Aerobic exercise in the treatment of PTSD: An examination of preclinical and clinical laboratory findings, potential mechanisms, clinical implications, and future directions

Exercise and Fear and Safety Learning

Fear conditioning paradigms have been studied for over 100 years and are of great interest to the behavioral and clinical sciences given that several safety learning processes (e.g., extinction learning and recall) are thought to be fundamental to the success of exposure-based therapies for anxiety and related disorders. This chapter provides an overview of preclinical and clinical investigations that examined the effects of exercise on initial fear acquisition, fear extinction learning and consolidation, and return of fear outcomes. This chapter highlights the collective body of evidence suggesting that exercise administered after extinction learning enhances the consolidation and subsequent recall of extinction memories to a greater extent than exercise administered prior to extinction learning. This suggests that the addition of exercise after exposure therapy sessions may improve treatment outcomes for people with anxiety and related disorders. Potential mechanisms are discussed in addition to suggestions for future research to improve our understanding of the effects of exercise on fear conditioning and extinction outcomes.

Pharmacological manipulations of the dorsomedial and dorsolateral striatum during fear extinction reveal opposing roles in fear renewal

Systemic manipulations that enhance dopamine (DA) transmission around the time of fear extinction can strengthen fear extinction and reduce conditioned fear relapse. Prior studies investigating the brain regions where DA augments fear extinction focus on targets of mesolimbic and mesocortical DA systems originating in the ventral tegmental area, given the role of these DA neurons in prediction error. The dorsal striatum (DS), a primary target of the nigrostriatal DA system originating in the substantia nigra (SN), is implicated in behaviors beyond its canonical role in movement, such as reward and punishment, goal-directed action, and stimulus-response associations, but whether DS DA contributes to fear extinction is unknown. We have observed that chemogenetic stimulation of SN DA neurons during fear extinction prevents the return of fear in contexts different from the extinction context, a form of relapse called renewal. This effect of SN DA stimulation is mimicked by a DA D1 receptor (D1R) agonist injected into the DS, thus implicating DS DA in fear extinction. Different DS subregions subserve unique functions of the DS, but it is unclear where in the DS D1R agonist acts during fear extinction to reduce renewal. Furthermore, although fear extinction increases neural activity in DS subregions, whether neural activity in DS subregions is causally involved in fear extinction is unknown. To explore the role of DS subregions in fear extinction, adult, male Long-Evans rats received microinjections of either the D1R agonist SKF38393 or a cocktail consisting of GABAA/GABAB receptor agonists muscimol/baclofen selectively into either dorsomedial (DMS) or dorsolateral (DLS) DS subregions immediately prior to fear extinction, and extinction retention and renewal were subsequently assessed drug-free. While increasing D1R signaling in the DMS during fear extinction did not impact fear extinction retention or renewal, DMS inactivation reduced later renewal. In contrast, DLS inactivation had no effect on fear extinction retention or renewal but increasing D1R signaling in the DLS during extinction reduced fear renewal. These data suggest that DMS and DLS activity during fear extinction can have opposing effects on later fear renewal, with the DMS promoting renewal and the DLS opposing renewal. Mechanisms through which the DS could influence the contextual gating of fear extinction are discussed.

Do the American guideline-based leisure time physical activity levels for civilians benefit the mental health of military personnel?

Backgrounds

This study aimed to clarify the association of American guideline-based leisure time physical activity (PA) level with mental health in 4,080 military personnel in Taiwan.

Methods

The moderate intensity PA level was assessed according to the total running time per week (wk) reported in a self-administered questionnaire over the previous 6  months and was categorized into PA level <150, 150-299, and ≥300  min/wk. Mental stress was assessed by the Brief Symptom Rating Scale (BSRS)-5 for which ≥15 points were classified as great mental stress. Suicide ideation (SI) was graded as 1 for mild, 2 for moderate, and 3 or 4 for severe. Multivariable logistic regression analysis was employed to determine the association between PA and mental health while adjusting for demographics, smoking, alcohol intake, betel nut chewing, and obesity.

Results

As compared to participants with a PA level of <150  min/wk., those with PA levels 150-299  min/wk. and ≥  300  min/wk. had a lower possibility of SI ≥1 [odds ratios (ORs) and 95% confidence intervals (CIs): 0.58 (0.40-0.83) and 0.23 (0.14-0.36), respectively] and SI ≥1 and/or BSRS-5 ≥  15 [ORs: 0.55 (0.39-0.79) and 0.21 (0.13-0.34), respectively]. The possibilities were more significantly lower for SI ≥2 [ORs: 0.37 (0.20-0.68) and 0.10 (0.04-0.26), respectively] and SI ≥2 and/or BSRS-5 ≥  15 [ORs: 0.35 (0.20-0.62) and 0.10 (0.04-0.25), respectively].

Conclusion

Our findings indicate that participating in moderate-intensity leisure time PA level for ≥150  min/wk. may have a positive effect on mental health among military personnel. The impact appears to be even more significant when engaging in a higher PA level of ≥300  min/wk.

