Key ingredient staves off marijuana memory loss
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By Arran Frood
Smoking cannabis has long been associated with poor short-term memory, but a study now suggests that the strain of cannabis makes all the difference. In a test of short-term memory skills, only users of "skunk"-type strains exhibited impaired recall when intoxicated, whereas people who smoked hashish or herbal cannabis blends performed equally well whether they were stoned or sober.
The findings suggest that an ingredient more plentiful in some types of marijuana than in others may help to reduce the memory loss that some users suffer.
The key difference between the types of cannabis is the ratio of two chemicals found in all strains. Tetrahydrocannabinol (THC) is the primary active ingredient, and is responsible for the effects associated with the classic "high," including euphoria and giddiness but also anxiety and paranoia. The second chemical, cannabidiol, has more calming effects, and brain-imaging studies have shown that it can block the psychosis-inducing effects of THC2. Skunk-type strains of cannabis contain a higher ratio of THC to cannabidiol than do hashish or herbal types.
Valerie Curran, a psychopharmacologist from University College London who led the latest study, says that if habitual users must partake they should be encouraged to use strains with higher levels of cannabidiol, rather than using skunk. She also argues that studying cannabidiol could provide insight into the mechanics of memory formation, and that it may have therapeutic benefits for disorders involving memory deficits. The findings are published October 1 in the British Journal of Psychiatry.
Cannabis use has increased in recent years--almost as many 16-24-year-olds in the United Kingdom have tried as haven't, according to the 2008 report Statistics on Drug Misuse by the National Health Service--and concerns have been raised that increased levels of THC in 'skunk' varieties owing to agressive plant breeding over the past decade are responsible for a rise in the number of young users displaying mild-to-severe cognitive impairment. However, links to a possible higher incidence and earlier onset of psychotic conditions such as schizophrenia remain controversial, as do associations with long-term psychological problems. Researchers suspect any effects of the drug on mental health could be a result of an increased ratio of THC to cannabidiol in cannabis, because levels of cannabidiol have not kept pace with rising THC concentrations.
Total recall
To test this hypothesis, Curran and her colleagues traveled to the homes of 134 volunteers, where the subjects got high on their own supply before completing a battery of psychological tests designed to measure anxiety, memory recall and other factors such as verbal fluency when both sober and stoned. The researchers then took a portion of the stash back to their laboratory to test how much THC and cannabidiol it contained.
The subjects were divided into groups of high (samples containing more than 0.75 percent cannabidiol) and low (less than 0.14 percent) 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 results suggest that cannabidiol can mitigate THC's interference with memory formation. This is the first study in human to show such effects. One previous study, led by Aaron Ilan, a cognitive neuroscientist at the San Francisco Brain Research Institute in California, failed to find variations in cognitive effects with varying concentrations of cannabidiol.
Ilan attributes the positive finding of Curran and her team to their more powerful methodology in analyzing subjects' own smoking preferences. In the United States, government policy dictates that only marijuana provided by the National Institute on Drug Abuse can be used for research--and it "is notorious for being low in THC and of poor quality," says Ilan.
Lester Grinspoon, professor emeritus of psychiatry at Harvard Medical School in Boston, Mass., who has studied the effects of marijuana on patients since 1967, says that Curran's study is important. "Cannabis with high cannabidiol levels will make a more appealing option for anti-pain, anti-anxiety and anti-spasm treatments, because they can be delivered without causing disconcerting euphoria," he says.
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10 Comments
Add CommentConcerning the anxiety and paranoia aspect, an interesting experiment would be to find out how much anxiety and paranoia is present in a culture where marijuana is legal, compared to a culture in which it is not.
Reply | Report Abuse | Link to thisI suspect there will be little or no negative effects in a culture that condones marijuana use, but quite high effects in cultures that smoking can land you in prison.
Our government's policies on drugs are sheer lunacy.
Reply | Report Abuse | Link to thisThe knee jerk reaction against legalization is unsupportable in the long term.
Exactly my thought - it's not paranoia if they really are out to get you, but the effects are nearly identical.
Reply | Report Abuse | Link to thisI can't recall ever having been disconcerted by euphoria, but this might be the result of too-low levels of cannabidiol.
Reply | Report Abuse | Link to thisGlad to see more studies on the differential effects of cannabidiol (CBD) vs THC. There have been some other studies along these lines concerning CBD as a potential antipsychotic treatment, some epidemiological, some on using CBD in initial clinical trials for people with acute psychotic symptoms, i.e. low numbers only, compared to placebo or to another available antipsychotic medication. All of these have shown promise, with the predictable exception of CBD not being more effective than other currently used antipsychotics for treatment resistent schizophrenia or for bipolar manic phases. These initial clinical trials have been done in Brazil and in Germany. Check out "cannabidiol, antipsychotic" via Google. Much more research needs to be done with this as a potentially useful medication, especially as it seems to have almost no side effects and may have additional benefits vs anxiety and as a neuroprotective agent. Laws do need to change to allow easier research on CBD to further see its relative efficacy at different dosing amounts. Other, legal-economic considerations would have to be worked out as well, e.g. drug companies only research and market something they can make a profit off of because they developed and own the drug. What about naturally occuring substances like this one? Allowing CBD to be marketed as a natural product is not advisable as it is easily converted to THC in labs. A potential solution is to market it as a Canadian company has done for a spray containing a certain THC/CBD balance for nausea caused by chemotherapy.
Reply | Report Abuse | Link to thisOn a clinical anecdotal note, I work with people with psychotic disorders, most of whom have bad reactions to the pot available in N America, but one reported less effects with Jamaican varieties, i.e. less THC, more CBD. This is not to encourage pot use per se, but to validate the fact that some people with psychotic disorders will use pot for the short term calming benefits without recognizing the longer term pro-psychotic and poorer social functioning longer term effects (see a recent article by Jim van Os and co.). The role of pot (both THC and CBD) in psychosis means also that it's more than just a dopamine problem, which has been recognized for quite some time.
My thought to, Culture and society is the ones with the problems, its them that is causing the anxiety and paranoid conditions...becareful of the cops...people been misinformation since the 1940s about about how evil mary jane is, and this has caused a domino effect with succeeding generations...because they have been brought up and brainwashed thinking Weed is bad...and so it plagues on there mind and so they feel some type of guilt of sort thus inducing and causing anxiety and paranoid reactions.
Reply | Report Abuse | Link to thisActually, the CB1r is the most prevalent G-protein coupled receptor in the brain, not just located in the hippocampus. CB2 is also prevalent in the brain, not just in the body. However CB2 is heavily involved with the immune system. There are also currently arguments about whether or not there are CB3 & CB4 receptors
Reply | Report Abuse | Link to thisI wonder if higher levels of cannabidiol can be neatly associated with bush grown varieties and lower levels in hydroponic ones?
Reply | Report Abuse | Link to thisIts good to see that this is being covered properly. In a recent article on another scientific site, there was no mention on the interaction between cannabinoids within the cannabis genus. You will now see many <a rel="dofollow" title="Cannabis Seed" href="http://original-ssc.com/">cannabis seed</a> companies detailing the levels of multiple cannabinoids within each strain and this understanding in hugely important. The presence of both CBD and CBN drastically alter the effects on the user and are essential when looking at beneficial strains for medical use.
Reply | Report Abuse | Link to thisIf the molecular difference between CBD and THC could be ascertained I surmise that an analog drug could be designed, synthesized and tested for its potential against Alzheimer's Disease. Because of the difficulty with in vivo assays I also suggest that in vitro tests could measure some of the biochemical changes known to occur in situ, cellular glucose and calcium transport among them.
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