Marijuana as a treatment for PTSD: What does Scientific Research tell us?

Krista Nelson • Feb 01, 2019

Drs. Jane Walsh and Theresa Fitzgerald will be speaking at the Saint John Public Library on February 28th at 6pm. The title of their talk is: Marijuana as a treatment for PTSD: What does Scientific Research tell us?

MJ & General Health

  • While the popularity of MJ has surged, research on it has lagged well behind, especially re: mental health outcomes
  • Until recently, legal status has been problematic to research in North America
  • Health Canada does not endorse use of medical cannabis
  • College of Family Physicians of Canada indicate that it should only be considered when standard treatments have failed
  • An expert from Harvard Medical School (Staci Gruber) stated:
  • Given that so many people are using MJ, it's my job to help patients and consumers figure out the very best ways in which they might be able to use these products safely and effectively.
  • In 2017, the National Academies of Science, Engineering, and Medicine produced an extensive review on the health effects of cannabis (Ziva Cooper and colleagues)
  • Reviewed studies from 1999 on, found only 3 therapeutic uses were backed buy substantial or conclusive evidence:
  1. Chronic neuropathic pain
  2. Nausea induced by chemotherapy
  3. Spasticity associated with MS
  • Cooper stated:

- Despite that we hear in the media and despite popular belief, there actually is very little known about the therapeutic effects in the human population

  • They noted that chronic pain is the most common reason people cite for medical marijuana
  • The review indicated strong evidence for MJ as a treatment for chronic neuropathic pain over placebo
  • Research also suggest MJ might be able to help reduce or even replace opioids for pain relief
  • Research is ongoing in this area


  • When one of the experts in this field (Bonn-Miller from University of Pennsylvania) first started research in this area in the early 1990s, he could only find 2 published studies on cannabis and PTSD, and he stated:

- It seemed like such a huge gap that needed to be addressed (Zaske, 2018, p.23)

  • By the mid 1990s, scientific studies began to focus on the use of MJ by individuals with PTSD
  • MJ was felt to be particularly helpful in the alleviation of nightmares
  • Interest in MJ grew because many patients with PTSD wanted medication, and there weren't many that work well

Limitation of Early Research

  • Early studies were observational and retrospective (i.e., poor quality)
  • Weren't using gold standard methodology (RCTs)
  • Didn't define or track the type of cannabis used (may differ in potency and constituents)

Recent Research

  • Shishko et al. (2018) conducted a review of medication for PTSD and found:

- Current medication treatments are limited primarily to antidepressants

- Such medicines have produced low remission rates (i.e., 1 in 10 patients have a positive response)

  • They noted that there is a good theoretical rationale for using MJ to treat PTSD due to impact of MJ on brain functioning, may provide different mechanism of action from conventional meds
  • Studies using synthetic form of MJ (Nabilone) have also had promising results (e.g., Jetley et al., 2015)
  • Jetley et al. (2015) did a clinical trial of Nabilone on 47 patients with PTSD who had treatment-resistant nightmares
  • Found adjunctive use of Nabilone resulted in 72% of participants experiencing significant improvements in nightmare intensity, sleep time, quality of sleep, and daytime flashbacks
  • Unfortunately, Shisko et al. (2018) had difficulty finding good quality studies for their review
  • Studies they did find yielded conflicting results (i.e., 3 suggested positive, 2 negative)
  • They noted that Bonn-Miller's research program is the first of it's kind to employ gold standard scientific methodology

Cutting-Edge Research

  • Bonn-Miller is leading 2 of the largest and longest studies ever done on MJ & PTSD
  • The 1st is a double-blind controlled trial that compares different types of cannabis

- 76 participants, mostly military veterans (treatment resistant)

- Assigned to 4 groups: cannabis with high THC, cannabis with high CBD, a strain with equal levels or a placebo

  • Note - the types of cannabis people actually use are often much stronger and come in more varieties than that used in research studies
  • To address this limitation, Bonn-Miller's 2nd study includes 150 participants using MJ purchased at commercial dispensaries in Denver, CO
  • Bonn-Miller's results have not yet been published, but you can learn more via this link
  • Other exciting work being done by Loflin at a VA centre in San Diego (Zaske, 2018)
  • Double-blind placebo-controlled study on the efficacy of cannabis in conjunction with behavioural therapy (PE)

- Although PE is one of the most effective behavioural therapies, significant percentage don't respond, and some patients find it aversive (difficult to participate/complete)

- Loflin will test the hypothesis that using cannabis can increase the efficiency and efficacy of PE and improve its tolerability

- This involves 136 military veterans (and 1st research project involving cannabis funded by US DVA)

  • Important distinction arising from this research between recreational and medical MJ users

- Recreational users admit that they are using to change their mental states

- Many medical users say they don't want to get high, they just want to feel better re physical and/or mental pain

MJ & Cognition

  • Gruber (Harvard Medical School; Zaske, 2018) heads a project called Marijuana Investigations for Neuroscientific Discovery (MIND)
  • She also published a review article with Sagar (2018)
  • They note that studies with recreational users typically show negative cognitive impacts (particularly memory and executive functions)
  • Cognitive problems more prominent in adults who started using during adolescence (possibly due to vulnerability of developing brain, or link with higher frequency and amount used)
  • Increased frequency and amount used also associated with poor cognitive outcomes
  • No clear definition of 'heavy' versus 'light' use makes research complicated
  • Unclear whether findings from recreational users (typically THC) apply to medical users (CBD)
  • Few studies on impact of medical use on cognition
  • Preliminary findings encouraging
  • Example - Gruber et al. (2016, 2018)
  • showed improved cognitive performance, reduced anxiety, reduced use of conventional medications (opioids, benzos, and antidepressants)
  • Gruber concluded:

- This is a difficult landscape to navigate, and while the potential of cannabis for a multitude of indications, symptoms, and conditions is extraordinary, we are in desperate need of empirically sound data (Zaske, 2018, p. 24)

Potential Risks

  • Recent media article suggests more than 7000 veterans in Canada use medical marijuana - and many more use recreationally
  • Danger of legalization - many people with PTSD now purchasing MJ for recreational (i.e., non-prescribed) use

- Need to be aware of risks including drug-drug interactions and masking symptoms that could be better treated with other modalities

  • A review by a group of Pharmacists (Shisko et al., 2018) warned about addiction(i.e., developing Cannabis Use Disorder; CUD)
  • They also expressed concern that due to lack of legalization, distribution has been poorly regulated, large variability in composition (strain, potency, method of use)...hard to predict side effects
  • Potential "numbing/avoidance" effects (like benzodiazepines)
  •  Risk of psychotic disorders in those with certain genotypes, or schizophrenia
  • Long-term effects of MJ unknown


  • No question that we have made progress re treatments for PTSD (medication & behavioural), but lots more work to be done
  • Scientific research on MJ as PTSD treatment has been of poor quality until recently
  • Encouraging research re MJ and chronic neuropathic pain, and preliminary studies re PTSD also promising (improvements re nightmares, anxiety, sleep, cognitive)
  • Despite all the hype - there is limited good quality scientific research due to recent legalization (very early days)
  • Only 2 cannabinoids have been studied with any depth (THC & CBD)
  • Important to consult a health professional who can advise of the risks and benefits (i.e., offer a balanced perspective)

Future Study

  • Effectiveness of MJ vs. placebo vs. other drugs
  • Effective doses for various conditions
  • Efficacy of various cannabinoids
  • Safety of long-term usage, including cognitive impacts
  • Adjunctive use with psychotherapy