Cannabinoid modulation of corticolimbic activation during extinction learning and fear renewal in adults with posttraumatic stress disorder

The efficacy of elevating anandamide via inhibition of fatty acid amide hydrolase (FAAH) combined with internet-delivered cognitive behavioral therapy in the treatment of post-traumatic stress disorder: a randomized, placebo-controlled clinical trial

Post-traumatic stress disorder (PTSD) is a severe mental health disorder with limited treatment options. Gold standard treatment includes cognitive behavioral therapies (CBT) that incorporate exposure to traumatic memories to facilitate extinction. CBT can be effective in PTSD, but effects are incomplete and symptoms are prone to spontaneous return. Pharmacologically facilitating fear extinction could potentiate the effects of exposure-based therapy. Here, we explored whether targeting the endocannabinoid (eCB) system, a neuromodulatory system critically involved in fear extinction, would promote the efficacy of exposure-based CBT. Specifically, we tested the effects of elevating the eCB ligand anandamide (AEA) via inhibition of its main degradative enzyme, fatty acid amide hydrolase (FAAH). In this double-blind, placebo-controlled study, patients with PTSD (N = 100; 85 women) were randomized to the FAAH inhibitor (FAAHi) JNJ-42165279 (25 mg b.i.d.) or placebo for 12 weeks. In weeks 5-12, all participants completed an internet-delivered CBT that included exposure-based modules. The primary outcome was clinician-assessed PTSD symptom severity (CAPS-5). Secondary outcomes included self-reported symptoms of PTSD, depression, anxiety, and sleep quality. Blood samples were taken to measure levels of drug and eCBs. Overall, PTSD symptoms improved over time. While FAAHi increased AEA levels, there was no effect of FAAHi on PTSD symptoms or any secondary measure. FAAHi combined with internet-delivered CBT did not improve PTSD symptoms to a greater extent than internet-delivered CBT alone. Thus, FAAH inhibition does not appear to be a suitable adjunct treatment for enhancing CBT in PTSD. This study was registered as Eudra-CT 2020-001965-36.

Medicinal cannabis in the management of anxiety disorders: A systematic review

BACKGROUND

With rising anxiety disorder diagnoses, many individuals are seeking alternatives to standard pharmacotherapies, like medicinal cannabis. This systematic review focuses exclusively on anxiety-related disorders and examines a wide range of cannabis-based preparations and interventions.

METHOD

We searched MEDLINE, EMBASE, CINAHL, and PsycInfo (October-December 2023) for peer-reviewed empirical studies, excluding case series, case studies, and review papers. Inclusion criteria were studies on adults (18+ years) diagnosed with anxiety-related disorders, examining the efficacy or effectiveness of medicinal cannabis. Studies on recreational cannabis or cannabis-use-disorder were excluded. The MASTER and QualSyst tools were used to assess bias.

RESULTS

Fifty-seven studies met the inclusion criteria: 40 % cohort (n = 23), 30 % randomised controlled trials (n = 17), 18 % cross-sectional (n = 10), 12 % qualitative or other designs (n = 7). The MASTER scale revealed a high risk of bias, with a mean score of 62.9 (out of 100) due to inadequate reporting. Among the 13 highest-quality studies, 70 % (n = 9) reported a positive improvement for disorders including generalised anxiety disorder (GAD), social anxiety disorder (SAD), and post-traumatic stress disorder (PTSD). 30 % (n = 4) reported a negative result for conditions like obsessive-compulsive disorder, trichotillomania, test anxiety and SAD. Over 90 % of all studies, including lower quality studies, reported positive outcomes for CBD and THC-based cannabis. However, 53 % (n = 30) either omitted, or included self-reported data on either form and/or dosage.

CONCLUSION

Medicinal cannabis demonstrates potential in reducing anxiety symptoms, but the long-term benefits and overall impact on quality of life remain unclear. Further high-quality, longitudinal research with standardised dosing is needed.

Stress-induced changes in the molecular processes underlying fear memories: implications for PTSD and relevant animal models

Most of the fear literature on humans and animals tests healthy individuals. However, fear memories can differ between healthy individuals and those previously exposed to traumatic stress, such as a car accident, sexual abuse, military combat and personal assault. Traumatic stress can lead to post-traumatic stress disorder (PTSD) which presents alterations in fear memories, such as an impairment of fear extinction and extinction recall. PTSD-like animal models are exposed to a single highly stressful experience in the laboratory, such as stress immobilization or single-prolonged stress. Some days later, animals exposed to a PTSD-like model can be tested in fear procedures that help uncover molecular mechanisms of fear memories. In this review, there are discussed the molecular mechanisms in stress-induced fear memories of patients with PTSD and PTSD-like animal models. The focus is on the effects of estradiol and cortisol/corticosterone hormones and of different genes, such as FKBP prolyl isomerase 5 gene (FKBP5) - FK506 binding protein 51 (FKBP51), pituitary adenylate cyclase-activating peptide (PACAP) - pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1R), endocannabinoid (eCB) system and the tropomyosin receptor kinase B (TrkB) - brain-derived neurotrophic factor (BDNF). The conclusion is that greater emphasis should be placed on investigating the molecular mechanisms of fear memories in PTSD, through direct testing of patients with PTSD or the use of relevant PTSD-like models.

