Why Are The Effects Of Marijuana So Unpredictable?

It’s long been known that different strains of the drug contain various amounts of Tetrahydrocannabinol (THC), the main psychoactive ingredient. When people talk about the effects of the drug – such as giddiness, the munchies and a sudden desire to watch The Big Lebowski – they’re typically referring to the effects of THC. (Interestingly, the same chemical can also make us paranoid. More on that later.) But THC doesn’t work alone – marijuana also contains cannabidiol, a compound associated with calm and relaxation. The ratio of THC to cannabidiol seems to be the key variable: Skunk-type strains, for instance, contain a higher ratio of THC to cannabidiol than, say, hashish. (According to a paper in Neuropsychopharmacology, “Delta-9-THC and CBD can have opposite effects on regional brain function, which may underlie their different symptomatic and behavioural effects, and CBD’s ability to block the psychotogenic effects of delta-9-THC.”) In general, high levels of THC seem to be desired by marijuana users, which helps explain why levels of THC have increased dramatically in the last few decades.

Now for the bad news: These popular skunk-strains (high in THC, low in cannabidiol) seem to be uniquely associated with memory loss. That at least is the lesson of a recent paper in the British Journal of Psychiatry.

The subjects were divided into groups of high (samples containing more than 0.75% cannabidiol) and low (less than 0.14%) cannabidiol exposure, and the data were filtered so that their THC levels were constant. Analysis showed that participants who had smoked cannabis low in cannabidiol were significantly worse at recalling text than they were when not intoxicated. Those who smoked cannabis high in cannabidiol showed no such impairment.

The larger message is that it’s very difficult to generalise about the effects of most drugs. Just look at marijuana: One of the recurring mysteries of the drug is why the same compound can both relax us and make us paranoid; it sometimes causes uncontrollable laughter and sometimes leads to runaway anxiety. This suggests that the context of use – our mental state when smoking a joint, or eating a pot brownie – can profoundly influence the outcome. While it remains mostly unclear how or why this happens, there’s some interesting new research on endocannabinoids in rough-skinned newts. (Endocannabinoids are a class of neuromodulators widely expressed in the brain. Their name gives away the punchline: THC binds to endocannabinoid receptors with ease.)  The basic moral of these studies is that the endocannabinoid system is tightly interwoven with the stress system.


Read the full article on Gizmodo here.


For those too lazy to read the whole thing, here is the tl;dr version as I understand it.

-Marijuana contains more than just THC. It also has cannabidiol.
-Higher ratio of THC to cannabidiol = more preferred "mind high," but also more impaired memory.
-Lower ratio of THC to cannabidiol = more of a knock-you-out, relaxing "body high," and less/no impaired memory.
-Also, (of course), your high will be different depending on the state of your mind, where you are, etc.


Thanks to Gordon for this comment:

Sativa: mind-expanding, creative, giggly, appetite
Indica: Relaxed, pain-relieving, body stone