Table 1.

Study characteristics.

First Author, Country, Setting	N	Age (Range, M (SD))	Gender (M/F)	Military Status	PTSD/GD diagnosis	Design, Context, Intervention, Control/Comparison, Duration	Time Point	ACT Elements	Reported Outcomes
Shirk et al. (2022), US, VA, mental health outpatient care	3	46–57	3/0	100% army, veterans. Persian Gulf and Vietnam era(s)	Not reported	Case series/feasibility study, group setting, manualised treatment, 9 weekly sessions, homework, duration 3 months.	Pre-test, post-test	Adapted MBRP	Reduced gambling behaviour (instances), cravings (impulsivity), emotional dysregulation Instances reduced from 21x – 3x per month across participants. Collectively impulsivity decreased from M = 50.7 to M = 44.3 and emotional dysregulation reduced from M = 56.3 to M = 40.0
Reyes et al. (2022), US, technology based	23	M 31.22 (5.53)	0/23	Veterans, Iraq/Afghanistan era	PTSD – DSM-5/ PCL-5	Quasi experiment, app-based delivery, daily/weekly activity engagement prompts, duration 1 month.	Pre-test, during, post-test	Mindfulness, ACT	Global PTSD scores, experiential avoidance, mindfulness PTSD – T1 to T2 M-11.61 (SD 12.71) and T3 M-27.78 (SD 14.22), p < .001. Experiential avoidance significantly improved at T3 M-7.71 (SD 6.97), p < .001 Mindfulness and PTSD symptoms were negatively significantly corelated (r = −.632)

