CBD ‘blocks psychiatric side-effects of THC’

Researchers at a Canadian university have unveiled the molecular mechanisms at work that cause CBD to block the psychiatric side-effects caused by THC.

It has been previously shown that strains of cannabis with high levels of THC and low levels of CBD can cause increased psychiatric effects including paranoia, anxiety, and addictive behaviours, but why that was happening was not fully understood.

Now a research team at Western University in Ontario have investigated the role of a molecule in the brain’s hippocampus called extracellular-signal regulated kinase (ERK), which triggers the neuropsychiatric effects of THC.

Steven Laviolette, a professor at Western’s Schulich School of Medicine and Dentistry, said: “For years we have known that strains of cannabis high in THC and low in CBD were more likely to cause psychiatric side-effects.

“Our findings identify for the first time the molecular mechanisms by which CBD may actually block these THC-related side-effects.”

High levels of THC and low levels of CBD can cause increased psychiatric effects

The research, published in The Journal of Neuroscience, demonstrates that rats that were given THC had higher levels of activated ERK, showed more anxiety behaviours, and were more sensitive to fear-based learning.

Rats that were given both CBD and THC acted like the control rats: they had normal levels of activated ERK, less anxiety behaviours, and were less sensitive to fear-based learning.

Based on these results, the research team proposes that CBD blocks the ability of THC to overstimulate the ERK pathway in the hippocampus and thus prevent its negative side-effects.

“Our findings have important implications for prescribing cannabis and long-term cannabis use. For example, for individuals more prone to cannabis-related side-effects, it is critical to limit use to strains with high CBD and low THC content,” said Laviolette.

“More importantly, this discovery opens up a new molecular frontier for developing more effective and safer THC formulations.”

PhD candidate and Vanier Scholar Roger Hudson, who was lead author on the study, says another interesting finding was that CBD alone had no effect on the ERK pathway.

He added: “However, by co-administrating CBD and THC, we completely reversed the direction of the change on a molecular level.

“CBD was also able to reverse the anxiety-like behaviour and addictive-like behaviour caused by the THC.”

The research team will examine ways to formulate THC with fewer side-effects and to improve the efficacy of CBD-derived therapies.