© Edizioni Centro Studi Erickson, Trento, 2026 — Counseling

Vol. 19, n. 1, febbraio 2026

doi: 10.14605/CS1912602 — ISSN: 2421-2202 — pp. 23-38

Corrispondenza: Chua Bee Seok — e-mail: chuabs@ums.edu.my

ARTICOLI SU INVITO

Valutare l’inflessibilità psicologica: Validazione dell’Acceptance and Action Questionnaire-II (AAQ-II) in studenti universitari malesi

Chua Bee Seok¹, Walton Wider² e Rosnah Ismail³

Sommario

Nonostante la crescente applicazione di acceptance-based interventions nell’istruzione superiore, le prove empiriche sulle proprietà psicometriche delle misure di inflessibilità psicologica negli studenti universitari malesi rimangono limitate. Questo studio si è posto obiettivo di esaminare l’affidabilità e la validità dell’Acceptance and Action Questionnaire-II (AAQ-II) in studenti universitari malesi. I partecipanti erano studenti universitari reclutati da diverse università in Malesia (N = 550). Le misure somministrate includevano l’inflessibilità psicologica e la fusione cognitiva. L’AAQ-II ha dimostrato un’eccellente coerenza interna (α di Cronbach = .91). L’analisi fattoriale confermativa ha indicato un adattamento del modello da accettabile a buono su più indici. In linea con la teoria dell’Acceptance and Commitment Therapy, l’AAQ-II ha mostrato una forte validità concorrente associandosi positivamente alla fusione cognitiva. Nel complesso, i risultati forniscono un solido supporto empirico all’affidabilità, alla validità strutturale e alla validità concorrente dell’AAQ-II per l’uso con studenti universitari malesi. Questo studio contribuisce alla limitata letteratura psicometrica locale sulle misure basate sull’accettazione nell’istruzione superiore e supporta l’uso dell’AAQ-II sia nella ricerca che nella valutazione della salute mentale degli studenti nel contesto malese.

Parole chiave

Acceptance and Action Questionnaire-II (AAQ-II), inflessibilità psicologica, proprietà psicometriche, studenti universitari malesi, Acceptance and Commitment Therapy, Salute mentale.

INVITED ARTICLES

Evaluating Psychological Inflexibility: Validation of the Acceptance and Action Questionnaire-II (AAQ-II) in Malaysian University Students

Chua Bee Seok⁴, Walton Wider⁵ and Rosnah Ismail⁶

Abstract

Despite the growing application of acceptance-based interventions in higher education, empirical evidence on the psychometric properties of psychological inflexibility measures among Malaysian university students remains limited. This study aimed to examine the reliability and validity of the Acceptance and Action Questionnaire-II (AAQ-II) among Malaysian university students. Participants were undergraduate students recruited from several universities in Malaysia (N = 550). Measures administered included psychological inflexibility and cognitive fusion. The AAQ-II demonstrated excellent internal consistency (Cronbach’s α = .91). Confirmatory factor analysis indicated an acceptable to good model fit across multiple indices. Consistent with acceptance and commitment therapy theory, the AAQ-II demonstrated strong concurrent validity by positively associating with cognitive fusion. Overall, the findings provide robust empirical support for the reliability, structural validity, and concurrent validity of the AAQ-II for use among Malaysian university students. This study contributes to the limited local psychometric literature on acceptance-based measures in higher education and supports the use of the AAQ-II in both research and student mental health assessment within the Malaysian context.

Keywords

Acceptance and Action Questionnaire-II (AAQ-II), Psychological inflexibility, Psychometric properties, Malaysian university students, Acceptance and commitment therapy, Mental health.

Introduction

Psychological inflexibility has become a central construct in contemporary clinical and educational psychology because it is consistently associated with a broad range of mental health difficulties, including anxiety, depression, stress, lower well-being, and poorer academic and psychosocial functioning (Aydin, 2023; Bond et al., 2011; Guo et al., 2022). Within the framework of acceptance and commitment therapy (ACT), psychological inflexibility refers to a rigid pattern of responding to internal experiences, such as thoughts, emotions, and bodily sensations, through experiential avoidance and cognitive fusion in ways that restrict behavior and disrupt engagement in valued life directions (Bond et al., 2011; Wider et al., 2024). Individuals high in psychological inflexibility tend to control, suppress, or avoid distressing internal events, which can paradoxically intensify distress and undermine adaptive functioning (Cervantes-Perea et al., 2025). As psychological demands increase in modern educational environments, particularly in higher education, the accurate conceptualization and measurement of psychological inflexibility have become increasingly important (Levin et al., 2019).

