Group schema therapy for personality disorders: Systematic review, research agenda and treatment implications

Figures & data

Table I. Key words and search terms utilized in the electronic database screening.

Key word	Search terms
Schema therapy	Schema AND therap*
Group	Group OR class OR program
Effectiveness	Effective* OR efficacy* OR “RCT” OR “randomi* control* trial” OR utility OR usefulness
Personality disorder	Personality AND (disorder* OR pathology* OR difficult*)

Table II. Design, population and methodological characteristics of included studies.

	Study Citation; Country	Design	Population (Setting)	Conditions excluded	N; Mean Age (SD); Female %	Condition/s (n)	TAU (frequency)	Mon-ths FU	Attrition	Diagnostic Method (cut-off)	Main Aim
1	Arntz et al. (2022); UK, Australia, Germany, Greece & Netherlands	RCT	BPD (outpatient)	Low IQ; Psychotic disorder; DID; SUD; ADHD; NPD; AnPD	495; 33.6 (9.4); 86.2%	IGST (123) vs PGST (125) vs TAU (246)	“optimal” therapy on site match-ed to ST intensity	12	IGST (26%); PGST (38%); TAU (36%)	BPDSI-IV (>20); SCID-II	Determine the efficacy of GST for BPD, and whether group or combined individual/ group delivery is more effective.
2	Dickhaut and Arntz (2014); Netherlands	Uncontrolled Pilot	BPD (comm-unity)	Psychotic disorder; Mania; ADHD; SUD; AN; ASD; NPD; AnPD	18; 28.5 (8.7); 100%	Therapists untrained in GST (8) vs Therapists trained in GST (10)	N/A	6	33.3% in year 1; 5.6% in year 2	SCID-II, BPDSI-IV (>20)	Assess the efficacy of combined group and individual ST for BPD
3	Doomen (2018); Netherlands	Naturalistic (single group)	Cluster C PDs (community)	Psychotic symptoms; SUD; Low IQ	8; 34.0 (NR); 63%	SFDT (8)	N/A	N/A	0%	Clinical interview w/ DSM-5 criteria	Determine the effectiveness of schema-focussed drama therapy in Cluster C PDs
4	Farrell et al. (2009); US	RCT	BPD (comm-unity)	Psychotic disorder; Low IQ	32; 35.6 (8.69); 100%	SFT + TAU (16) vs TAU (16)	Individual supportive therapy (weekly)	6	SFT + TAU (0%); TAU (25%)	DIPD-R; BSI	Determine the effectiveness of adding Group SFT to individual TAU for BPD.
5	Fassbinder et al. (2016); Germany	Naturalistic (single group)	BPD (comm-unity)	Psychotic disorder; Low IQ; SUD	10; 35.0 (13); 100%	GST (10)	N/A	24	10%	SCID-II; BPDSI-IV	Investigate the feasibility and effectiveness of GST for severe BPD in a German context
6	Hilden et al. (2021); Finland	RCT	BPD (comm-unity)	Psychotic symptoms; Suicide risk; SUD; Dissociation	42; 31.0 (8.80); 92%	SGT + TAU (28) vs TAU (14)	Supportive therapy (varied) + meds.	N/A	SGT + TAU (15%); TAU (14%)	SCID-II	Determine the feasibility and effectiveness of GST alongside TAU for BPD outpatients
7	Koppers et al. (2020); Netherlands	Naturalistic (multi-ple groups)	PDs w/ depressive symptoms (community)	Suicide risk; AnPD; Psycho-social problems	225; 39.4 (NR); 64%	SCBT (225)—post-hoc high/low depression comparison	N/A	3	23%	Clinical interview w/ DSM-IV criteria	Determine the efficacy of SCBT in groups with PDs, with high and low severity depressive symptoms.
8	Koppers et al. (2021); Netherlands	Naturalistic (multiple groups)	PDs (comm-unity)	Suicide risk; AnPD; Psycho-social problems	194; 37.3 (9.25); 42%	GST (194)	N/A	3	28.40%	Clinical interview w/ DSM-IV criteria	Examine the outcomes of GST for PDs on symptom severity, EMS and modes
9	Nenadić et al. (2017); Germany	Naturalistic (single group)	BPD or Cluster C PDs (inpatient, sub-acute)	Psychotic disorder; Cognitive impairment/ TBI	9; 23.9 (NR); 87.5%	GST (9)	N/A	N/A	11%	SCID-II	Determine the effectiveness of short-term GST for BPD or Cluster C PDs
10	Peeters et al. (2021); Netherlands	Naturalistic (single group)	Cluster C PDs w/ chronic anxiety (comm-unity)	NR	62; 34.4 (9.3); 72.6%	SCHerp (62)	N/A	N/A	6%	MINI; SCID-II	Examine the effects of combined GST and ERP for Cluster C PDs with chronic anxiety
11	Reiss et al. (2014); US	Uncontrolled Pilots	BPD (inpatient)	Psychotic disorder; Chronic MDD; Low IQ; AnPD; NPD	92; 31.2 (7.2); 95.7%	P1 (41) vs P2 (36) vs P3 (15)	N/A	P1/P2 (N/A); P3 (3)	P1 (2.4%); P2 (2.7%); P3 (6.2%)	BSI in P1; SCID-II in P2/3	Evaluate the effectiveness of intensive inpatient GST for BPD
12	Skewes et al. (2015); Australia	Mixed Method;Naturalisatic + Focus group	AvPD or BPD w/ depression & anxiety (comm-unity)	Psychotic symptoms; current emotional crisis; SUD	8; 33.8 (7.9); NR	GST (8)	N/A	6	25%	Clinical interview using DSM-IV-TR criteria	Explore the acceptability, feasibility, and effectiveness of GST for mixed PDs
13	Van Dijk et al. (2022); Netherlands	Natur-alistic (multiple groups)	Cluster B and C PDs (outpatient)	Bipolar 1; Psychotic disorder; SUD; Suicide risk; Neurocog. disorder	19; 65.0 (NR); 58%	GST + PMT (19)	N/A	2	5%	SCID-II	Evaluate a GST protocol enriched with psychomotor therapy for older adults
14	Van Vreeswijk et al. (2020); Netherlands	RCT	AvPD or BPD (comm-unity)	Psychotic symptoms; SUD; Suicide risk; Low IQ; ADHD	58; NR (NR); 75.9%	SMBCT + TAU (28) vs COMET + TAU (30)	Psychiatrist consultati-ons (varied) + meds.	1	SMBCT + TAU (35.7%); COMET + TAU (33.3%)	MINI; SCID-II	Investigate the effectiveness of two eight-week group therapies for mixed PDs

