Effects of Cannabis on PTSD Recovery: Review of the Literature and Clinical Insights

Abstract

Purpose of Review.

Individuals with posttraumatic stress disorder (PTSD) may use cannabis to reduce symptoms yet are also at risk for developing problematic use. This review outlines theories, summarizes recent empirical studies, and discusses clinical implications of cannabis use and PTSD recovery.

Recent Findings.

Although naturalistic studies and open trials find a relationship between cannabinoids and PTSD symptom reduction, methodological limitations preclude definitive conclusions. The only randomized controlled trial to date found cannabis had no greater effect on PTSD symptoms than placebo.

Summary.

Rigorous studies of the long-term impact of cannabis use on PTSD recovery are needed. Clinicians and researchers must weigh the potential therapeutic effect against the costs and risks associated with long-term cannabis use. Clinicians should consider all available PTSD treatment options, along with client level factors such as the function of cannabis use, motivation to change use, and the potential impact of cannabis on treatment engagement when making clinical recommendations.

Introduction

In the US, 89.7% of adults report exposure to at least one DSM-5 defined traumatic event, and a substantial minority (8.3%) will develop lifetime posttraumatic stress disorder (PTSD)(1). Although trauma-focused psychotherapy and medications, such as selective serotonin reuptake inhibitors, show clear effects on reducing or alleviating PTSD(2–4), a substantial minority of patients either drop out or are non-responders to existing evidence-based treatments(5). Thus, there is interest in considering novel therapeutics for the treatment of PTSD.

One novel approach is the use of cannabinoids from the cannabis plant(6–9). Cannabis sativa, the plant from which widely used medicinal and recreational cannabis products are derived, is made up of several cannabinoids. Two compounds in particular, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), are the most abundant, well-recognized, and well-studied. THC, known for its psychoactive properties, and CBD, known for its calming properties, exert opposing effects (anxiogenic vs anxiolytic respectively) and vary in concentration depending on the strain of cannabis. A thorough review of pharmacological underpinnings and neurobiological effects of cannabinoids is outside the scope of this review. However, in brief, exogenous cannabis compounds, including THC and CBD, exert their effects on the endocannabinoid system through cannabinoid type 1 (CB1) and type 2 (CB2) receptors. CB1 receptors are primarily located in brain regions known for their role in regulating cognitions, emotions, memory, and fear (e.g., prefrontal cortex, hippocampus, amygdala), while CB2 receptors are more prevalent in the peripheral nervous system (PNS) and in immune cells, which are also heavily implicated in anxiety and fear responses (10,11). Thus, exogenous cannabinoids may have therapeutic potential for reducing symptoms associated with anxiety and traumatic stressor disorders. However, despite the preclinical evidence for this potential utility(9), there is a lack of robust clinical trials showing the efficacy of cannabinoids for psychological disorders(12), including PTSD(13,14).

Despite this lack of evidence, PTSD still emerges as one of the primary reasons individuals seek legalized medicinal cannabis(15). Indeed, many individuals with PTSD perceive cannabis as a viable treatment option(16,17). This is potentially concerning as large national studies have shown elevated rates of problematic cannabis use and cannabis use disorder (CUD) in individuals with PTSD(18–20). The presence of a PTSD diagnosis predicts a two-fold increase in the likelihood of developing CUD(18). Individuals who use cannabis with PTSD symptoms compared to those without PTSD symptoms report more cannabis-related problems(21), greater withdrawal severity and cravings(22), as well as a greater likelihood of meeting diagnostic criteria for CUD(20,23), suggesting an increased likelihood of problematic use. The co-occurrence of PTSD and cannabis use is also associated with other negative outcomes including higher alcohol use, more suicidal ideation and depression symptoms, and less financial and employment stability than a diagnosis of PTSD without co-occurring cannabis use(24).

Thus, there are documented negative impacts of the PTSD/cannabis use co-occurrence. Yet, there is growing pre-clinical data and acceptance of cannabis as a possible therapeutic intervention for PTSD. In this review, we outline theories of effects of cannabis on PTSD symptoms and recovery, summarize recent findings regarding the relationship between cannabis use and PTSD recovery, and discuss clinical implications and future directions.

