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Cannabis shows inconsistent benefits for pain, PTSD

 

Key clinical point: Current evidence is insufficient to support cannabis use for chronic pain or posttraumatic stress disorder.

Major finding: One study of cannabis use for neuropathic pain showed an approximately 30% improvement in pain, but researchers found no significant impact on relieving other types of chronic pain or PTSD symptoms.

Data source: The data come from a chronic pain review that included 27 trials, 11 systematic reviews, and 32 primary studies; and a PTSD review that included 2 systematic reviews and 3 primary studies.

Disclosures: The researchers had no financial conflicts to disclose. The study was commissioned by the Veterans Health Administration.

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Doctors must educate themselves and their patients

 

“The systematic reviews highlight an alarming lack of high-quality data from which to draw firm conclusions about the efficacy of cannabis for these conditions, for which cannabis is both sanctioned and commonly used,” wrote Sachin Patel, MD, PhD, in an accompanying editorial (Ann Intern Med. 2017 Aug 14. doi: 10.7326/M17-1713).

“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,” he cautioned. “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. In this context, these reviews are must-reads for all physicians, especially those practicing in states where medical cannabis is legal,” Dr. Patel added.

Dr. Patel is affiliated with Vanderbilt Psychiatric Hospital in Nashville, Tenn. He had no relevant financial conflicts to disclose, but reported receiving grants from Lundbeck.


 

FROM ANNALS OF INTERNAL MEDICINE

 

Chronic pain and posttraumatic stress disorder are among the top reasons given by patients seeking medical marijuana in states where it is legal, but there is little scientific evidence to support its value for treating either condition, based on the results of a pair of systemic evidence reviews conducted by the U.S. Department of Veterans Affairs.

The findings were published online Aug. 14 in the Annals of Internal Medicine.

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Data on the use of cannabis and related products to treat PTSD and chronic pain are too limited to assess effectiveness, the researchers noted.

In the PTSD study, Maya E. O’Neil, PhD, of the VA Portland (Ore.) Health Care System, and colleagues found no significant evidence to support the effectiveness of cannabis for relieving symptoms (Ann Intern Med. 2017 Aug 14. doi: 10.7326/M17-0477). The researchers reviewed data from two systematic reviews and three primary studies.

One of the larger studies (included in one of the systematic reviews) included 47,000 veterans in VA intensive PTSD programs during 1992-2011. In fact, after controlling for demographic factors and other confounding variables, individuals who continued to use cannabis or started using cannabis showed worse PTSD symptoms than did nonusers after 4 months.

“Findings from [randomized, controlled trials] are needed to help determine whether and to what extent cannabis may improve PTSD symptoms, and further studies also are needed to clarify harms in patients with PTSD,” the researchers noted.

In the review of chronic pain literature, Shannon M. Nugent, PhD, also of the VA Portland (Ore.) Health Care System, and her colleagues examined 27 trials, 11 reviews, and 32 primary studies (Ann Intern Med. 2017 Aug 14. doi: 10.7326/M17-0155).

“Across nine studies, intervention patients were more likely to report at least 30% improvement in pain,” the investigators said. But this finding was specific to tetrahydrocannabinol (THC), the researchers said, and evidence of the ability of cannabis to relieve other types of pain, such as cancer pain and multiple sclerosis pain, was insufficient.

In addition, the researchers found a low strength of evidence association between cannabis use and the development of psychotic symptoms, and a moderate strength of evidence association between cannabis use and impaired cognitive function in the general population. “However, our confidence in the findings is limited by inconsistent findings among included studies, inadequate assessment of exposure, and inadequate adjustment for confounding among the studies” they said.

Although no significant differences were noted in rates of adverse events between cannabis users and nonusers, some data suggested users had an increased risk for short-term adverse events that ranged from dizziness to paranoia and suicide attempts.

Other potential harms associated with cannabis use included decreased lung function, increased risk of complications from infectious diseases, cannabis hyperemesis syndrome, and increased risk of violent behavior.

“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,” the researchers wrote.

The researchers had no financial conflicts to disclose. The study was commissioned by the Veterans Health Administration.
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