Note. Abbreviation: N = population, SD = Standard Deviation, n = sample, TAU = Treatment As Usual, FU = Follow-up, UK = United Kingdom, RCT = Randomized Control Trial, BPD = Borderline Personality Disorder, IQ = Intelligence, DID = Dissociative Identity Disorder; SUD = Substance Use Disorder, ADHD = Attention Deficit Hyperactivity Disorder; NPD = Narcissistic PD, AnPD = Antisocial PD, IGST = Individual and Group ST, PGST = Primarily Group ST, BPDSI-IV = BPD Severity Index (Giesen-Bloo et al., 2010), SCID-II = Structured Interview for the DSM (First & Gibbon, 2004); AN = Anorexia Nervosa, ASD = Autism Spectrum Disorder, GST = Group ST, NR = not reported, SFDT = Schema focussed drama therapy, US = United States, SFT = Schema Focussed Therapy. DIPD-R = diagnostic interview for BPD-Revised (Zanarini et al., 1990), BSI = borderline symptom inventory (Conte et al., 1980), meds. = medication, SGT = schema group therapy, SCBT = schema cognitive behavioural therapy, EMS = early maladaptive schema, SCHerp = Schema/Exposure Response Therapy, PMT = Psychomotor Therapy, MINI = mini-international neuropsychiatric interview (Sheehan et al., 1998), P = pilot, SMBCT = schema mindfulness based cognitive therapy, COMET = competitive memory therapy.

Table III. Intervention characteristics and treatment outcomes of included studies.

