Does Marijuana impair cognition?

A recent study in the Nature Group journal Neuropsychopharmacology investigates the acute effects of smoking marijuana on cognition. I've always assumed that smoking makes you dumb while you're high, and certainly had never seen any study on the acute effects. Yet it seems those assumptions might be misguided. The double-blinded study looked at a group of 8 females and 10 males who regularly use the drug (average of 24 joints a week!), which were given a ride to the lab then given cigarettes with various concentration of THC, underwent a battery of tests and were finally fed. Great care was taken in preparing the joints:

"During each session, participants smoked a single one-gram marijuana cigarette (0, 1.8, 3.9% Delta9-THC w/w, provided by the National Institute on Drug Abuse). Participants took three standardized puffs from the marijuana cigarette: each puff consisted of a 5-sec preparation interval, followed by 5-sec of inhalation, 10-sec of breath-hold, and 40-sec of exhalation and rest. Cigarettes were tightly rolled at both ends and were smoked through a hollow plastic cigarette holder so that the contents were not visible."

The authors first remark that other than memory recall very little has been investigated about the acute effects of THC, and the only other metric investigated, reaction time in psychomotor tasks, seems unaffected.
The tests they tried was a reaction time test, using both auditory and visual cues on a computer where the test subjects had to press a key. Memory test involved recalling details about stories and sequences of digits. There were also visuo-spatial tasks, mental calculations and various other standardised tasks. The results were somewhat surprising:

" In summary, while subjective ratings and heart rate were significantly elevated in a Delta9-THC concentration-related fashion, cognitive performance was minimally affected following acute marijuana smoking. Participants experienced greater difficulties inhibiting inappropriate responding following the high Delta9-THC concentration cigarette and they required more time to complete several cognitive tests, but their test accuracy rates were unaffected. The finding that accuracy was unaffected by smoked marijuana indicates that heavy, daily, marijuana smokers will not fulfill the DSM-IV criterion for marijuana intoxication that requires impairment of complex cognitive functioning. The consistent slowing of cognitive performance may have significant behavioral effects under some circumstances requiring complex operations that must be accomplished in a limited time frame, such as certain workplace tasks and the operation of machinery and automobiles."

So I guess it doesn't make you dumber, but it does slow you down...

TH-sea

When I was in Japan recently I had the chance to try sea urchin sushi, which were delicious if you don't mind the texture. I hadn't eaten sea urchin since being a kid, when we used to collect them from the local beach in Spain and eat them fresh out of the sea with a dash of lemon. Now I was amused to find out in this article that sea urchin ovaries (the part you eat), has non trivial amounts of anandamide. Anandamide, which is derived from the word bliss in Sanskrit, is the endogenous canabinoid our body secretes. This may explain why some biologists waste their time with invertebrate zoology. More interestingly, the company described in the articles is trying to develop a THC - anadamide hybrid mollecule that would be even more potent against pain.

When thinking about it a little more it didn't surprise me that reproductive organs would contain the ligand, since they are known to express the receptors:

"With respect to reproductive organs, cannabinoid receptors and/or endocannabinoids have been detected in the pituitary gland, testis, Leydig cells, epididymis, prostate, sperm cells, ovary, uterus, oviduct, preimplantation embryo, placenta, embryo, fetus and neonates"

It is thought that in sperm, the anandamide prevents the acrosome reaction, therefore preventing the sperm from activating before it reaches the female tract and also preventing polyspermy during fertilization. The question is, how much anadamide (AEA) is there in reproductive biological fluids?




"We detected AEA, OEA, and PEA in human seminal plasma, mid-cycle oviductal fluid, and follicular fluid analyzed by HPLC/MS"

And the sequela, how much of that stuff do you need to feel a buzz?

"Oral administration of AEA and 2-AG to mice can produce psychotropic effects, suggesting that these endocannabinoids reach the brain ( Di Marzo et al., 1998)."

A quick survey of the literature suggest that 5.8mg/kg is the ED50 of AEA to impair working memory performance (i.e. get a mouse high). So a rough approximation of the dose of milk for an infant to feel the effects is 20,209 L of milk, or for a woman to get high of seminal fluid she would need to chug a good 62,142 L. Notice that calculating the converse would be morally reprehensible.

I suppose the fact that it's so dilute is a good thing for the baby since: "Newborn humans, that had been exposed to marijuana prenatally, exhibit increased tremors, exaggerated responses to stimulation, and spend less time sleeping quietly ( Fried and Smith, 2001).".... but it fails to explain why babies have such munchies...

Harmful marijuana

Today at lunch we were discussing the ironic front page story of a recent "Metro" newspaper cover. In it patients complained about the 1500% markup (150$ an ounce) health Canada is supposedly making on the sell of medical marijuana. It seems health Canada probably wants to sell the therapeutic herb at market value so that patients are not tempted to resell at a profit. In any case, compared to other types of medication it is still cheap, and Canada is being pretty progressive in this matter compared to its southern neighbour. We were also discussing the possible adverse effects of marijuana, considering the recent re-classification that was done in the UK, which while putting marijuana as safer than nutmeg, cigarettes and alcohol, still scored more harmful than ecstasy or LSD. Most of the adverse effect come from the smoke inhalation, which could be avoided by using other delivery methods without combustion. However, propaganda still rages in the States and some of the adverse effects attributed to smoking marijuana (picture above) are definitely not based on sound science, with statements such as: clogged synapses, brain damage, cancer and "destroy" number of chromosomes!!!