Medical benefits of cannabis separated from its side effects

Scientists have found a way to separate medical benefits of cannabis from its unwanted side effects, a breakthrough that may pave the way for safe cannabis-based therapies that do not cause changes in mood, perception or memory.
Scientists at the University of East Anglia, UK, in collaboration with the University Pompeu Fabra in Barcelona had last year discovered how the main psychoactive ingredient in cannabis, known as THC, reduces tumour growth in cancer patients.
Their latest findings, published in the journal PLOS Biology, show how the cognitive effects of THC are triggered by a pathway which is separate from some of its other effects.

That pathway involves both a cannabinoid receptor and a serotonin receptor. When it is blocked, THC can still exert several beneficial effects - including pain relief - while avoiding impairment of memory.
The research was carried out in mice, but it is hoped that the breakthrough will pave the way for safe cannabis-based therapies that do not cause alterations in mood, perception or memory.
"THC, the major active component of marijuana, has broad medical use - including for pain relief, nausea and anxiety," said Dr Peter McCormick, from UEA's school of Pharmacy.

"Our previous research has also found that it could reduce tumour size in cancer patients. However it is also known to induce numerous undesirable side effects such as memory impairment, anxiety and dependence," he said.

"There has been a great deal of medical interest in understanding the molecular mechanisms at work in THC, so that the beneficial effects can be harnessed without the side-effects.
"THC acts through a family of cell receptors called cannabinoid receptors. Our previous research revealed which of these receptors are responsible for the anti-tumour effects of THC.
"This new research demonstrates how some of the drug's beneficial effects can be separated from its unwanted side effects," said McCormick.
The research team carried out behavioural studies in mice and investigated how pathways in their brains operate under THC.
They found that the absence of a particular serotonin receptor (5HT2AR) reduced some of the effects of THC - such as its amnesic effect, based on a standard memory test. But treatment to reduce 5HT2AR did not change other effects of THC, including pain relief.

"This research is important because it identifies a way to reduce some of what, in medical treatment, are usually thought of as THC's unwanted side effects, while maintaining several important benefits including pain reduction," said McCormick.