The influence of aerobic exercise on model-based decision making in women with posttraumatic stress disorder

Individuals with PTSD often exhibit deficits in executive functioning. An unexplored aspect of neurocognitive functions associated with PTSD is the type of learning system engaged in during decision-making. A model-free (MF) system is habitual in nature and involves trial-and-error learning that is often updated based on the most recent experience (e.g., repeat action if rewarded). A model-based (MB) system is goal-directed in nature and involves the development of an abstract representation of the environment to facilitate decisions (e.g., choose sequence of actions according to current contextual state and predicted outcomes). The existing neurocognitive literature on PTSD suggests the hypothesis of greater reliance on MF vs MB learning strategies when navigating their environment. While MF systems may be more cognitively efficient, they do not afford flexibility when making prospective predictions about likely outcomes of different decision-tree branches. Emerging research suggests that an acute bout of aerobic exercise improves certain aspects of neurocognition, and thereby could promote the utilization of MB over MF systems during decision making, although prior research has not yet tested this hypothesis. Accordingly, the current study administered a lab-based two-stage Markov decision-making task capable of discriminating MF vs MB decision making, in order to determine if moderate-intensity aerobic exercise (either shortly after or 30-minutes after the exercise bout has ended) promotes greater engagement in MB behavioral strategies compared to light-intensity aerobic exercise in adult women with and without PTSD (N=61). Results revealed that control women generally displayed higher levels of MB behavior that was further increased following immediate exercise, particularly moderate-intensity exercise. By contrast, the PTSD group generally displayed lower levels of MB behavior, and exhibited greater MB behavior when completing the task following moderate-intensity aerobic exercise compared to light-intensity aerobic exercise regardless of whether there was a short or long delay between exercise and the task. Additionally, women with PTSD demonstrated less impairment in MB decision-making compared to controls following moderate-intensity aerobic exercise. These results suggest that an acute bout of moderate-intensity aerobic exercise boosts MB behavior in women with PTSD, and suggests that aerobic exercise may play an important role in enhancing cognitive outcomes for PTSD.

Adding physical activity to intensive trauma-focused treatment for post-traumatic stress disorder: results of a randomized controlled trial

Introduction

This randomized controlled trial examined the effectiveness of physical activity added to an intensive trauma-focused treatment (TFT) for post-traumatic stress disorder (PTSD) in comparison to adding non-physical control activities.

Methods

A total of 119 patients with PTSD were randomly assigned to a physical activity condition (PA; n = 59) or a non-physical activity control condition (nPA; n = 60). The 8-day intensive TFT programme consisted of daily prolonged exposure, EMDR therapy, and psychoeducation, which was complemented with physical activities versus controlled mixtures of guided (creative) tasks. As a primary outcome, the change in clinician and self-reported PTSD symptoms from pre-to post-treatment and at 6 months follow-up were measured.

Results

Intent-to-treat linear mixed-effects models showed no significant differences between the PA and nPA conditions on change in PTSD severity. Clinician and self-reported PTSD symptoms significantly decreased for both conditions, with large effect sizes (e.g., CAPS-5 dpre-post = 2.28). At post-treatment, 80.0% in the PA, and 82.7% in the nPA condition no longer met the diagnostic criteria for PTSD. Regarding the loss of Complex PTSD diagnoses this was 92.5% and 95.0%, respectively.

Conclusion

Either with additional physical or non-physical activities, intensive TFT is very effective for the treatment of (Complex) PTSD, as reflected by large effect sizes and loss of diagnostic status in both groups.

Clinical trial registration

Trialregister.nl Identifier: Trial NL9120.

Aerobic exercise after extinction learning reduces return of fear and enhances memory of items encoded during extinction learning

Fear conditioning paradigms are widely used in laboratory settings to discover treatments that enhance memory consolidation and various fear processes (extinction learning, limit return of fear) that are relevant targets of exposure-based therapies. However, traditional lab-based paradigms often use the exact same conditioned stimuli for acquisition and extinction (typically differentiated with a context manipulation), whereas the opposite is true in clinical settings, as exposure therapy rarely (if ever) uses precisely the exact same stimuli from an individual's learning history. Accordingly, this study utilized a novel three-day category-based fear conditioning protocol (that uses categories of non-repeating objects [animals and tools] as conditioned stimuli during fear conditioning and extinction) to determine if aerobic exercise enhances the consolidation of extinction learning (reduces return of fear) and memory (for items encoded during extinction) during subsequent tests of extinction recall. Participants (n=40) completed a fear acquisition (day 1), fear extinction (day 2), and extinction recall (day 3) protocol. On day 1, participants completed a fear acquisition task in which they were trained to associate a category of conditioned stimuli (CS+) with the occurrence of an unconditioned stimulus (US). On day 2, participants were administered a fear extinction procedure during which CS+ and CS- categorical stimuli were presented in absence of the occurrence of the US. After completing the task, participants were randomly assigned to either receive moderate-intensity aerobic exercise (EX) or a light-intensity control (CON) condition. On day 3, participants completed fear recall tests (during which day 1, day 2, and novel CS+ and CS- stimuli were presented). Fear responding was assessed via threat expectancy ratings and skin conductance responses (SCR). During the fear recall tests, the EX group reported significantly lower threat expectancy ratings to the CS+ and CS- and exhibited greater memory of CS+ and CS- stimuli that were previously presented during day 2. There were no significant group differences for SCR. These results suggests that administration of moderate-intensity aerobic exercise following extinction learning contributes to reduced threat expectancies during tests of fear recall and enhanced memory of items encoded during extinction.