By Pat Anson, Editor

There is not enough evidence to support the effectiveness and safety of cannabis and cannabinoid products in treating chronic pain or post-traumatic stress disorder (PTSD), according to a pair of new studies published in the Annals of Internal Medicine.

Researchers at the U.S. Department of Veterans Affairs reviewed 27 clinical studies on the benefits and harms of cannabis in treating chronic pain, and found most of the studies were small, many had methodological flaws, and the long-term effects of cannabis were unclear because there was little follow-up in most of the studies.

None of the studies directly compared cannabis with opioid pain medication and there was no good-quality data on how cannabis affects opioid use, according to researchers.

“Although cannabis is increasingly available for medical and recreational use, little methodologically rigorous evidence examines its effects in patients with chronic pain. Limited evidence suggests that it may alleviate neuropathic pain, but evidence in other pain populations is insufficient,” wrote lead author Shannon Nugent, PhD, VA Portland Health Care System.

“Even though we did not find strong, consistent evidence of benefit, clinicians will still need to engage in evidence-based discussions with patients managing chronic pain who are using or requesting to use cannabis.”

Medical marijuana is legal in 28 states and the District of Columbia, and many patients are using it for pain relief. Up to 80 percent of people who seek medical cannabis do so for pain management and nearly 40 percent of those on long-term opioid therapy for pain also use cannabis. Veterans Affairs policy currently doesn’t allow for cannabis use in the huge VA healthcare system, even in states where it is legal.

According to a 2014 Inspector General’s study, more than half of the veterans being treated at the VA have chronic pain, as well as other conditions that contribute to it, such as PTSD.

‘Very Scant Evidence’ on Cannabis for PTSD

More than a third of the patients who use cannabis in states where it is legal list PTSD as their primary reason. But, as with chronic pain, VA researchers found “very scant evidence” to support the use of cannabis to treat PTSD.

“Despite the limited research on benefits and harms, many states allow medicinal use of cannabis for PTSD. The popular press has reported many stories about individuals who had improvement in their PTSD symptoms with cannabis use, and cross-sectional studies have been done in which patients with more severe PTSD reported cannabis use as a coping strategy,” wrote lead author Maya O’Neil, PhD, VA Portland Health Care System.

“However, it is impossible to determine from these reports whether cannabis use is a marker for more severe symptoms or is effective at reducing symptoms, or whether the perceived beneficial effects are the result of the cannabis, placebo effects, or the natural course of symptoms.” 

Clinical evidence may be lacking, but supporters of medical marijuana say they’ve seen plenty of anecdotal evidence that cannabis works for both pain and PTSD.

“They claim no benefits are shown but with the number of people we have met with PTSD that have been able to function and improve with the use of cannabis, I would say the ‘proof is in the pudding.’ Seeing their lives improve tremendously says a lot about success,” said Ellen Lenox Smith, a PNN columnist who is co-director of cannabis advocacy for the U.S. Pain Foundation and a caregiver under Rhode Island’s medical marijuana program. 

“We have not met a person yet that has not been enjoying the improved quality of their life using cannabis for PTSD. We fought a long hard battle to have it included as a qualifying condition and it was worth the battle. Patients are finding peace and calm they were not experiencing before using cannabis. Sleep has improved and without a good night rest, anyone's next day is a terrible struggle.”

Like it or not, the “horse is out of the barn” when it comes to cannabis use, according to an editorial also published in the Annals of Internal Medicine.

“Even if future studies reveal a clear lack of substantial benefit of cannabis for pain or PTSD, legislation is unlikely to remove these conditions from the lists of indications for medical cannabis,” wrote Sachin Patel, MD, Vanderbilt Psychiatric Hospital.

“It will be up to front-line practicing physicians to learn about the harms and benefits of cannabis, educate their patients on these topics, and make evidence-based recommendations about using cannabis and related products for various health conditions. In parallel, the research community must pursue high-quality studies and disseminate the results to clinicians and the public.”