Impaired mnemonic pattern separation associated with PTSD symptoms paradoxically improves with regular cannabis use

Posttraumatic stress disorder (PTSD) is associated with poor hippocampal function and disrupted pattern recognition. Cannabis use is highly prevalent in individuals with PTSD, yet the impact on these cognitive functions is poorly understood. Participants (n = 111) with a range of PTSD symptoms with and without regular cannabis use completed the mnemonic similarity task. We hypothesized that regular use would be associated with alterations in pattern separation ability in individuals with PTSD symptoms. High PTSD symptoms were associated with reduced pattern separation performance in minimal users. Regular users with high PTSD symptoms showed greater pattern separation, but reduced pattern separation with low PTSD symptoms. These results suggest that regular cannabis use may disrupt pattern separation and similar hippocampal-dependent processes, while it may improve pattern separation in individuals with high PTSD symptoms. These cross-sectional results require longitudinal follow-up studies to evaluate the causal effects of regular cannabis use on cognitive function in PTSD.

Dose-dependent effect of acute THC on extinction memory recall and fear renewal: a randomized, double-blind, placebo-controlled study

RATIONALE

Prior work from our lab and others demonstrates that the endocannabinoid system is a promising avenue for improving fear memory deficits in posttraumatic stress disorder (PTSD). Specifically, 7.5 mg of delta-9-tetrahydrocannabinol (THC) decreases fear responding in healthy adults and increases prefrontal cortex activation during extinction learning and fear renewal in adults with PTSD.

OBJECTIVES

The present study will determine whether there is a dose-dependent effect of THC on short-term (24 h) and long-term (one week) fear learning and memory in adults with PTSD.

METHODS

Using a randomized, double-blind, placebo-controlled design, N = 36 adults with PTSD completed the study and were randomized to receive placebo (PBO, n = 11), 5 mg of THC (n = 11), or 10 mg of THC (n = 14) prior to fear extinction learning. Participants completed a Pavlovian conditioning paradigm with extinction recall and fear renewal occurring 24 h and one week later, where we measured concurrent functional imaging and behavioral responses.

RESULTS

Twenty-four hours after drug administration, individuals with PTSD given 5 mg of THC exhibited greater anterior cingulate cortex and prefrontal cortex activation during early fear renewal. One week later, individuals given 10 mg of THC exhibited greater hippocampus activation during extinction recall and prefrontal cortex activation during fear renewal.

CONCLUSIONS

These data suggest that dosing and timing are critical for facilitating fear memory processes in PTSD, and that low-dose oral THC prior to extinction learning can affect brain indices of fear learning and memory both acutely and one week after administration.

Predator odor stress reactivity, alcohol drinking and the endocannabinoid system

Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are highly comorbid and individual differences in response to stress suggest resilient and susceptible populations. Using animal models to target neurobiological mechanisms associated with individual variability in stress coping responses and the relationship with subsequent increases in alcohol consumption has important implications for the field of traumatic stress and alcohol disorders. The current review discusses the unique advantages of utilizing predator odor stressor exposure models, specifically using 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) on better understanding PTSD pathophysiology and neurobiological mechanisms associated with stress reactivity and subsequent increases in alcohol drinking. Furthermore, there has been increasing interest regarding the role of the endocannabinoid system in modulating behavioral responses to stress with an emphasis on stress coping and individual differences in stress-susceptibility. Therefore, the current review focuses on the topic of endocannabinoid modulation of stress reactive behaviors during and after exposure to a predator odor stressor, with implications on modulating distinctly different behavioral coping strategies.

Functional brain changes after alternative pharmacological interventions in posttraumatic stress disorder: A systematic review of clinical trials

BACKGROUND

Posttraumatic stress disorder (PTSD) is a complex and heterogeneous mental health condition that can develop after exposure to a traumatic event. Clinical trials have used alternative pharmacological agents to treat PTSD, but their associated neural correlates remain unclear. The present systematic review aims to summarize the changes in brain function associated with the use of these alternative pharmacological agents in PTSD.

METHODS

Clinical trials using functional magnetic resonance imaging, either at rest or during the performance of tasks, were included if they compared the effects of alternative pharmacological agents between PTSD patients and either trauma-exposed controls or never-exposed healthy controls.

RESULTS

Sixteen studies were included, of which 11 used intranasal oxytocin, 2 used hydrocortisone, and 3 used delta-9-tetrahydrocannabinol (THC). Oxytocin administration was associated with the normalization of functional connectivity between the ventromedial prefrontal cortex and amygdala as well as enhanced the function of brain regions specifically involved in emotion processing (e.g., amygdala), working memory (e.g., dorsolateral prefrontal cortex), and reward (e.g., putamen). Hydrocortisone did not influence brain function at rest or during the performance of an autobiographical memory task, whereas THC was associated with the reduction of the amygdala and increased medial prefrontal cortex activation.

CONCLUSIONS

This systematic review identified preliminary evidence for normalizing brain function after the use of alternative pharmacological agents. Importantly, sex-specific differences were noted, in particular when using oxytocin, that will require further investigation.

Challenges and considerations for treating PTSD with medicinal cannabis: the Australian clinician's perspective

INTRODUCTION

Preclinical and experimental research have provided promising evidence that medicinal cannabis may be efficacious in the treatment of posttraumatic stress disorder (PTSD). However, implementation of medicinal cannabis into routine clinical therapies may not be straightforward.

AREAS COVERED

In this review, we describe some of the clinical, practical, and safety challenges that must be addressed for cannabis-based treatment of PTSD to be feasible in a real-world setting. These issues are especially prevalent if medicinal cannabis is to be combined with trauma-focused psychotherapy.

EXPERT OPINION

Future consideration of the clinical and practical considerations of cannabis use in PTSD therapy will be essential to both the efficacy and safety of the treatment protocols that are being developed. These issues include dose timing and titration, potential for addiction, product formulation, windows of intervention, and route of administration. In particular, exposure therapy for PTSD involves recall of intense emotions, and the interaction between cannabis use and reliving of trauma memories must be explored in terms of patient safety and impact on therapeutic outcomes.