism and other addictions, the risk of cannabis dependence can be inherited. The researchers wondered whether those with some forms of mental illness might also be at higher risk of cannabis dependence, as they are for addiction to other abused substances such as alcohol.
“We were surprised to find a genetic risk overlap between cannabis dependence and major depression,” said Dr. Joel Gelernter, the Foundations Fund Professor of Psychiatry, professor of genetics and of neuroscience, and senior author of the study.
Gelernter said the findings might also explain why those with schizophrenia are often diagnosed with cannabis dependence.
The analysis compared variations in the genomes of individuals who met the medical criteria for cannabis dependence with those of marijuana users who showed little or no signs of dependence. Some of the gene variants that predicted dependence are related to regulation of calcium levels aiding in the firing of neurons and in central nervous system development.
Richard Sherva of Boston University is first author of the paper.
Primary funding for the study was provided by the National Institutes of Health.
Publication: Richard Sherva, et al., “Genome-wide Association Study of Cannabis Dependence Severity, Novel Risk Variants, and Shared Genetic Risks,” JAMA Psychiatry, 2016; doi:10.1001/jamapsychiatry.2016.0036