Theorized Relationships between Cannabis and PTSD Recovery

PTSD is a disorder characterized by the persistence of maladaptive fear processing following traumatic events. As defined in the DSM-5(25), PTSD includes reexperiencing of trauma related memories (e.g., intrusive memories, nightmares, cued reminders), effortful avoidance of trauma-related thoughts, feelings, and situations, disruptions in cognitions and mood (e.g., negative beliefs about oneself and the world, lack of positive affect, loss of interest), and hyperarousal (e.g., impaired sleep, hypervigilance, excessive startle response). Potential mechanisms of PTSD symptom development and maintenance include consolidation of the fear memory and failure of natural fear extinction after trauma exposure(26,27). Cannabinoids may facilitate PTSD recovery via symptom management (i.e., anxiolytic effects and coping), by altering memory consolidation/reconsolidation, or by enhancing fear extinction learning(28).

Symptom Management.

Recreational or self-medication use of cannabis is often reported to have anxiolytic, or anxiety reducing, effects(29). Relaxation, anxiety reduction, and stress relief are among the most commonly reported expectations of cannabis use(30–33). Individuals with PTSD often report using cannabis to manage symptoms(17); intrusive reexperiencing(34,35), sleep difficulties(36,37), and anxiety or hyperarousal(21,35) are most frequently cited as motivating cannabis use. Furthermore, cannabis use increases with PTSD symptom severity(35,38) and average PTSD symptom severity, but not daily deviations from average symptom severity, is associated with daily cannabis use(39). Thus, from observational and self-report studies, cannabis is often used to ameliorate or decrease anxiety and trauma-related symptoms.

In both animal and human studies, CB1 agonists show anxiolytic effects at low doses and anxiogenic effects at high doses.(40) However, in real world patients the effects of exogenous cannabis on anxiety and stress are influenced by not only dose but also cannabis composition (THC vs CBD) and use patterns. Although epidemiological naturalistic studies suggest that both THC and CBD are reported as anxiolytic, clinical studies show that while CBD is reliably linked to anxiolytic effects in both animal and human studies, THC is associated with anxiogenic, or anxiety increasing, effects, especially in high doses(29). In addition, characteristics of the cannabis user may impact effects. For example, in rodents, chronic stress has been shown to cause anxiety reactions to normally anxiolytic producing doses of a CB1 agonist(41). These findings have potential implications for individuals with stressor-related disorders like PTSD who are using whole plant cannabis, containing both THC and CBD, and tendency to differentially experience anxiolytic vs anxiogenic effects.

Cannabis use is often noted as a way of coping with PTSD symptoms, although other motives such as enhancement of enjoyment and conformity are also reported(22,38). Coping-oriented cannabis use motives are more common in individuals with clinically significant levels of PTSD symptoms compared to those without(22,37), and coping motives help explain the relationship between PTSD, frequency of cannabis use, and CUD(42). Accordingly, coping with anxiety and other negative emotions resulting from the disorder is often posited as an explanation for its potential effectiveness.

Effects on Memory Consolidation.

An alternative way cannabinoids may impact trauma-related disorders is altering processing of the trauma memories themselves. In memory-focused disorders such as PTSD, memory reconsolidation processes may play a role in reactivating and subsequently altering previously consolidated memories(43). This hypothesis argues that, by systematically retrieving a conditioned stimulus (CS), previously stable, consolidated memories can be returned to a temporary labile state that allows for either strengthening or weakening of the original memory(44). During this CS-activated window of time, subsequent pharmacological blockage via protein synthesis inhibitors or behavioral extinction may erase or permanently overwrite previously learned associations during the original fear conditioning(45–47). Cannabidiol, potentially through binding to fatty acid proteins decreasing anandamide metabolism, may similarly alter fear memory reconsolidation and enhance extinction(48).

Several meta-analyses suggest the potential utility of memory reconsolidation, via pharmacological and behavioral methods, albeit with smaller and more variable effects with behavioral procedures and in human clinical applications(49–51). In rodents, CBD disrupts the reconsolidation of contextual fear memory after brief retrieval (52–56), resulting in less fear. This reconsolidation effect is likely dependent on the activation of CB1 receptors located in the prelimbic subregion of the medial prefrontal cortex(57). The role of THC in contextual fear memory reconsolidation effects is not as clear (see (57,58)). Interestingly, given that drug cravings can occur via recall of related environmental cues, in rodents, CBD has been shown to impair reconsolidation of place preference for environments previously paired with morphine and cocaine(59).

