Evidence that cannabis use helps pain or PTSD is lacking, say researchers

By Sally Robertson, B.Sc.Aug 15 2017

Scientific evidence reporting on the use of cannabis for the treatment of chronic pain or post-traumatic stress syndrome (PTSD) is too limited to conclude its safety or efficacy, say researchers from the US Department of Veterans Affairs (VA).

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According to the results of two systematic evidence reviews published in Annals of Internal Medicine, there is insufficient high-quality research to prove the benefits or harms of using cannabis to treat either condition.

Current estimates suggest that one in ten US adults engage in cannabis use, which is legal in 28 states and the District of Columbia, despite it being illegal under federal law.

Up to 80% of people seeking the use of medical marijuana, do so for pain relief. However, when theVA researchers reviewed data from 27 trials looking at cannabis use for chronic pain relief, they found only low-strength evidence that cannabis may alleviate nerve pain and there was insufficient evidence to conclude it may help other types of pain.

On the other hand, there was enough evidence to conclude that cannabis use among the general population could increase the risk of harm, with examples including short-term cognitive impairment, psychotic episodes and motor vehicle accidents.

More than one-third of patients seeking medical marijuana report doing so to relieve PTSD symptoms. Again, when the VA team analysed five studies looking at the use of cannabis in the treatment of PTSD, there was insufficient data to determine whether cannabis would help to relieve symptoms in this patient population.

However, one large observational study focused on veterans with PTSD, did show a small but significant worsening of symptoms among patients who started or continued using cannabis, compared with patients who never started using it or quit.

The current studies highlight the real and urgent need for high-quality clinical trials in both of these areas. If cannabis is being considered for medical use, it should certainly be after all well-established treatments have failed.”

Sachin Patel, psychiatry researcher , Vanderbilt University Medical Center in Nashville, Tennessee