	Intervention						Within group outcomes		Between group outcomes
	No. sessions; Duration	Session Length; Frequency	M:T	Treatment focus (Manual)	Additional Treatment; Frequency	% of GST	Pre-Post (d)	Pre-FU (d)	Post (d)	FU (d)
1	122-135; 24 months	90 minutes; weekly–monthly	8–9:2	Mode-based (Farrell & Shaw, 2012)	60-minute individual ST; quarterly (PGST) and weekly (IGST)	92% PGST; 51% IGST	In TAU, BPDSI (1.60); BPD-C (0.95); GAF (0.94); SOFAS (0.85); WASAS (0.87); WhoQoL (.68); BSI (0.88); YSQ (1.02); SMI (0.87–1.11); Happ. (0.69). In PGST, BPDSI (1.80); BPD-C (1.11); GAF (1.11); SOFAS (1.12); WASAS (1.14); WhoQoL (0.71); BSI (1.03); YSQ (1.17); SMI (0.94–1.22); Happ. (0.91). In IGST, BPDSI (2.36); BPD-C (1.24); GAF (1.38); SOFAS (1.21); WASAS (1.10); WhoQoL (0.89); BSI (1.15); YSQ (1.29); SMI (1.11–1.32); Happ. (0.78)	In TAU, BPDSI (2.41); BPD-C (1.42); GAF (1.41); SOFAS (1.27); WASAS (1.09); WhoQoL (.84); BSI (1.16); YSQ (1.23); SMI (1.03–1.35); Happ. (.79). In PGST, BPDSI (2.70); BPD-C (1.66); GAF (1.66); SOFAS (1.68); WASAS (1.61); WhoQoL (0.91); BSI (1.45); YSQ (1.54); SMI (1.18–1.56); Happ. (1.22). In IGST, BPDSI (3.55); BPD-C (1.86); GAF (2.07); SOFAS (1.82); WASAS (1.55); WhoQoL (1.27); BSI (1.69); YSQ (1.77); SMI (1.51–1.76); Happ. (.97)	NR	PGST and IGST combined were superior to TAU in reducing BPDSI (0.73), though IGST was superior to TAU (1.14) and PGST (.84). PGST was not superior to TAU (.30). PGST and IGST combined were superior to TAU in all secondary measures, though IGST was only superior to PGST in the WhoQoL (0.36). PGST was only superior to TAU in the WASAS (0.52) and Happ. (0.42).
2	Unclear, approx. 140; 24 months	90 minutes; weekly	8–10:2	Mode-based (Farrell & Shaw, 2012)	Baseline medication + 60-minute individual ST; weekly	60%	NR	BPDSI (2.72); BPD-C (2.34); SCL-90 (1.49); Happ. (1.77); EuroQol (.94); WhoQol (1.31); SMI (1.16–1.48); YSQ (1.64)	d NR. First cohort had slower reduction in BPD-C, SCL-90 and YSQ; slower increase in Happ., EuroQol, and WhOQol; and less improvement in SMI. BPDSI recovery was higher in second cohort, 18.7% vs 66.5.	BPDSI (no sig. difference); BPD-C (no sig. difference); SCL-90 (no sig. difference); Happ. (NR); EuroQol/ WhOQol (NR); SMI (NR); YSQ (no sig. difference)
3	6; 3 months	150 minutes; fortnightly	8:2	Mode-based (Farrell & Shaw, 2012) w/ drama as experiential	N/A	100%	MOS (.50–.88); SMI (.25–.80)	N/A	N/A	N/A
4	30; 8 months	90 minutes; weekly	6:2	Schema-focus (Young, 1990) w/ psychoed. and DT	Baseline medication + TAU; weekly	60%	For SFT + TAU, BSI (2.48); SCL-90 (.72); DIB-R (4.29); GAF (1.39); 94% remission. For TAU, BSI (.09); SCL-90 (-.25); DIB-R (.49); GAF (.14); 16% remission.	For SFT + TAU, BSI (2.96); SCL-90 (1.17); DIB-R (4.45); GAF (2.67); 94% remission. For TAU, BSI (.04); SCL-90 (-.13); DIB-R (.35); GAF (-.14); 16% remission.	BSI (1.97); SCL-90 (1.39); DIB-R (1.35); GAF (1.39)	BSI (2.81); SCL-90 (2.20); DIB-R (2.42); GAF (3.13)
5	Unclear, approx. 52; 12 months	100 minutes; weekly	10:2	Mode-based (Farrell & Shaw, 2012)	Baseline medication + 60-minute individual ST; weekly	63%	BPDSI (1.18); BPD-C (.61); BSI (.54); GAF (.96); SOFAS (.63); WSAS (.34); WhoQol (.34); EuroQol (.10); Happ. (.02); SMI (.55–.92); YSQ (.67); Days of hospitalization (4.49)	BPDSI (1.81); BPD-C (1.17); BSI (1.55); GAF (1.37); SOFAS (.84); WSAS (1.09); WhoQol (1.90); EuroQol (.71); Happ. (1.70); SMI (1.33–1.51); YSQ (1.34); Days of hospitalization (5.13)	NR	N/A