Ramirez et al. (2021), US, trauma focused outpatient care	311	M 37.6 (8.06)	193/118	Active duty	PTSD – DSM-5/ PCL-5	Quasi experiment, group setting with 2 (60-90 min) one-to-one sessions, homework, duration 6 weeks.	Pre-test, during (weekly)	Exposure therapy combined with ACT	Global PTSD scores; PDS-5 and PCL-5, experiential avoidance. PTSD – PDS-5: M = −20.47 (SD 16.13), p < .000, d = 1.33. PCL-5: M = −18.12 (SD15.49), d = 1.19. 25.4%−28.3% (were below the PTSD clinical cut-off) Avoidance significantly reduced (M = −6.86, SD 9.30, d = 0.88)
Smith et al. (2021), US, technology based	1	Late 20s	1/0	Veteran	PTSD – DSM-5/ PCL-5	Single case study; individual ‘telehealth’ video conferencing setting, manualised treatment, 19 60-minute sessions, duration 5 months.	Pre-test, during, post-test, 1 month follow up	ACT	Global PTSD, experiential avoidance. PTSD reduced by 79%. Avoidance reduced (unreported)
Reyes et al. (2020a), US, VA, technology-based	23	M 31.22 (5.53)	0/23	Veterans, Iraq/Afghanistan era	PTSD – DSM-5/ PCL-5	Feasibility study, app-based delivery, daily/weekly activity engagement prompts, duration 4 weeks.	Pre-test, during and post-test; 4 weeks	Mindfulness, ACT	Global PTSD scores and app usability. PTSD reduced (−12.39, p < .001). App usability score – ‘excellent’ M 85.11 (SD 19.44)
Reyes et al. (2020b), US, technology-based	9	M 31.44 (not reported)	3/6	Veterans	Not reported	Feasibility study, mixed methods, daily/weekly activity app engagement prompts, in-person interviews conducted at the intention conclusion, duration 2 weeks.	Pre-test, during and post-test	Mindfulness, ACT	Global PTSD scores and app satisfaction. PTSD – deceased significantly (F = 5.08, p = .027). App satisfaction scores – ‘good’ (M 72.75) Qualitative themes elicited: instituting a sense of progression; integrating a sense of rhythm; inculcating a sense of contribution
Kelly et al. (2020), US, VA, post-service reintegration programme	1	50s	1/0	Veteran, Gulf era	PTSD – DSM-5/PCL-5 and SCID-5	Single case study, manualised treatment, 12 50-minute sessions, homework, duration 12 weeks.	Pre-test, during, post-test, 3 months follow up	Social support focused ACT (ACT-SS)	Global PTSD scores and negative thoughts PTSD – mean reduced 12.5% Cluster of negative thoughts reduced but unreported
Dindo et al. (2020), US, VA, polytrauma clinical care	42		42/0	Veterans	PTSD – DSM-IV/SCID-I	Pilot and follow-up RCT (ACT versus TAU), development and evaluation study, manualised treatment, homework, group-based, duration 3 months. TAU = psychoeducation	Pre-test, post-test, pilot measured at 2 weeks and 3 months, RCT measured at 3 months	ACT	Global PTSD scores, psychological flexibility PTSD and psychological flexibility saw non-signification reduction
Gobin et al. (2019), US, VA, multi-site clinical study	117	M 35.75 (8.1)	94/23	Veterans, Iraq/Afghanistan era	PTSD – DSM-IV/PCL-M	Secondary data study related to RTC by Lang et al. (2017) (see below). Data scrutinised for gender differences in intervention outcome.	Pre-test, post-test, 6, 9, 12 months follow up	Mindfulness, ACT	Global PTSD scores Gender difference over time (F(2,109.15) = 412, p < .05). Women had significant result (F(1,19.47) = 11.88, p < .01) PTSD – greater effect with ACT versus PCT (d = 1.20)
Wharton et al. (2019), US, VA, PTSD clinical care	21	M 54.5 (all >50)	21/0	Veterans, Vietnam era	PTSD – DSM-IV/ PCL-M	Pilot, quasi experiment, group therapy versus individual therapy, 12 weekly 60-minute sessions (individual therapy) or 90-minute session (group therapy), manualised ACT, duration 12 weeks.	Pre-test, post-test, 3 months follow up	ACT	Global PTSD scores, experiential avoidance, hyperarousal PTSD – group therapy (t(9) = 2.67, p < .05,g = 0.69). Individual therapy (t(7) = 2.42, p < .05, g = 1.24) Avoidance – group therapy (t(8) = 2.92, p < .05, g = 0.851), individual therapy (t(7) = 3.40, p < .05, g = 1.04) Hyperarousal – individual therapy (t(7) = 2.58, p < .05, g = 1.184)
Meyer et al. (2018), US, VA	43	M 45.26 (6.6)	38/5	Veterans	PTSD – DSM-5/PCL-5 and CAPS-5	Pilot, quasi experiment, 12 weekly sessions, manualised treatment, one-to-one setting, homework, duration 3 months.	Pre-test, post-test, 3 months follow up	ACT	Global PTSD, experiential avoidance PTSD – reduced (M −12.76, d = 0.96) at intervention end and at 3-month follow-up (M −12.34, d = 0.88) Experiential avoidance reduced (M −6.8, d = 0.62).
Lang et al. (2017), US, VA, multi-site clinical study	160	M 34 (8)	128/332	Veterans, Iraq/Afghanistan era	PTSD – DSM-IV/PCL-M	RCT of ACT versus PCT (person-centred treatment), manualised treatment, 12 60-minute one-to-one sessions, homework, duration 12 weeks.	Pre-test, post-test, 6, 9, 12 months follow up	ACT	Global PTSD scores. PTSD – reduced overall (d = 0.78) but no between condition differences
Shipherd et al. (2016), US, VA, mandatory post-deployment assessment/re-assessment	1524	M 28.65 (6.72)	1372/152	Activity duty	PTSD – DSM-IV/PCL-C NR	RCT comparing 4 conditions (TAU; PIT (psychoeducation)); ‘PIT + change’ (PIT + CBT); ‘PIT + acceptance’ (PIT + ACT), workshop/group face-to-face setting, 1 single session 50-60 min for ‘change’ or ‘acceptance’ or 20-30 min for PIT, duration 1 session.	Pre-test, post-test, 1 month follow up	Acceptance-based	Global PTSD scores PTSD – ‘reset’ condition outperformed TAU (p = .047, d = 0.09) and PIT (p = .021, d = 0.14). No significant difference between ‘reset’ and ‘control’
Blevins et al. (2011), US, military-base Guardsmen training	144	M 30 (9.70), control M 32.4 (8.70)	134/10	Guardsmen, Iraq/Afghanistan era	PTSD – DSM-IV/PCL	Quasi experiment, control versus ACT, workshop/group setting; 1 single two-hour session, duration 2-hours.	Pre-test, post-test, intervention group 2 months follow up, control group 4 months follow up	Acceptance-based	Global PTSD scores PTSD – reduced over time (M-4.561 (CI −8.05, −1.07), p < .05) but no significant between-group difference

Note: US, United States; VA, Veteran Affairs Administration; M (SD), mean (standard deviation); OR, odds ratio; CI, confidence interval; RCT, randomised control trial; TAU, treatment as usual; ACT, acceptance and commitment therapy; ACT-SS, acceptance and commitment therapy for social support; PIT, psychoeducation; PCT, patient centred treatment; MBRP, mindfulness-based relapse prevention; DSM, Diagnostic and Statistical Manual; PTSD, post traumatic stress disorder; GD, gambling disorder; PCL, Patient Checklist; PCL-M Patient Checklist Military; PCL-C, Patient Checklist Civilian; PDS, post traumatic diagnostic scale; PSSI, post traumatic stress disorder symptom scale; SCID, I/5 – structured clinical interview for Axis I disorders/DSM; CAPS-5, clinically administered PTSD scale for DSM-5.