We've all heard our parents say it*: "Back in my day, dope was much better than it is now. It wasn't nearly as strong as what you kids smoke today." Like much of the advice our parents give us (like always take out your contacts before you go to bed), this one is also true. The THC (tetrahydrocannabinol - the primary psychoactive compound in cannabis) concentration in marijuana has increased by as much as 12% over the last 30 years. This rise in THC levels is related to increases in the subjective 'high' feelings associated with smoking cannabis, like changes in perceptual sensations, contentedness, and increased appetite. However, THC is also linked to many of the negative consequences of cannabis use, including risk for dependence, attentional bias or distraction, impaired memory and cognition, and the potential emergence of psychotic symptoms.
Alternatively, CBD (cannabidiol - one of the other major chemicals in cannabis that works by increasing endogenous cannabinoid levels in the brain) is associated with the anxiolytic or anti-anxiety effects of marijuana. Additionally, it is thought to act as a protective factor against many of the negative effects the drug can have, including the development of abuse, cognitive impairments, and even psychotic symptoms.
Unfortunately, in addition to the high levels of THC seen in today's cannabis, there is also a significant depletion of CBD. 'Skunk', as it is referred to by users and dealers alike, is the strain of this new high-THC, low-CBD cannabis that is flooding the marijuana market. And it is this drug that is thought to be at the root of the increase in cannabis dependence diagnoses seen over the last decade.
Recent changes in policy and public perception of the risks associated with cannabis have also resulted in an increase in use, particularly among adolescents and young adults, with roughly 50% of high school students reporting having used the drug at some point in their lives. However, despite a previous belief that cannabis was not addictive, there has also been a substantial increase in the number of users seeking treatment for dependence, and nearly 11% of current users qualify as addicted. Skunk smokers in particular are more likely to experience cravings for the drug, go through their stash in shorter amounts of time, and have greater attentional bias to cannabis cues.
Professor Val Curran's group from University College London has been leading the charge on research into the effects of cannabis use, comparing recreational and chronic smokers, and studying the varying effects different strains of cannabis have on the brain. Her group is particularly interested in comparing skunk to THC-CBD strains, and they have discovered much of the evidence for the protective effects CBD has against the development of psychosis and dependence. CBD's action upon the endogenous cannabinoid anandamide seems to be behind the reduction in psychotic experiences in regular smokers, and CBD has even been looked at as a potential treatment for schizophrenia, reducing psychotic symptoms as effectively as some of the anti-psychotic drugs currently prescribed. THC-CBD users also show less distraction to marijuana stimuli than skunk smokers, and they report significantly reduced feelings of craving. There were also no differences in the subjective intoxication effects of smoking either skunk or THC-CBD, indicating it does not alter the psychoactive properties of the drug.
So the question is, where has all the CBD gone? Modern day growing methods using indoor marijuana farms have greatly decreased the risk of detection for cannabis producers by circumventing the need to import cannabis internationally. Cannabis greenhouses also guarantee a more reliable crop, as they are not dependent on changes in weather patterns. However, the 24-hour lighting used in these farms results in an inadvertent destruction of the CBD levels in the plant. Thus, these new strains not only have increased potency with higher THC contents, they also have reduced protective factors against the drug's negative effects. In the producers' eyes, these are just additional economic advantages to growing on an indoor farm, as more dependent users who go through the drug more quickly will result in more cannabis being sold.
These changes in potency raise interesting questions regarding the recent legalization of recreational and medicinal marijuana use in some states. Most pressingly, where and how is this cannabis being produced? And what are the differing levels of THC and CBD present in it? Also, would it be possible to better control cannabis production to avoid its addictive or psychotic-inducing effects? And should we start to think about prescribing CBD to patients currently suffering from THC dependence?
While the developments in cannabis policy may potentially reduce the harm caused to individuals from incarceration or criminal records for minor possession, in terms of the potential psychological effects caused by the drug, it appears we'd be better off smoking our parents' pot.
*Apologies to my parents, who have never actually uttered the above phrase.
**Title pun credit to Claire Gillan.