6	20; 5 months	90 minutes; weekly	5-7:2	Mode-based (shortened version of [2012])	Baseline medication + TAU; varied	CT	For SFT + TAU, BSL-23 (.44); OASIS (.26); AUDIT (1.34); PHQ-9 (.38); SDS (.11–.25). For TAU, BSL-23 (.59); OASIS (.58); AUDIT (.11); PHQ-9 (.39); SDS (.04–.36)	N/A	d NR. No sig. differences between groups across all measures.	N/A
7	20; 5 months	120 minutes; weekly	8-9:2	Schema-focus (Broersen & van Vreeswijk, 2012)	1–2 60-minute individual CBT; weekly + 60-minute individual ST; monthly	53%	Overall, SCL-90 (0.5); YSQ (0.56); 50% achieved reliable reduction in symptoms. In PD-Lo, SCL-90 (0.15–0.49); YSQ (0.44–0.56); UCL (0.06–0.29) In PD-Hi, SCL-90 (0.29–1.25); YSQ (0.40–0.72); UCL (0.06–0.35)	Overall, SCL-90 (0.45); YSQ (0.49); 44.6% achieved reliable reduction in symptoms. In PD-Lo, SCL-90 (0.04–0.43); YSQ (0.39–0.54); UCL (0.08–0.32). In PD-Hi, SCL-90 (0.18–1.28); YSQ (0.36–0.58); UCL (0.01–0.52).	M, SD and d NR. No between group differences across measures or in reliable change in symptoms, PD-Lo (44.9%) vs PD-Hi (57.1%). Higher rates of remission in PD-Lo (32.6%) vs PD-high (17.5%)	M, SD and d NR. Greater reduction in SCL-90, GSI, and depression in the PD-Hi. Higher rate of reliable change in PD-Hi (62%) vs PD-Lo (32.4%). No difference in remission rates, PD-lo (24%) vs PD-Hi (21.1%)
8	40-60; 10–15 months	90 minutes; weekly	6-7:2	Schema and mode-based (Aalders & van Dijk, 2012)	N/A	100%	SCL-90 (0.65); YSQ (0.97); SMI (0.90–1.00); Remission rate 30%	SCL-90 (0.61); YSQ (0.99); SMI (0.91–0.94); Remission rate 28.9%	N/A	N/A
9	12-15; 6–7 weeks	50 minutes; biweekly	9:2	Mode-based (shortened, German version of [2012])	Baseline medication + 1-2 60-minute individual CBT; weekly	53%	SMI (0.44–0.69); YSQ (0.22); BSCL-53-S (0.86)	N/A	N/A	N/A
10	72; 6 months	110 minutes; triweekly	8:2	Mode-based with art/drama techniques (adapted [2012])	60-minute individual ST; fortnightly + 240-minute individual ERP; weekly	55%	OQ-45 (.75); SMI (.62–.66)	N/A	N/A	N/A
11	10-18; 10–18 weeks	480–510 minutes; weekly	8-11:1-2	Mode-based (Farrell & Shaw, 2012)	Baseline medication + 1-1.5 60-minute individual ST; weekly	85%	In P1, BSI (2.15); GAF (2.84). In P2, BSL-21 (1.34); SCL-90 (.98) In P3, BSL-95 (.73); SCL-90 (.96)	In P3, BSL-95 (.50); SCL-90 (.43). No sig. difference in BPD symptoms.	NR	NR
12	20; 5 months	60 minutes; weekly	8:2	Mode-based (adapted van Vreeswijk & Broersen, [2013] w/ experiential emphasis)	60-minute individual ST; monthly	80%	YSQ (2.20); MCMI-II (.76–2.96); SCL-90 (1.06); SMI (1.32–1.69); Remission rate 50%	YSQ (2.70); MCMI-II (.82–3.07); SCL-90 (1.14); SMI (1.22–1.66); Remission rate 63%	N/A	N/A
13	18; 6 months	90–105 minutes; weekly	4–8; 2	Mode-based (adapted van Vreeswijk & Broersen, [2013] for older adults)	PMT; weekly	CT	YSQ (.12); SMI (.54–.75); MANSA (.10)	YSQ (.40); SMI (.68–1.09); MANSA (.36)	NR	NR
14	8; 2 months	90 minutes; weekly	8:2	Mode-based (adapted van Vreeswijk et al. [2014] with mindfulness as cognitive component)	TAU; varied	CT	* GSI (-.05); MAAS (.00); YSQ (.04–.11); SMI (−.04–.12) In SMBCT + TAU, 20% recovered; 16.7% impr-oved; 40.0% no change; 23.3% deteriorated; In COMET + TAU, 17.9% recovered; 14.3% impr-oved; 46.4% no change; 21.4% deteriorated	* GSI (.29); MAAS (.03); YSQ (.01–.29); SMI (.22–.25)	M, SD and d NR. No sig. differences between conditions in GSI, RSES, MAAS, YSQ and SMI.	M, SD and d NR. No sig. differences between conditions in GSI, RSES, MAAS, YSQ and SMI.