University students are especially vulnerable to psychological inflexibility and its associated negative outcomes. Higher psychological inflexibility has been linked to poorer mental health, lower self-compassion, maladaptive coping, and difficulties in college adjustment (Aydin, 2023; Guo et al., 2022). Academic workload, uncertainty about employment, financial strain, and major social transitions create a developmental context that places sustained demands on students’ emotional regulation and coping capacities (Levin et al., 2019). In Malaysia, these pressures are further shaped by cultural norms emphasizing academic achievement, family expectations, and collectivistic values, which may influence how distress is interpreted, expressed, and managed. Despite increased attention to student mental health in Malaysian higher education, assessment practices often rely on instruments developed and validated in Western contexts, sometimes without adequate evaluation of cultural relevance or psychometric adequacy for local student populations (Mohd Kassim et al., 2021; Taib et al., 2021).

One of the most widely used instruments for assessing psychological inflexibility is the Acceptance and Action Questionnaire-II (AAQ-II). The AAQ-II has been applied across clinical and non-clinical samples and has shown robust associations with anxiety, depression, stress, and general psychological functioning (Bond et al., 2011; Guo et al., 2022). However, accumulating evidence indicates that its psychometric performance can vary across cultural contexts, particularly with respect to factor structure, item functioning, and discriminant validity (Langer et al., 2024; Núñez et al., 2025; Žuljević et al., 2020). Importantly, multiple studies have questioned whether AAQ-II scores may partly reflect general distress or negative affectivity, potentially complicating interpretation when the instrument is used as a process measure in non-clinical samples (Landi et al., 2021; Tyndall et al., 2019; Valencia, 2019). Comparative work also suggests that revised or alternative instruments may demonstrate improved discriminant or incremental validity in some contexts (Fang et al., 2023; Ong et al., 2020). These debates do not negate the utility of the AAQ-II, but they underscore the need for careful, context-specific validation and transparent interpretation of the instrument’s content in a given population.

In Malaysia, empirical evaluations of the AAQ-II among university students remain limited. Existing studies have generally emphasized mental health outcomes rather than systematically establishing the measurement properties of the AAQ-II in educational samples (Mohd Kassim et al., 2021). This gap is notable given cross-cultural evidence that item interpretation and construct representation can vary across languages, cultures, and settings (Žuljević et al., 2020; Langer et al., 2024). Without local psychometric evidence, confidence in research findings is reduced, and it becomes more difficult to use AAQ-II scores for screening, monitoring change, or evaluating ACT-informed interventions in Malaysian higher education.

Accordingly, the present study evaluates the psychometric properties of the AAQ-II among Malaysian university students. Specifically, the study examines its factor structure and internal consistency and tests its concurrent validity by examining associations with cognitive fusion, a theoretically related ACT process (Gillanders et al., 2014; Ong et al., 2019). Given ongoing concerns about the AAQ-II’s discriminant validity, the current validation is positioned as an essential first step in establishing structural adequacy and theory-consistent associations in this population, while also motivating future work to examine measurement invariance and discriminant validity using broader process and symptom measures.

Literature Review

Psychometric Validation of the AAQ-II

The AAQ-II is one of the most widely used self-report instruments for assessing psychological inflexibility and experiential avoidance within the ACT framework. Since its development, the AAQ-II has been evaluated across diverse cultural, linguistic, and clinical contexts. A substantial body of evidence supports its internal consistency, with many studies reporting Cronbach’s alpha values above .80 in both clinical and non-clinical samples (Bond et al., 2011; Eisenbeck & Szabó-Bartha, 2018; Menéndez-Aller et al., 2023; Ruiz et al., 2013). These findings suggest that AAQ-II items tend to function cohesively, although contemporary reporting increasingly recommends supplementing alpha with additional reliability indices when possible.

Regarding structural validity, many studies have supported a unidimensional factor structure, consistent with the AAQ-II’s intended use as a brief global measure of psychological inflexibility. Factor-analytic evidence from samples in Spain, Hungary, Taiwan, Thailand, and Ecuador has frequently supported a single-factor solution with acceptable fit (Chang et al., 2017; Eisenbeck & Szabó-Bartha, 2018; Paladines-Costa et al., 2021; Ruiz et al., 2013; Sumalrot et al., 2022). This pattern supports the practical value of the AAQ-II as a parsimonious instrument for large-scale research and screening contexts.

