Temple, Brown & Hine [1] make poignant critiques of the literature on cannabis use and misuse. Most of these would apply to other addictions research. In fact, all the sciences could benefit from reliable definitions, improved assessment of covariates, increased statistical power, consistent replications and better attention to the clinically meaningful. Their clarion call for more research is both necessary and appreciated. As these authors emphasize, we now have a vague sense of who is likely to use cannabis, some decent strategies for picking out the few who might develop problems with the plant, useful insights into what to do to help them tackle those problems and a few tips for preventing negative consequences in the first place. Nevertheless, a large elephant looms in the room with the grass ceiling. While we make important points about effect size and causality, those who perceive academics as living in an ivory tower of irrelevance can make an impressive case. It is true that we should continue our incremental steps towards better research. Our work is important; but in the meantime, cannabis and the laws associated with it are altering an astounding number of lives. The time for dispassionate academic discourse alone may have passed.

Hundreds of thousands of people are arrested world-wide for owning this green weed—the very one that we still do not understand particularly well. In the United States alone, enforcement officers make almost 850 000 cannabis arrests annually, more than 80% for possession [2]. Numbers this large are incomprehensible. If we bowed our heads in silence for 1 second for each arrest, we could lift them again 9 days later. That is more than 150 arrests for each word in the paper [1]. Every ‘and’, ‘it’ or ‘significance’ that they have written represents more than 150 cumbersome interactions with police, hundreds of hours spent booking and fingerprinting, valuable court time and countless amounts of cash. Those who grow enough cannabis are sentenced to longer prison terms than are murderers and rapists [3]. These negative consequences of cannabis laws dwarf any negative consequences of cannabis itself. Who would not prefer a cough or withdrawal to prison time? Perhaps we are focusing on the wrong problem.

All these arrests seem to be of little avail. Despite crackdowns, cannabis remains the most popular illicit drug on earth. Use rarely varies with penalties, sometimes suggesting that teenage consumption is lower where laws are less punitive [4]. As Temple and colleagues [1] explain, the idea that use is a meaningful measure is certainly debatable. The frequency of such use barely predicts problems, and troubles are infrequent compared to those created by most other psychoactive substances [5]. Nevertheless, prohibitions remain. Even those who care little for the arrested must confess: these laws tie researchers' hands. Reports of cannabis use are suspect, in part because of prohibition. In some countries, gaining approval to administer the plant can be a grueling, tedious process. In the United States only a single strain is available in limited strengths. Ironically, research participants often have stronger cannabis at home. Most have used varieties that create effects we cannot reproduce in controlled conditions with the cannabis available legally [6]. In this sense, although all the hindrances that Temple and colleagues mention are important [1], prohibition is part of why we know so little about cannabis.

So what are we supposed to do? We could all storm our governments demanding change. A simpler task might sound more reasonable. Nearly every published paper has obligatory parts to the discussion. We all know to harp on the limitations of our data before reviewers beat us to it. Even those of us who have never seen a client or run a program invariably tip our hats to implications for treatment and prevention. Perhaps cannabis researchers could add a line or two about policy to papers. A few words about what our data mean for the rationality of arresting people for owning a plant could be most welcome. These need not require larger leaps than the ones we make for prevention and treatment. The public is counting on us.

Declaration of interests

I am associated with organizations dedicated to reforming cannabis policy.