The change in attitudes toward cannabis and in legal access to marijuana around the US over the past several years is staggering.
As of last fall, 57% of adults in the US said they thought marijuana should be legal, with only 37% taking the opposing view — which is essentially a reversal of the opinions held a decade ago.
And after November's elections, 20% of Americans live in a state that has voted to legalize recreational use. Far more live in states with some access to medical marijuana.
But this obscures a crucial fact: From a scientific perspective, there's still a ton we don't know about cannabis.
A massive report released today by the National Academies of Sciences, Engineering, and Medicine gives one of the most comprehensive looks — and certainly the most up-to-date — at exactly what we know about the science of cannabis. The committee behind the report, representing top universities around the country, considered more than 10,000 studies for its analysis, from which it was able to draw nearly 100 conclusions.
In large part, the report reveals how much we still have to learn, but it's still surprising to see how much we know about certain health effects of cannabis.
This summation was sorely needed, as is more research on the topic.
"The policy has outpaced science, and it's really too bad," Staci Gruber, an associate professor of psychiatry at Harvard Medical School and director of the Marijuana Investigations for Neuroscientific Discovery program at McLean Hospital, told Business Insider in an interview last week, several days before we saw the report.
"As a scientist, I think the goal is always to try very hard to get to the findings and to be able to disseminate those findings so that we can make good decisions grounded in science," Gruber said. Cannabis "has been around for thousands of years; it's not like we just made it in a lab."
Having good research is essential so that we know "how best we can use it, what are the safest ways, and what are the real risks," she added.
Surprising findings on cancer, mental health, and more
Before we dive into the findings, there are two quick things to keep in mind.
First, the language in the report is designed to say exactly how much we know — and don't know — about a certain effect. Terms like "conclusive evidence" mean we have enough data to make a firm conclusion; terms like "limited evidence" mean there's still significant uncertainty, even if there are good studies supporting an idea; and different degrees of certainty fall between these levels. For many things, there's still insufficient data to really say anything positive or negative about cannabis.