The brain shrinkage they DIDN’T mention
Posted by Dave Bath on 2008-06-16
The hype about the tiny Australian study reporting memory problems for chronic cannabis users is interesting for reasons of what was NOT discussed, including parts from the same paper that show how normal law-abiding citizens can benefit from chronic cannabis use by others.
As usual, the most vocal types never bother to read the fine print or check out other literature.
- Commentators only spoke of the decrease in memory structures (the hippocampus) discussed in the paper, NOT the decrease in fear/agression centres (e.g. the amygdala) reported in the SAME paper.. We have computers and mobile phones to solve memory problems, which don’t affect anyone else anyway, while we don’t have pocket-sized gizmos to make us more peaceful, and less of a threat to others. (I’d rather have louts stoned and apathetic in their loungerooms instead of drunk and outside their homes, where they can cause trouble to other people).
- The hype didn’t discuss the conflicting results from the slightly larger US study "Lack of hippocampal volume change in long-term heavy cannabis users" (Am J Addict. 2005 Jan-Feb;14(1):64-72)
- Perhaps "size doesn’t matter – it’s the way that you use it:" "Spatial working memory in heavy cannabis users: a functional magnetic resonance imaging study" said "cannabis users exhibited increased activation of brain regions typically used for spatial working memory tasks (such as prefrontal cortex and anterior cingulate). Users also recruited additional regions not typically used for spatial working memory (such as regions in the basal ganglia)".
It’s also worth noting that similar hippocampal shrinkage is observed with recent onset post-traumatic stress disorder. No hoo-hah for the same effect, even though it probably involves more people, and people who don’t have a choice in the matter!
Notes:
- My left temporal lobe, the lobe that has the hippocampus, has been affected by epilepsy since birth, so declarative memory is shocking, but my associative memory and the ability to develop "long links" between concepts (necessary for creative thinking) has overdeveloped in compensation. Maybe we should re-headline the paper "Chronic cannabis use causes the same brain changes that also help top pathology finals and perform robust data modelling"
- It’s also been noted (and useful for those with vision problems), that heavy cannabis intoxication improves night vision (see here).
But their results backed up claims by the Observer columnist Sue Arnold, who suffers from retinitis pigmentosa and is officially registered blind. She noticed several years ago that drawing on strong Jamaican skunk suddenly and temporarily enabled her to see things clearly. But Ms Arnold has since warned of side-effects that could impede night-time navigation. “Only trouble was,” she said, “I couldn’t stand up.”
So, when you’re headlights are blown, put the stoner in the driving seat, and when the suburb is hit by a blackout, the stoner will be able to find his keys even if he can’t remember where they are – if he can be bothered, that is.
- There is an artificial hippocampus in the works anyway (see article or picture), which is mooted for use in Alzheimers patients.
Balneus 
Francis Xavier Holden said
Cannabis usage has clear benefits for those with Glaucoma and those with cancer who have nausea effects from chemo and it also benefits those who have illnesses where they have trouble stimulating appetite. The later being a case where science supports long held mythology – “munchies”
Dave Bath said
There are many useful applications for cannabinoids, many contraindications, and a wealth of literature (“Bowman and Rand” my pharmacol textbook from the late 1970s had a particularly good chapter on “social” pharmaceuticals, including betel nuts and kava). As to Toxicity, as my Cassaret and Doull (1st ed) the Tox bible indicated, with an LD50 of about 1000, it doesn’t really deserve a place in a toxicology textbook, so they pretty much pulled it from their second edition. Dunno about newer editions tho.
However, apart from the giggle on night vision, I really wanted to point to the selective reporting from the single paper, and the lack of mention in the press that it was not a groundbreaking study without evidence to the contrary.
Seriously tho, if you are after anything halfway reliable about cannabinoids and anandamides (anandamides are to cannabinoids as endorphins are to opiates), just look for anything that cites Mechoulam. He’s been delving into this since before my time (isolation of active ingredient and synthesis in the 60s, discovery of anandamide later) according to my Merck Index, and was still going strong in 2001 at least – D. Panikashvili, C. Simeonidou, S. Ben-Shabat, L. Hanus, A. Breuer, R. Mechoulam and E. Shohami. An endogenous cannabinoid (2-AG) is neuroprotective after brain injury. Nature 413, 527-531.
Just checked… this Mechoulam guy, born 1930, is STILL publishing in 2008, with new articles already cited – including in the Brit J Pharm!
Google Scholar 2008 papers.
So… not getting into the pro and con debate now… I’ll just say hit the literature
Club Troppo » Missing Link Daily said
[…] down his throat, particularly because it was the government mandating the program.Dave Bath looks past the media hype on long-term cannabis use and provides a few facts the media didn’t bother to […]