All through the debate over marijuana legalization, a consistent complaint raised by opponents of such plans (frequently coming from more conservative critics) has been the idea that the health risks associated with using pot have been downplayed or overlooked entirely. There’s competing research showing that smoking pot is probably less harmful than smoking tobacco, but it’s a nagging question that’s never been entirely resolved.

Now the opponents of legalization may have another bit of ammunition in their arsenal. The results of a nearly ten-year study conducted in Great Britain were released this week and they suggest that regular consumption of newer, more powerful strains of cannabis can result in significantly higher instances of psychosis among users. Of course, as with all such studies, the warnings come with a few caveats. (Associated Press)

Smoking high-potency marijuana every day could increase the chances of developing psychosis by nearly five times, according to the biggest-ever study to examine the impact of pot on psychotic disorder rates.

The research adds to previous studies that have found links between marijuana and mental health problems, but still does not definitively pinpoint marijuana as the cause.

Psychotic disorders — in which people lose touch with reality — are typically triggered by factors including genetics and the environment. But experts say the new study’s findings have implications for jurisdictions legalizing marijuana, warning they should consider the potential impact on their mental health services.

Some of the figures they’re quoting from the study certainly do sound alarming. We’re not talking about some statistically insignificant increase in incidents of psychosis. From a pool of more than 2,000 patients, incidents of initial onset of psychosis were anywhere from three to five times higher among regular pot users as compared to the control group who didn’t partake.

But the study’s authors also include enough caveats to keep the debate going in the future. First, they admit that psychosis is generally understood to involve environmental and genetic factors, so quantifying exactly how big of a role the marijuana use played in each case is tricky.

Even if we ignore those questions, the quality and amount of pot you’d have to be indulging in to generate the worst results is a bit off the charts. To get the fivefold increase in psychosis diagnoses, the patients would have to be ingesting some of the really high potency, designer pot that growers have been developing, containing vastly higher levels of tetrahydrocannabinol (THC) than the stuff that was going around during the Summer of Love. (Or at least, so I’ve heard… [cough].) And even then, you’d have to be in the category of people who are “getting their smoke on” multiple times per day, seven days a week.

It sort of makes sense that you run a higher risk of problems from introducing any foreign agent into your system if you’re hitting it at Cheech and Chong levels as opposed to the person who only does it occasionally on the weekends. Another factor I didn’t see mentioned in the overview of the study results is whether they were including people who actually smoked marijuana as opposed to those using vaporizers, edibles or other forms of ingesting the drug. “Smoking” anything, including tobacco, involves bringing a lot more foreign substances into your system than just the specific drug you’re looking for, whether that’s THC or nicotine.

I don’t expect this one study to put the legalization issue to rest one way or the other. It’s just another interesting data point to keep in mind as we monitor the rollout of legalization laws around the country.