Note. If effect sizes were not reported, these were calculated using Means and Standard Deviations as available. Abbreviation: No. = number, M:T = member to therapist ratio, GST = group schema therapy, d = cohen’s d as reported or manually calculated via means and standard deviations, FU = follow up, PGST = Primarily Group ST, IGST = Individual and Group ST, TAU = treatment as usual, BPDSI = borderline personality disorder Severity Index (Giesen-Bloo et al., 2010), BPD-C = BPD Checklist (Bloo et al., 2017), GAF = Global Assessment of Functioning Scale (Hall, 1995), SOFAS = social and occupational functioning assessment scale (Hilsenroth et al., 2000), WASAS = work and social adjustment scale (Mundt et al., 2002), WhoQoL = world health organisation quality of life scale (WHO, 1996), CT = Cannot Tell, BSI = Borderline syndrome index (Conte et al., 1980), YSQ = Young Schema Questionnaire (Young et al., 2003), SMI = Schema Mode Inventory, Happ. = 1-term happiness scale, SCL-90 = symptom check list (Derogatis & Savitz, 2000), EuroQoL = Euro quality of life scale (Group, 1990), NR = not reported, sig. = significance, MOS = mode observation scale (Bernstein et al., 2009), N/A = not applicable, psychoed. = psychoeducation, DT = distress tolerance, SFT = schema focussed therapy, BSI = borderline symptom inventory (Conte et al., 1980), BSL-23 = borderline symptom list (Bohus et al., 2007), OASIS = overall anxiety severity and impairment scale (Norman et al., 2006), AUDIT = alcohol use disorders identification test (Reinert & Allen, 2002), PHQ-9 = patient health questionnaire (Kroenke & Spitzer, 2002), SDS = Sheehan disability scale (Luciano et al., 2010), CBT = cognitive behavioural therapy, PD-Lo = personality disorder with low depression, UCL = Utrecht coping list (Schreurs et al., 1993), PD-Hi = personality disorder with high depression, M = mean, SD = standard deviation, BSCL-53 = brief symptom checklist (Franke, 2016), OQ = Outcome Questionnaire (Lambert et al., 1996), ERP = exposure response prevention, P = pilot study, w/ = with, MCMI-II = Millon Clinical Multiaxial Inventory (Millon, 1997), GSI = global severity index (Derogatis & Savitz, 2000), MANSA = Manchester Short Assessment for Quality of Life (Priebe et al., 1999), MAAS = mindfulness attention awareness scale (Brown & Ryan, 2003), SMBCT = schema mindfulness based cognitive therapy, COMET = competitive memory therapy, RSES = Rosenberg self-esteem scale (Rosenberg, 1965).