Although there is some promise of CBD to disrupt reconsolidation of fear memories and enhance consolidation of extinction learning in non-clinical human samples(60), the application of CBD as a reconsolidation agent in the treatment of disorders such as PTSD have yet to be evaluated in well-powered clinical trials. Finally, the potential disruptive effects of CBD on memory reconsolidation are in contrast with its potential facilitative effects on extinction; and alternatively, as will be reviewed below, CBD may enhance exposure-based psychotherapy by facilitating fear extinction(61).

Effects on Extinction Learning.

There is a robust literature supporting heightened fear responding and deficits in extinction learning (i.e., the attenuation of fear after repeated presentation of the CS in the absence of the US) as both characteristic and integral to PTSD(62–64). CB1 agonists, such as THC, enhance fear expression in contextual fear conditioning tasks(65,66) likely through effects on the amygdala and hippocampus(67), suggesting a cannabinoid role in fear acquisition. Regarding extinction of fear, low doses of CB1 agonists facilitate the extinction of fear in rodents(68). Similarly, administration of CBD results in enhanced contextual fear extinction in rodents(69), although this effect is likely dependent on the strength of the fear conditioning itself, with CBD impairing extinction for weak conditioning and improving extinction for strong conditioning(70). However, repeated administration(71) and high doses(72) of a CB1 agonist result in less extinction compared to administration of control substances.

Data on the effect of CB1 agonists in human extinction learning is emerging, with two experimental studies showing short-term facilitation of extinction learning in healthy participants administered THC(73,74). Administration of CBD in humans has resulted in mixed effects depending on timing of administration; with no effects on extinction of fear memory if administered before extinction, but facilitation effects if administered after extinction(60). Consistent with the rodent literature, individuals who use cannabis chronically show deficits in both differentiation between fear and safety cues during fear conditioning and in fear extinction compared to non-users(75), although this study did not directly administer cannabinoids. To our knowledge, no studies have directly tested the effects of cannabinoids, whether plant based or synthetic, on extinction learning in those with PTSD but pre-clinical studies may suggest a potentially clinically useful role for cannabinoids aiding the therapeutic extinction of fear.

Summary of Theoretical Models.

These different explanations for how cannabinoids might impact PTSD recovery are crucial to differentiate. Inherent in symptom management approaches, where the use of CBD in particular is emphasized as theoretically helpful, is the need to continue using cannabis, indicating that underlying pathology processes would not be expected to change. Memory reconsolidation and extinction theories suggest that CBD and to a lesser extent THC, particularly in regard to fear extinction, may impact and ultimately change the processes leading to PTSD, gains that could be maintained even after discontinuation of cannabis use. Of note, evidence-based exposure and cognitive therapies for PTSD that target memory and extinction processes (4,76), show sustained improvements even after active treatment has ended. If cannabis is acting on these processes, we might expect some degree of sustained effects.

Empirical Review of Recent Research on Effects of Cannabis on PTSD Recovery

Given the limited number of randomized controlled trials on this topic, the following selective review on clinical and treatment studies focus on the next best available levels of evidence such as open trials, prospective, and retrospective studies with a focus on the last five years and earlier studies that directly manipulated cannabis administration. See Table 1 for a description of reviewed studies.

Table 1.

Summary of Clinical and Observational Human Studies on Cannabis and PTSD Recovery

