What is the study is about?

Legalizing recreational marijuana use in Colorado may affect public health, either positively or negatively, but it is unknown how substance use patterns will change with legalization and what other effects this will have.

Through interviews with participants who we have been in contact with for the past 15 years, we will be examining the impact of recreational marijuana legalization on the patterns of marijuana and other drug use, as well as other aspects of wellbeing and functioning at home and at work.

By conducting parallel studies in Colorado (with legalized recreational marijuana) and Minnesota (a non-legal State), where we have detailed prior longitudinal data on our participants, our new assessments in about 5000 adult twins across the two States will provide unique and powerful data to understand the impact of recreational marijuana legalization.

We anticipate that the effects of recreational marijuana legalization are unlikely to be uniform across the population. Rather, some individuals will be at higher risk to suffer negative consequences while other will be resilient, unaffected, or may see benefits. By building on the longitudinal and twin structure of the study, we will be able to determine the influence of individual differences that pre-dated legalization.

Who is paying for the study?

The funding for this project comes from the National Institute of Health in the form of a project grant awarded to Dr. Christian Hopfer at the Anschutz Medical Campus, in collaboration with the Institute for Behavioral Genetics (IBG) at the University of Colorado Boulder and to the Department of Psychology at the University of Minnesota. The project will run until 2022.

What does the study involve?

Participants in the study will be recruited from twin pairs who have previously taken part in our surveys. You should expect to take part in an initial interview on the telephone for about an hour, and fill out an on-line questionnaire. You will get $100 compensation for completing the initial interview and questionnaire. A year later you will fill out another on-line questionnaire, earning a further $50 compensation. However, the real value of participation in the study comes from the important new knowledge about real people’s behavior that will inform public understanding and policy.

What is unique about this study?

Projects like these are possible because of the cooperation of our twin study participants over many years from when they were children and adolescents to now when they are adults. What is different from most epidemiological studies, even when they are longitudinal, is that, by studying pairs of twins, we can also learn about the role of genetics in shaping our behavior and responses to major cultural changes like marijuana legalization. We expect individuals to differ in their response to this cultural change, and we hope to learn a bit more about why that is.