*As no significant group differences, the study’s authors combined conditions for analyses. Authors were contacted for additional information, without response.

Table IV. Assessment of methodological quality for included studies via the MMAT criteria.

	Screening questions		1. Qualitative					2. Quantitative randomized control trials					3. Quantitative non-randomized					4. Quantitative descriptive					5. Mixed Methods
Study	S1	S2	1.1	1.2	1.3	1.4	1.5	2.1	2.2	2.3	2.4	2.5	3.1	3.2	3.3	3.4	3.5	4.1	4.2	4.3	4.4	4.5	5.1	5.2	5.3	5.4	5.5
1	Y	Y	.	.	.	.	.	Y	Y	Y	Y	Y	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.
2	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	N	Y	CT	.	.	.	.	.	.	.	.	.	.
3	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	CT	N	Y	.	.	.	.	.	.	.	.	.	.
4	Y	Y	.	.	.	.	.	Y	Y	Y	N	Y	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.
5	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	Y	Y	Y	.	.	.	.	.	.	.	.	.	.
6	Y	Y	.	.	.	.	.	Y	CT	CT	CT	Y	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.
7	Y	Y	.	.	.	.	.	.	.	.	.	.	CT	Y	CT	Y	Y	.	.	.	.	.	.	.	.	.	.
8	Y	Y	.	.	.	.	.	.	.	.	.	.	CT	Y	CT	Y	Y	.	.	.	.	.	.	.	.	.	.
9	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	Y	Y	Y	.	.	.	.	.	.	.	.	.	.
10	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	N	N	Y	.	.	.	.	.	.	.	.	.	.
11	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	Y	Y	Y	Y	.	.	.	.	.	.	.	.	.	.
12	Y	Y	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	Y	Y	Y	Y	N
13	Y	Y	.	.	.	.	.	.	.	.	.	.	Y	N	N	Y	Y	.	.	.	.	.	.	.	.	.	.
14	Y	Y	.	.	.	.	.	Y	Y	N	CT	Y	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.

Note. Abbreviations: Y = Yes, N = No, CT = Cannot tell. S1 = “Are there clear research questions?” S2 = “Do the collected data allow to address the research questions?” 1.1. = “Is the qualitative approach appropriate to answer the research question?” 1.2. = “Are the qualitative data collection methods adequate to address the research question?” 1.3 = “Are the findings adequately derived from the data?” 1.4. “Is the interpretation of results sufficiently substantiated by data?” 1.5. “Is there coherence between qualitative data sources, collection, analysis and interpretation?” 2.1. = “Is randomization appropriately performed?” 2.2. = “Are the groups comparable at baseline?” 2.3. = “Are there complete outcome data?” 2.4 = “Are outcome assessors blinded to the intervention provided?” 2.5 = “Did the participants adhere to the assigned intervention?” 3.1. = “Are the participants representative of the target population?” 3.2. = “Are measurements appropriate regarding both the outcome and intervention (or exposure)?” 3.3. = “Are there complete outcome data?” 3.4. = “Are the confounders accounted for in the design and analysis?” 3.5. = “During the study period, is the intervention administered (or exposure occurred) as intended?” 4.1. = “Is the sampling strategy relevant to address the research question?” 4.2. = “Is the sample representative of the target population?” 4.3. = “Are the measurements appropriate?” 4.4. = “Is the risk of nonresponse bias low?” 4.5. = “Is the statistical analysis appropriate to answer the research question?” 5.1. = “Is there an adequate rationale for using a mixed methods design to address the research question?” 5.2. = “Are the different components of the study effectively integrated to answer the research question?” 5.3. = “Are the outputs of the integration of qualitative and quantitative components adequately interpreted?” 5.4. = “Are divergences and inconsistencies between quantitative and qualitative results adequately addressed?” 5.5. = “Do the different components of the study adhere to the quality criteria of each tradition of the methods involved?”

*Ratings were conducted in accordance with the Mixed Methods Appraisal Tool (MMAT; Hong et al., 2018).

Figure 1. Study selection process via PRISMA flowchart.

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