Study	Cannabis Type	Design	Sample Admission Criteria	Sample Size (N)	Primary Outcome Measure(s)	Study Aims and Findings
Administration Studies: Effects of Administered Cannabinoids on PTSD Symptoms
Randomized Controlled Trials
Bonn-Miller et al., 2021	Plant (THC, CBD, THC+CBD)	Double-blind, cross-over	Veterans diagnosed with PTSD of ≥ 6-month duration and moderate severity	80	PTSD symptom severity (CAPS-5)	Aims: Tested safety and efficacy of smoked cannabis for the treatment of PTSD Results: No differences in PTSD symptom reduction between conditions. All groups showed reduction in PTSD symptoms over 4 weeks (THC:d = 1.99; CBD: d = 0.79; THC+CBD:d = 0.83; placebo: d = 1.30).
Open Trials and Chart Review
Cameron et al. 2014	Nabilone	Retrospective Chart Review	Adult male incarcerated individuals with serious mental illness	104	PTSD symptom severity (PCL-C), number of nights with nightmares, average number of hours slept	Aims: Assessed efficacy of prescribed nabilone for off-label indications. Results: Improvement in PTSD symptom severity (d = 1.52), nightmares (d = 2.14), and hours slept (d= 1.69).
Elms et al., 2019	CBD	Open Trial	Community sample diagnosed with PTSD	11	PTSD symptom severity (PCL)	Aims: Examined the clinical benefit of CBD as augmentation to routine psychiatric treatment Results: 8 weeks following baseline, 91% reported a decrease in PTSD symptoms (mean symptom decrease of 28%).
Fraser, 2009	Nabilone	Open Trial	Community sample diagnosed with PTSD and ≥1 weekly nightmare frequency	47	Nightmare frequency	Aims: Examined effects of nabilone on treatment-resistant nightmares. Results: 72% reported decreased severity or cessation of nightmares. 91% experienced a recurrence of nightmares upon nabilone withdrawal.
Jetlyetal. 2015	Nabilone	Double-blind placebo-controlled	Military Personnel diagnosed with PTSD and reporting current distressing nightmares and difficulty with asleep	10	Nightmare intensity and frequency; sleep quality and quantity	Aims: Compared the effects of nabilone to placebo on frequency and intensity of nightmares. Results: Reductions in frequency and intensity of nightmares were greater among those who received nabilone compared to placebo. There were no between-group differences in changes in sleep quality and quantity.
Roitman et al. 2014	Delta-9 THC	Open Trial	Community sample Diagnosed with PTSD	10	PTSD symptom severity (total and symptom clusters), sleep quality, nightmare frequency and impairment	Aims: Examined efficacy of THC for PTSD. Results: Reductions in hyperarousal symptoms, nightmare frequency, nightmare impact and sleep quality.
Effect of Cannabis on PTSD Treatment Response
Bedard-Gilligan et al. 2018	Naturalistic	RCT	Community sample diagnosed with PTSD, excluded for substance dependence	200	Treatment dropout, adherence, PTSD symptom severity	Aims: Examined the effect of cannabis use on treatment engagement and outcome. Results: Individuals reporting recent cannabis use (OR = 3.38) or a lifetime CUD diagnosis (OR = 2.39) were more likely to drop out. Recent cannabis use predicted worse in vivo (β = −.29) and imaginal (β = −.22) exposure adherence. Lifetime CUD predicted worse in vivo (β = −.21) and imaginal (β = −.21) exposure adherence. Those with a lifetime CUD had higher posttreatment PTSD symptoms compared to those without (β = .22).
Hale et al., 2020	Naturalistic	Longitudinal	Veterans diagnosed with PTSD and either a history or no history of cannabis use	114	PTSD symptom severity	Aims: Compared individuals who do and do not use cannabis on the effects of a residential PTSD treatment program. Results: No significant differences between those who reported cannabis use and those who did not on PTSD symptom change pre- to post-treatment.
Ruglass et al., 2017	Naturalistic	RCT	Community sample diagnosed with PTSD and substance use disorder (not cannabis use disorder)	136	PTSD symptom severity	Aims: Examine the effect of cannabis use on in-treatment and end-of-treatment outcomes. Results: Higher weekly cannabis use was associated with greater PTSD symptom severity in early treatment, but with lower weekly PTSD symptom severity at the end of treatment. Baseline cannabis use did not predict end of treatment PTSD symptom severity.
Observational Studies
De Aquino et al. 2020	Naturalistic	Longitudinal	Veterans diagnosed with PTSD and either pre-treatment ≥7 days cannabis use or no pre-treatment cannabis use	1,413	PTSD symptom severity	Aims: Compare individuals with and without pre-treatment cannabis use on change in PTSD symptoms following residential PTSD treatment. Results: Cannabis use did not have a significant effect on reduction of PTSD symptoms.
Bonn-Miller et al. 2020	Naturalistic	Longitudinal	Veteran and community samples diagnosed with PTSD and either use cannabis or do not use cannabis	150	PTSD symptom severity	Aims: Compare individuals who do and do not use cannabis on PTSD symptom change over one year. Results: PTSD symptom severity decreased in both groups over time and individuals who use cannabis had a greater rate of symptom reduction over time compared to individuals who do not use cannabis (R2 = .13).
Lafrance et al., 2020	Naturalistic	Longitudinal	Community sample self-identified with PTSD and who use medical cannabis	404	Intrusions, flashbacks, irritability, anxiety	Aims: Examined changes in PTSD symptoms prior to and shortly after cannabis use. Results: PTSD symptom reduction was reported after cannabis use, with a 62% reduction in intrusion severity, 51% reduction in flashback severity, 67% reduction in irritability severity, and 57% reduction in anxiety severity. PTSD symptom severity ratings did not change significantly over time.
Greeretal.,2014	Naturalistic	Retrospective	Community sample diagnosed with PTSD and a history of cannabis use	80	PTSD symptom severity	Aims: Compared PTSD symptom severity between two periods of time: a time period when cannabis was used and a time period when cannabis was not used. Results: Participants self-reported lower PTSD severity during periods of cannabis use compared to periods of non-use (d= 4.42).