At the same time, evidence of strict unidimensionality is inconsistent across studies, particularly when advanced psychometric approaches are employed. Item response theory analyses have identified variation in item discrimination and potential differential item functioning, suggesting that some items may be more informative at higher levels of the latent trait (Langer et al., 2024; Ong et al., 2019). Other research has proposed alternative structural representations, including multifactor or bifactor solutions in particular samples (Cho & Seo, 2017; Núñez et al., 2025). These findings do not necessarily invalidate the AAQ-II, but they underscore the methodological necessity of validating the scale within the target population and of interpreting factor-structure findings in relation to sample characteristics, language, and analytic approach.

Concurrent Validity and Conceptual Debates

Evidence for theory-consistent associations of the AAQ-II is well established. Across multiple studies, AAQ-II scores have correlated positively with constructs theoretically linked to psychological inflexibility, including depressive symptoms, anxiety symptoms, stress, psychological distress, and cognitive fusion (Broman-Fulks et al., 2021; Chang et al., 2017; Paladines-Costa et al., 2021; Ruiz et al., 2013). Within ACT models, experiential avoidance and cognitive fusion are tightly linked processes that can jointly contribute to psychological suffering; therefore, strong correlations with cognitive fusion are expected.

However, this pattern of strong associations has also contributed to conceptual debates about discriminant validity. Several studies have argued that the AAQ-II may overlap substantially with general distress or negative affectivity, raising concerns that the measure may partially capture symptom severity rather than a process construct that is separable from distress (Landi et al., 2021; Tyndall et al., 2019; Valencia, 2019). Comparative research suggests that multidimensional psychological flexibility instruments may better differentiate ACT processes from distress and may offer improved conceptual coverage in some contexts (Ong et al., 2020; Rogge et al., 2019). In this sense, AAQ-II validation studies increasingly benefit from examining not only internal consistency and factor structure but also discriminant and incremental validity, particularly in non-clinical samples where negative affectivity may be a strong common factor.

Cross-Cultural Validation and the Malaysian Context

Cross-cultural validation research suggests that the AAQ-II can be meaningfully adapted across diverse settings when rigorous procedures are employed. Evidence for measurement invariance has been reported across demographic and cultural groups in some studies, although partial invariance is also common, especially when comparing clinical and non-clinical samples (Correa-Fernández et al., 2020; Edwards & Vowles, 2020; Spencer et al., 2022). More broadly, the cross-cultural literature indicates that the AAQ-II often demonstrates acceptable reliability and structural validity, but that item functioning and discriminant validity may vary across languages and contexts (Fang et al., 2023; Langer et al., 2024; Žuljević et al., 2020). These findings support a cautious position: the AAQ-II is frequently usable across cultures, but its psychometric properties should not be presumed to transfer without empirical verification.

In Malaysia, psychometric evaluation of the AAQ-II remains limited, particularly in non-clinical educational samples. The Malay version has been validated in clinical populations, with evidence supporting internal consistency, a unidimensional structure, and theory-consistent associations (Shari et al., 2019). By contrast, research involving Malaysian university students has commonly used the AAQ-II as a correlational measure without formally establishing its structural validity, reliability, or invariance across subgroups. For example, Malaysian studies have reported expected associations between AAQ-II scores and related constructs, but have not presented a systematic psychometric evaluation of the scale in student samples (Mohd Kassim et al., 2021). Given the ethnic and linguistic diversity of Malaysian higher education contexts, local validation is particularly important to ensure that AAQ-II scores are interpretable and comparable across subgroups.

Methods

Participants

The final analytic sample consisted of 550 undergraduate students recruited from multiple public and private universities in Malaysia. Participants ranged in age from 18 to 30 years (M = 21.84, SD = 2.31). With respect to gender, 386 participants (70.20%) identified as female and 164 (29.80%) identified as male.

