Limited evidence to support medical marijuana for treatment of chronic pain, PTSD

Limited scientific evidence exists to support the safety and efficacy of cannabis and cannabinoid products for patients with either chronic pain or PTSD, according to data from two reviews published in Annals of Internal Medicine.

“Physicians will increasingly need to engage in evidence-based discussions with their patients about the potential benefits and harms of cannabis use,” Shannon M. Nugent, PhD, from VA Portland Health Care System and Oregon Health & Science University, and colleagues wrote. “However, little comprehensive and critically appraised information exists about the benefits and harms of using cannabis to treat chronic pain.”

Investigators reviewed several evidence-based medicine databases from inception to March 2017 to assess controlled clinical trials and cohort studies that included data on pain, quality of life or adverse events for adults using plant-based cannabis preparations. They examined study characteristics and quality, and graded the overall strength of evidence for each outcome as high, moderate, low or insufficient.

This systematic review discovered limited evidence on the potential benefits and harms of cannabis use in patients with chronic pain. In total, low-strength evidence from 27 chronic pain trials showed cannabis can lessen neuropathic pain, but was insufficient in other pain populations. Analysis of 11 systematic reviews and 32 primary studies revealed some harms of cannabis use, including increased risk for motor vehicle accidents, psychotic symptoms and short-term cognitive impairment. Cannabis use has potentially serious mental health and poor cognitive effects; however, the data are lacking to determine the amount of risk or who is at greatest risk of harm. Researchers observed no adverse pulmonary effects in younger populations, but did not see sufficient evidence on most other long-term physical harms in heavy or long-term cannabis users, or in older populations.

“Virtually no conclusive information exists about the benefits of cannabis in chronic pain populations, and limited information is available on harms, so methodologically strong research in almost any area is likely to add to the strength of evidence,” Nugent and colleagues wrote. “Of note, many of the studies we found were done in European countries, suggesting that there may be fewer barriers to conducting cannabis-related research there than in the United States, where barriers are substantial.”

Like chronic pain, cannabis use has become increasingly common for patients with PTSD, with more than one-third of patients who seek cannabis for medical reasons reporting PTSD as the motivation for their request in states where medicinal use is legal, according to another systematic review published in Annals of Internal Medicine.

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“Many states list post-traumatic stress disorder as an indication for cannabis use,” Maya E. O’Neil, PhD, from VA Portland Health Care System and Oregon Health & Science University, and colleagues wrote. “However, little comprehensive and critically appraised information is available about the benefits and harms of cannabis use for treating PTSD.”

Researchers analyzed other data from the same medical dispensaries to identify and review current evidence on plant-based cannabis preparations for treating PTSD in adults. They included systematic reviews and observational studies with a control group that reported PTSD symptoms and adverse effects of plant-based marijuana use in adults. Study quality was also graded for overall strength of evidence as high, moderate, low or insufficient.

The evidence examining the benefits and harms of cannabis use in patients with PTSD was insufficient. Analysis of data from two systematic reviews and three observational studies showed insufficient evidence supporting the benefits and harms of cannabis use for treating PTSD. Data from the observational reports revealed that cannabis did not reduce PTSD symptoms compared with nonuse. The investigators found high risk of bias and insufficient overall evidence for the studies. Some of the studies that examined the outcomes of cannabis use in these patients were ongoing and will be finalized within 3 years.

“Virtually no conclusive information exists regarding the benefits of cannabis use in patients with PTSD and information on harms is limited, so methodologically strong research in almost any area likely would add to the strength of evidence,” O’Neil and colleagues wrote. “Comparative effectiveness research of cannabis versus evidence-based pharmacologic and psychotherapy interventions for treating PTSD symptoms is warranted. Research is needed on the potential for mental health and cognitive harms of cannabis use in populations with PTSD, because other mental health disorders and impaired cognitive functioning are common in patients with PTSD.”

In a related editorial, Sachin Patel, MD, PhD, from Vanderbilt Psychiatric Hospital, wrote that the results of these two reviews support the similar findings from another comprehensive review that assessed the health effects of cannabis. Although this suggests there is an increasing consensus in this area of research, physicians are still lacking a firm conclusion about the efficacy of cannabis and cannabinoid products.

“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,” Patel wrote. “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.” – by Savannah Demko

References:

Nugent SM, et al. Ann Intern Med. 2017;doi:10.732/M17-0155.

O’Neil ME, et al. Ann Intern Med. 2017;doi:10.7326/M17-0477.

Patel S. Ann Intern Med. 2017;doi:10.7326/M17-1713.

Disclosures: Nugent and colleagues report no relevant financial disclosures. O’Neil reports no relevant disclosures. Please see the full study for a complete list of all other authors’ relevant financial disclosures. Patel reports grants from Lundbeck A/S.