Notes. Effect sizes of results are reported if included in the study. Effect sizes were calculated for studies where it was not included and the sample size was N > 50. Naturalistic refers to participant self-report of cannabis use patterns without study manipulation or control of dosing, type, etc.

Naturalistic Studies.

Utilizing naturalistic methods such as surveys, chart reviews, retrospective assessments, and ecological momentary assessment (EMA) or app-delivered symptom tracking, researchers monitor symptoms over extended periods of time without administering intervention. There is some evidence documenting the immediate benefit of cannabis for PTSD symptom relief including intrusive thoughts, flashbacks, irritability, and anxiety(77). Across studies, there is a positive association among cannabis use, dose, and symptom relief and there appears to be only rarely a negative impact on, or symptom exacerbation of, PTSD symptoms(77).

Studies comparing individuals who use cannabis and those who do not on changes in PTSD symptoms over longer periods of time have been more mixed. Bonn-Miller and colleagues(78) found that individuals who used cannabis at least once per week in the past three months had a decrease in PTSD symptoms and were 2x more likely to not meet DSM-5 criteria for PTSD over a one-year follow-up period compared to those who did not use cannabis. However, another study found no difference in PTSD symptom change over four months for those who use cannabis (seven or more days in the past 30 days) and those who do not use cannabis(79). A retrospective assessment of self-reported PTSD symptom decreases among individuals who use cannabis found a significant decrease in PTSD symptoms measured by the CAPS-5 when comparing a past time period when cannabis was not used with a period when cannabis was used(80). This study should be interpreted with caution because participants were selected for reported cannabis-related PTSD symptom benefits, cannabis quantity and frequency were not assessed, and there were other incentives for participants to report PTSD-related benefits of cannabis use. In many of these studies, measurement issues exist such as the use of individuals who self-identify with PTSD rather than through validated measures or interviews(77), and the use of PTSD measures that have not been psychometrically validated(79). In addition, the varied definitions and assessments of cannabis use make it challenging to generalize findings across studies. Thus, at present, naturalistic cannabis use may have some immediate benefit on PTSD symptoms, but the impact of long-term cannabis use on PTSD is not clear.

Cannabis Administration Studies.

Clinical studies involving drug administration provide some of the strongest evidence as to the therapeutic potential of cannabis for PTSD symptoms. Bonn-Miller and colleagues(82) conducted a double masked randomized control trial (RCT) showing reductions in interviewer-rated PTSD symptoms across high THC (d = −1.99), high CBD (d = −0.79), high THC+CBD (d = −0.83), and placebo conditions (d = −1.30). There was no difference between conditions, including with the placebo, potentially due to the high prior use of cannabis in this sample, expectancy effects, or natural fluctuation of PTSD symptoms over the short, 3-week duration of the trial.

