North America is in the midst of its most serious drug-overdose crisis in history. From 1999 through 2015, drug-overdose deaths approximately tripled in the United States, and the majority of such deaths now involve an opioid. In 2016 alone, there were 64,000 drug-overdose deaths in the United States — more than the total number of U.S. military deaths during the Vietnam War. As a result, and despite gains in other areas of medicine and public health, the United States recently experienced its first major decline in life expectancy since 1993.

To many, cannabis is a recreational drug; to some, it is a medicine. Now, it is increasingly seen as a crop, to be grown in quantity and engineered for better traits—not just pharmacological effects, but also fiber content and the rapid, efficient growth that makes a plant useful for biofuels. This month, in a special issue of Critical Reviews in Plant Sciences, researchers delve into all aspects of cannabis biology and ecology. The work sheds light on how the plant has diversified since it was first grown 8500 years ago in Eurasia.

Cannabis agriculture is a multi-billion dollar industry in the United States that is changing rapidly with policy liberalization. Anecdotal observations fuel speculation about associated environmental impacts, and there is an urgent need for systematic empirical research. An example from Humboldt County California, a principal cannabis-producing region, involved digitizing 4428 grow sites in 60 watersheds with Google Earth imagery. Grows were clustered, suggesting disproportionate impacts in ecologically important locales.

Despite evidence of substantial comorbidity between psychiatric disorders and substance involvement, the extent to which common genetic factors contribute to their co-occurrence remains understudied. In the current study, we tested for associations between polygenic risk for psychiatric disorders and substance involvement (i.e., ranging from ever-use to severe dependence) among 2573 non-Hispanic European–American participants from the Study of Addiction: Genetics and Environment.

Mental, neurological, and substance use (MNS) disorders are highly prevalent and are responsible for 14% of the global burden of disease expressed in disability-adjusted life years (DALYs). The resources that have been provided in countries to tackle the huge burden are insufficient, inequitably distributed, and inefficiently used, which results in a large majority of people with these disorders receiving no care at all. Even when available, treatment and care often is neither evidence-based nor of high quality.