Cannabis has never had anything to fear from science. There are several thousand studies showing the safety and efficacy of the plant as it pertains to medicine or personal use either one, and there have been few studies when subjected to replication and peer-review, that show any of the negatives of Cannabis use.
Nothing on this planet is perfect, but Cannabis comes as close to perfection as well as anything else.
To get an idea of studies available, go to https://grannystormcrowslist.wordpress.com/. This is up-to-date as of January of 2017, and they do periodic updates.
Yet, there are important things we don’t have hard and fast science on just yet. And that is getting people arrested for driving under the “Influence” of Cannabis, known here in Indiana as “Driving Under the Influence of Drugs” (DUID), based on the presence of any trace amount of Cannabis in the urine or blood. The psychoactive effects of Cannabis wear off within about four hours, depending on the quality and amount taken as well as individual physiology. However, non-psychoactive by-products (metabolites) of Cannabis can stay in the body for weeks or months. A lot of people, even in legal states, have been wrongly charged and convicted of DUID when they weren’t “Impaired” at the moment.
The problem is that there is no reliable way to actually determine one’s current state of psychoactivity on Cannabis, and most legislatures don’t want drivers impaired on anything. As of right now, there is no way to tell, no way to draw a line to guarantee public safety.
Bear in mind that every properly done, peer-reviewed and replicated study on Cannabis and driving shows “Stoned” drivers are insignificantly more impaired than “Straight” drivers. Officials need a cutoff point.
They may get that soon, and from an unlikely team of investigators. If successful, at least innocent people will not be charged with driving “Under the influence.”