Humans have been using cannabis to relieve pain for about 5,000 years but robust, federally-approved research on marijuana's therapeutic value is just starting to emerge. At the 2015 AAAS Annual Meeting, researchers who have been studying the plants' diverse chemical compounds reported some promising initial results.
The discovery of more than 100 cannabis compounds called cannabinoids over the past several years – along with the identification of an innate cannabinoid system in the human brain and the generation of many synthetic cannabinoids in the laboratory – has led to unprecedented insights, they said.
Animal models and a limited number of human trials have shown that, in addition to THC – the cannabinoid known primarily for its psychoactive effects – compounds such as THCV, cannabigerol, and cannabidiol have medicinal effects on a wide range of afflictions, including chronic pain, nicotine addiction, and spasticity. However, it will take much more research to determine the right combinations of compounds to treat particular problems, as well as the appropriate dosages and drug delivery methods, according to the researchers.
"It's become clear that many of the other cannabinoids have potential therapeutic activity, but it's still too early to tell whether that's going to translate into clinical trial data or not," said Mark Ware from McGill University Health Centre in Montreal, Canada. "This web of intriguing compounds is what's making it so exciting and so interesting, but also so challenging." "It's clear that the weight of evidence now is such that cannabinoids are analgesic drugs," Ware added. "They're not powerful analgesic drugs; their effects are modest. But they're additional tools in the analgesic toolbox that we use when we're treating patients."
Roger Pertwee from the University of Aberdeen in the UK, who has studied cannabinoids since 1968, highlighted the brain's own cannabinoid system, which modulates pain, mood, memory, appetite, and more, as an important test site for research. "There are chemicals in our bodies that act like cannabis, and they target the same sites as THC," he said. "It begs the question of why on Earth we have these receptors in our bodies."
Attempting to answer that question, he and other researchers have begun to uncover a network of cannabis receptors and cannabinoids with complex and sometimes counter-intuitive interactions. Some of them relieve pain or nausea without inducing any kind of "high." Others seem capable of relieving the symptoms of profound psychiatric disorders. Although previous studies have associated cannabis use with schizophrenia, the latest data suggests that some cannabinoids actually have anti-schizophrenic effects.
The well-known short-term effects of THC, which include cognitive and motor impairments, don't seem to impart any long-term damage to adult brains, said Igor Grant from the University of California, San Diego. But he suggests that the compound likely has negative effects on young, developing brains – AND that there is an increased risk of motor vehicle crashes with marijuana, particularly when it's used in combination with alcohol.
More clinical trials with larger numbers of participants are needed to tease out the most effective cannabis-based therapies. But the researchers believe that such studies are on the horizon, especially given the recent and rapid push for marijuana legalisation in the US and elsewhere. Still, government restrictions and the current lack of regulation will continue to hamper cannabis studies for a while at least, they said.
[link url="http://www.aaas.org/news/cannabis-new-frontier-therapeutics"]AAAS release[/link]
[link url="https://aaas.confex.com/aaas/2015/webprogram/Session9659.html"]AAAS abstract[/link]
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[link url="https://aaas.confex.com/aaas/2015/webprogram/Paper14450.html"]AAAS abstract[/link]
[link url="https://aaas.confex.com/aaas/2015/webprogram/Paper14443.html"]AAAS abstract[/link]