Marijuana use and policy: what we know and have yet to learn.

• Author: Pacula, Rosalie Liccardo
• Position: Research Summaries

Marijuana is the most widely used illicit drug, with over 25 million individuals in 2003 estimated to have used marijuana in the past year. (1) Although prevalence rates for the general population have been relatively stable over the past decade, the proportion of current users who meet criteria established by the American Psychiatric Association for dependence or abuse of marijuana has increased at a statistically significant rate, from 30.2 percent to 35.6 percent. (2) In addition, prevalence rates among youth rose considerably during the mid-1990s before stabilizing, while perceptions of harms declined. (3) At the same time the United States has experienced a rise in youth use rates and dependence, there has also been a significant rise in arrests. (4) There is increasing pressure on many state legislatures to soften their policies toward marijuana as a way of reducing the criminal justice burden, and despite virtually no information available on the economic cost of marijuana use or abuse, there is growing support to do so.

Indeed, during the 1990s several states reduced the penalties or criminal status of first-time marijuana possession offences involving small quantifies of marijuana and some other states enacted legislation that gave patients protection from prosecution m state courts if they used or grew marijuana for medicinal purposes. (5) Whether changes in policies such as these would generate a cost savings for state governments depends on a number of different factors, including changes in enforcement that might have occurred in response to these policy changes, changes in use, and increases in the harmful consequences associated with use and abuse. Only the latter two associations have been carefully considered in recent empirical analyses in the United States and significant limits exist in drawing conclusions from them. Nonetheless, some important insights have been gained that are relevant for anyone interested in discussing marijuana policy. This research summary provides a review of what we currently know about marijuana use and identifies some gaps that need to be explored before a careful assessment of current marijuana policies can be conducted.

Price Matters

It is well established from national survey data that marijuana initiation generally occurs among youth in their mid-to-late teens and that regular use persists into the early twenties, and then steadily declines through the mid-to-late twenties and into the thirties. (6) Thus, if one is interested in understanding factors determining the initiation and escalation of marijuana use, it is important to examine youth populations. And, as one recent study points out, it is also important to understand that factors that are important correlates with contemporaneous demand may not be all that important for predicting trends in use rates over time. In a comprehensive assessment of the annual and 30-day prevalence of marijuana among high school seniors, my co-authors and I show that many of the key contemporaneous correlates with marijuana use (race, gender, and religiosity for example) could not explain the trend in use rates observed during the 1980s and 1990s. (7) Instead, the two most important predictive factors for explaining variation in both contemporaneous use rates and trends over time were attitudes about marijuana (perceived...