Open trials administering cannabinoids with no comparison group have found a 28% decrease in general PTSD symptoms(83) as well as decreases in hyperarousal symptoms(84) and frequency or intensity of nightmares (50–72% report improvement)(83,85,86). These trials are characterized by small, predominately male, veteran samples and considerable variation in type of cannabinoid administered, dose, and length of administration. Most of the open trial studies administered a synthetic THC-based cannabinoid such as Nabilone(85–87), with the study by Elms and colleagues(83) administering CBD. In addition, across studies the method for determining PTSD diagnosis was inconsistent. While two studies used a well-validated measure of PTSD(84,86), others relied only on self-report measures(85) or assessment measures were not clearly described(88).

Further understanding of the impact of cannabis on PTSD recovery can be gained from studies that examined cannabis use in the context of PTSD treatment. Notably, cannabis use does not appear to be associated with PTSD treatment response among individuals with either a primary PTSD diagnosis(89,90) or co-occurring PTSD and substance use disorder diagnoses(91). However, naturalistic cannabis use may negatively impact treatment in that recent cannabis use is associated with greater treatment dropout and worse adherence to therapy homework(89).

Overall, there is a need for methodologically rigorous studies that determine the effect of cannabis administration on PTSD symptoms. Studies examining the long-term impact of cannabis on PTSD symptoms are needed to examine the efficacy of cannabis, particularly when considering the lack of increased efficacy compared to a placebo(78) and reports from open trials that individuals experience a recurrence of symptoms after cannabinoids are withdrawn(85)., Notably, Bonn-Miller and colleagues(92) found that less reduction in PTSD symptoms during residential treatment was associated with higher cannabis use frequency four months following discharge. These reports are more consistent with a symptom management explanation as opposed to a shared mechanism explanation.

Clinical Implications and Recommendations

A scientific understanding of the effects of cannabinoids on PTSD recovery is emerging. However, legislative and policy recommendations are ahead of the scientific literature, which is still unclear on whether cannabinoids are an effective intervention for PTSD. Historically accepted clinical practice for patients with a diagnosis of PTSD was to reduce and/or eliminate any substance use behaviors before addressing trauma-related symptoms using medication or therapy approaches. However, in recent years, clinical guidance has shifted as evidence has accumulated that PTSD and substance use co-occurrence can be effectively addressed simultaneously(93). Yet, many clinicians find themselves working with patients with PTSD and current cannabis use and are unclear how to proceed. Questions abound: How do we understand the effects cannabis might be having on our patients, both specific to PTSD symptoms and more generally? How do we best manage patient expectations, motivations, and engagement in standard evidence-based treatments for PTSD when cannabis use is present? Over the last several years, our research team has been conducting a clinical trial (NCT02874898) examining implementation and efficacy of an evidence-based trauma-focused treatment, daily imaginal exposure, for patients with PTSD who also use cannabis heavily (5+ days per week) or do not use any cannabis. Several insights around common clinical challenges have emerged.

Assessment of Cannabis Use and Its Function.

When trying to conceptualize the functional effects of cannabis, coping motives are a key factor in why patients with PTSD use cannabis(42). Assessing perceived rewards or benefits of use are crucial for moving toward better personalized medicine. Understanding use patterns (including type of cannabinoid used, THC and CBD concentrations, chronicity, and frequency/quantity), motivations for use, and consequences of use is important to treatment planning and implementation to best address both PTSD, motivation to change cannabis use, and any harms associated with cannabis use. Standardized, psychometrically validated measures such as the Comprehensive Marijuana Motives Questionnaire(94) and Marijuana Consequences Checklist(95) should be considered both for treatment planning and evidence-based assessment purposes throughout treatment. Being aware of use patterns, such as dosing, specific compounds being used, and chronicity, can inform our clinical decision making and can inform on the likely effects of cannabis on maintaining vs worsening vs helping PTSD symptoms.

Motivations to Change Use.

Along with the increased legalization and availability of cannabis has come increasingly positive attitudes toward cannabis, including shifts toward perceptions of cannabis as harmless(96). It is important to recognize that patients who present for PTSD treatment while using cannabis are clearly not achieving full PTSD therapeutic benefit from their cannabis use. And yet, it has been our observation that many patients still perceive their cannabis use as helpful, or even necessary, for their PTSD recovery. Motivations to change cannabis use patterns may be low in patients who ascribe to these beliefs. A clinical observation from our work is that use motives may also change with successful trauma-focused cognitive behavioral therapy, shifting from medicinal to recreational use.

