‘Inadequate evidence’ medical cannabis relieves common mental health conditions
There is inadequate evidence that cannabinoids relieve depression, anxiety disorders or attention-deficit hyperactivity disorder, scientists have said.
The meta-analysis also looked at the impact of medicinal cannabinoids on Tourette’s syndrome, post-traumatic stress disorder and psychosis.
Research which combined 83 studies involving 3,000 people suggested their use for the six mental health conditions cannot be justified based on the current evidence.
Scientists said this is due to a lack of evidence for their effectiveness, and because of the known risks of cannabinoids.
But the study, published in the Lancet Psychiatry journal, suggests there is very low quality evidence that pharmaceutical tetrahydrocannabinol (THC) may lead to a small improvement in symptoms of anxiety in individuals with other medical conditions.
Lead author Professor Louisa Degenhardt, of the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney, Australia, said: “Our findings have important implications in countries where cannabis and cannabinoids are being made available for medical use.
“There is a notable absence of high-quality evidence to properly assess the effectiveness and safety of medicinal cannabinoids compared with placebo, and until evidence from randomised controlled trials is available, clinical guidelines cannot be drawn up around their use in mental health disorders.”
Medicinal cannabinoids include medicinal cannabis and pharmaceutical cannabinoids, and their synthetic derivatives, THC and cannabidiol (CBD).
They are increasingly being made available for medicinal purposes in countries like the United States, Australia and Canada, including for the treatment of mental health disorders.
However, researchers say there are concerns around the adverse effects of this availability.
This, they say, is due to a large body of evidence indicating that non-medicinal cannabis use can increase the occurrence of depression, anxiety, and psychotic symptoms.
The authors analysed published and unpublished studies between 1980 and 2018.
Of the 83 eligible studies, 40 were randomised controlled trials (RCTs), and the others were open-label trials, where participants knew which treatment they were taking.
Forty-two of the 83 looked at depression (including 23 RCTs), 31 looked at anxiety (17 RCTs), eight looked at Tourette’s syndrome (two RCTs), three were on ADHD (one RCT), 12 were on PTSD (one RCT), and 11 were on psychosis (six RCTs).
In most RCTs examining depression and anxiety, the primary reason for cannabinoid use was for another medical condition such as chronic non-cancer pain or multiple sclerosis.
The cannabinoid was used to treat the mental health disorder in the studies that looked at the other four disorders.
Only a few RCTs looked at the role of pharmaceutical CBD or medicinal cannabis – most looked at THC, with or without CBD.
Researchers found pharmaceutical THC (with or without CBD) improved anxiety symptoms among individuals with other medical conditions.
However, this may have been due to improvements in the primary medical condition.
The authors suggest further research should study the effects of cannabinoids on anxiety and depression.
According to the analysis, pharmaceutical THC – with or without CBD – worsened negative symptoms of psychosis in one study of 24 people, and did not significantly affect any other primary outcomes for the mental health disorders examined.
It also increased the number of people who had adverse events and withdrawals due to adverse events, compared with placebo across all mental health disorders examined.
Scientists say there is a need for high-quality research to understand the effects of different cannabinoids on a range of outcomes for people with mental health disorders.
They highlight that their analysis and conclusions are limited by the small amount of available data, small study sizes, and the differences in findings between small studies.
Ibuprofen, statins and fish oils ‘may curb depression’
Common painkillers, statins and fish oils may help curb depression, especially if taken with antidepressants, experts say.
A new review found that anti-inflammatory agents, including painkillers such as ibuprofen and aspirin, as well as statins and omega-3 fish oils, could curb major symptoms of depression such as low mood.
Experts from the University of Science and Technology in Wuhan, China, reviewed 26 existing studies for their research in the Journal of Neurology, Neurosurgery and Psychiatry.
The anti-inflammatories included in the studies were non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin; omega 3 fatty acids often found in fish oils; cytokine inhibitors; statins; steroids; antibiotics; a drug used to treat sleep disorders (modafinil); and N-acetyl cysteine, which is used to loosen excess phlegm in people with cystic fibrosis and chronic obstructive pulmonary disorder (COPD).
The results suggested that, overall, these medicines and agents were 52% more effective than placebo at reducing overall symptoms of depression and were 79% more effective in eliminating symptoms than placebo.
The most effective drugs were found to be NSAIDs, omega 3 fatty acids, statins and minocyclines, and the effect was greater if these were added to antidepressants.
However, there was no clear link with improved quality of life, although this may have been due to the small number of studies that examined this, the researchers said.
They concluded: “The results of this systematic review suggest that anti-inflammatory agents play an antidepressant role in patients with major depressive disorder and are reasonably safe.”
Prof Ed Bullmore, head of the department of psychiatry at the University of Cambridge, welcomed the study, but said: “This should encourage further consideration of ways in which we could use a range of anti-inflammatory interventions to help people with depression, perhaps especially people who are already taking a conventional antidepressant drug with limited benefit.
“However, as the authors conclude, further trials will be needed to support licensing and medical prescription of these and other anti-inflammatory agents for depression.”
Professor David Curtis, honorary professor at University College London, said he was not convinced by the findings.
He added: “It is quite misleading to describe the use of anti-inflammatory agents as safe.
“The most effective anti-inflammatory agents used were NSAIDs and although problems are rare, every year thousands of people die from the side-effects of these medications, which are usually taken for chronic pain and are especially risky if taken for long periods of time.”
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