Does legalizing recreational marijuana in a state lead its residents to use it, or other substances, more? How does legalization impact careers, family life and mental health? Are some people more vulnerable to its negative impacts than others?
These are some of the questions University of Colorado researchers hope to help answer via a sweeping new $5.5-million study of 5,000 twins funded by the National Institute on Drug Abuse (NIDA). It is the first and only study of its kind in the nation.
“Increasing numbers of states are legalizing recreational marijuana, but we know almost nothing about the health and social consequences of this dramatic and rapid shift in public policy,” says John Hewitt, director of the Institute for Behavioral Genetics at CU Boulder and a co-principal investigator of the study. “There is clear need for solid scientific evidence, and the experiment now unfolding in Colorado provides a rare opportunity to accumulate such evidence.”
Results of marijuana legalization
For the study, Hewitt and co-principal investigator Christian Hopfer, MD, a professor of psychiatry at CU Anschutz Medical Campus, will collaborate with colleagues at the University of Minnesota to study 1,250 sets of twins ages 23 to 29 there, where recreational use remains prohibited, and 1,250 sets of twins in Colorado, where it has been legal since 2014.
As part of several ongoing longitudinal studies of twins, the researchers have already been following the participants for 15 to 20 years, collecting data on their use of marijuana, alcohol and other drugs in adolescence, as well as about their psychological health and social functioning. Via phone and internet surveys over five years, they’ll now collect data from the twins again looking at changes in behavior from prior to legalization to after legalization in the Colorado cohort.
By including twins living in Minnesota, the researchers can control