A potential conclusion from existing clinical studies of cannabinoids for treatment of PTSD is that therapeutic effects are not sustained when active use is discontinued(85), consistent with cannabinoids acting as a symptom management technique. This is coupled with withdrawal effects of stopping cannabis use that affect almost one half (47%) of individuals who use cannabis regularly and discontinue use, and include but are not limited to irritability, sleep problems and anxiety(97). Stopping cannabis use is likely to increase distress and discomfort, at least temporarily. However, there are likely costs and risks associated with long-term, chronic cannabis use including the development of CUD(98). Evidence-based strategies for increasing commitment to changing substance use, such as motivational interviewing (MI)(99), can be helpful if it is determined that the patient is experiencing significant harms related to cannabis use. Of note, MI has been shown as effective in reducing alcohol use in individuals with PTSD(100) but has not been empirically tested in those with PTSD who are specifically using cannabis.

Engagement in Treatment.

Individuals using substances often have more difficulty engaging in PTSD treatment, including higher rates of non-adherence and dropout(101). At least one study has documented this effect in patients using cannabis specifically(89), which is not surprising given that cannabis use is related to reduced motivation(102). Thus, clinicians should be vigilant to issues that might affect retention and engagement in this population. This could include additional strategies for engagement (e.g., MI) or treatment adaptations. For example, our study is employing an intensive, daily imaginal exposure protocol that does not require outside of session practice or homework. This type of approach can reduce barriers to engagement and facilitate treatment completion, even in patients that are traditionally harder to retain. It is important to recognize that hypothesized therapeutic effects of cannabis on mechanisms such as memory consolidation and facilitating extinction learning (68,103) will only occur if the patient using cannabis also engages in certain relevant approach behaviors that promote these same processes, either naturalistically or through engagement in treatment. Thus, supporting patient engagement with treatment techniques is likely needed to expect PTSD treatment benefits related to cannabis use.

Conclusions and Future Directions

Of the chemicals in cannabis sativa, THC and CBD are the most well-studied, exerting anxiogenic and anxiolytic effects, respectively. The administration of exogenous cannabinoids is seen as having therapeutic potential for reducing anxiety and traumatic stressor disorders. Individuals with PTSD report using cannabis to manage an array of symptoms, with anxiety or hyperarousal being the most frequently cited symptoms that motivate cannabis use(21,35). Cannabis is theorized to facilitate PTSD recovery through symptom management, disruption of memory reconsolidation, and enhancement of fear extinction learning.

There is initial evidence indicating that cannabis reduces PTSD symptoms as found in, for example, an app-based study of cannabis use and PTSD symptom tracking(77) and open trials administering cannabinoids(83–86). However, the benefit of cannabis on PTSD symptoms likely disappears once use is stopped(85). There is a tremendous need to determine the long-term effect of cannabis use on PTSD recovery, particularly given that use may cause problems for some, including negatively affecting PTSD treatment engagement. The potential risk for withdrawal symptoms from long-term use and the anxiogenic effect of THC point to a need for studies to examine the necessary dose, course, and type of cannabinoid optimal to experiencing symptom benefits while minimizing negative effects. Well-designed large-scale studies with rigorous design elements including randomization, control groups, masked condition assignment, and long-term follow-up are needed.

Clinicians treating individuals with PTSD and cannabis use should consider coping motives and perceived rewards from cannabis use in their case conceptualization. Assessing the potential negative consequences of cannabis use for the client’s life, as well as for treatment engagement, can inform when to implement strategies such as MI to reduce harms related to cannabis use. Given that chronic use of cannabis may be necessary for sustained benefits on PTSD symptoms, it is important to consider whether the costs of long-term cannabis use outweigh the perceived benefit on PTSD symptoms management, when a full course of first-line PTSD treatment options have not been tried. Finally, patient preferences are important to accommodate, as they promote treatment engagement, better outcomes(104), and are cost effective(105). Thus, clinicians and patients are encouraged to thoughtfully consider both the potential benefits and consequences of treating PTSD with cannabinoids as well as strategies to understand and manage patient-initiated cannabis use if it occurs during active treatment. Although the current literature does not support cannabis as an evidence-based treatment for PTSD, it also does not currently support it as a harmful or ineffective approach, leaving clinicians with a gray area to implement personalized treatment recommendations and strategies to promote recovery following trauma.