At the time of this report's release in January 2017, 28 states and the District of Columbia have legalized cannabis for the treatment of medical conditions. Eight of these states and the District of Columbia have also legalized cannabis for recreational use. In addition to the growing availability of legalized cannabis, there has also been a rapid expansion in the types of available cannabis products, including edibles, oils, and a variety of inhaled substances. The growing acceptance, accessibility, and use of cannabis raise important public health concerns, and there is a clear need to establish what is known and what needs to be known about the health effects of cannabis use.

The committee was tasked with conducting a comprehensive review of the current evidence regarding the health effects of using cannabis and cannabis-derived products. The study was conducted in a limited time frame in order to respond to a quickly moving landscape, but as described in the report's methods section, the amount of work that this report entailed and the volume of literature reviewed clearly indicates the substantial effort involved and the importance of this issue to the committee.

In the current report, the committee presents a rigorous and thoughtful summary of the landscape of cannabis and health and puts forth recommendations to help advance the research field and better inform public health decisions. I wish to express my deepest gratitude to my fellow committee members who worked so hard and with good grace to accomplish this task. As with other National Academies of Sciences, Engineering, and Medicine reports, the work of the committee would have been far more difficult, if not impossible, without the support of a dedicated, knowledgeable, and very hardworking National Academies staff.

Marie C. McCormick, Chair

Committee on the Health Effects of Marijuana: An Evidence Review and Research Agenda