The sample was ethnically diverse. Malay participants constituted 32.00% (n = 176) of the sample. Indigenous ethnic groups from East Malaysia were well represented, including Kadazandusun (23.10%, n = 127), Bajau (9.60%, n = 53), Murut (1.80%, n = 10), Melayu Brunei (5.30%, n = 29), Iban (3.60%, n = 20), and Bidayuh (2.20%, n = 12). Chinese (8.50%, n = 47) and Indian (4.20%, n = 23) participants comprised smaller proportions, while other ethnic groups accounted for 9.60% (n = 53).

Regarding religious affiliation, most participants identified as Muslim (65.60%, n = 361), followed by Christian (25.30%, n = 139), Buddhist (5.10%, n = 28), and Hindu (4.00%, n = 22). In terms of monthly household income, 62.40% (n = 343) reported incomes of RM 4,849 or below, 28.40% (n = 156) reported incomes between RM 4,850 and RM 10,959, and 9.30% (n = 51) reported incomes of RM 10,960 or above.

With respect to academic standing, 54.20% (n = 298) were in their third year of study, followed by second-year students (22.20%, n = 122), fourth-year students (13.50%, n = 74), and first-year students (10.20%, n = 56). Self-rated health status indicated that most participants rated their health as good (38.90%, n = 214) or very good (30.50%, n = 168), whereas 21.30% (n = 117) rated it as excellent. Smaller proportions reported fair (8.4%, n = 46) or poor health (0.90%, n = 5).

Instruments

Acceptance and Action Questionnaire-II (AAQ-II)

Psychological inflexibility was assessed using the Acceptance and Action Questionnaire-II (AAQ-II), a widely used self-report measure grounded in acceptance and commitment therapy (ACT; Bond et al., 2011). The AAQ-II comprises seven items rated on a 7-point Likert scale ranging from 1 (never true) to 7 (always true), with higher scores indicating greater psychological inflexibility, reflecting higher levels of experiential avoidance and cognitive entanglement.

In its original validation, the AAQ-II demonstrated excellent internal consistency, with Cronbach’s alpha values approximating .90, and supported a unidimensional factor structure across multiple clinical and non-clinical samples (Bond et al., 2011). Subsequent studies conducted across diverse cultural contexts have generally replicated these findings, although variability in factor structure and discriminant validity has also been reported in some populations. In the present study, the AAQ-II was administered in English, which is widely used as a medium of instruction in Malaysian higher education. All participants indicated sufficient English proficiency to complete the questionnaire.

Cognitive Fusion Questionnaire (CFQ)

Concurrent validity of the AAQ-II was examined using the Cognitive Fusion Questionnaire (CFQ; Gillanders et al., 2014). The CFQ assesses cognitive fusion, defined as the extent to which individuals become overly entangled with their thoughts and treat them as literal truths that dominate behavior, thereby reducing psychological flexibility.

The present study employed the 7-item single-factor version of the CFQ, which has demonstrated strong psychometric properties across clinical and non-clinical samples (Trindade et al., 2018). Items are rated on a 7-point Likert scale ranging from 1 (never true) to 7 (always true), with higher scores indicating greater cognitive fusion. The CFQ was selected due to its strong theoretical alignment with psychological inflexibility within the ACT framework and its frequent use in validation studies of the AAQ-II.

Data Analysis

Data were analyzed using IBM SPSS Statistics Version 29.0 and IBM SPSS AMOS Version 29.0. Descriptive statistics were computed to summarize demographic characteristics and scale distributions. Prior to inferential analyses, the data were screened for missing values, outliers, and violations of distributional assumptions. Less than 5% of data were missing across items, and listwise deletion was applied for factor analyses.

Confirmatory factor analysis (CFA) was subsequently performed using AMOS to test the unidimensional model. Model estimation was conducted using the maximum likelihood method. Given the ordinal nature of Likert-scale data and the large sample size, model fit was evaluated using multiple complementary indices, including the comparative fit index (CFI), Tucker-Lewis index (TLI), root mean square error of approximation (RMSEA) with 90% confidence intervals, and the chi-square to degrees of freedom ratio (χ²/df). Model fit was interpreted holistically rather than relying on a single cutoff value.

Internal consistency reliability of the AAQ-II was assessed using Cronbach’s alpha. Concurrent validity was evaluated by examining Pearson correlations between AAQ-II and CFQ scores, consistent with theoretical expectations within the ACT framework that higher psychological inflexibility would be associated with greater cognitive fusion.

Results

Confirmatory Factor Analysis

Confirmatory factor analysis (CFA) was subsequently conducted to test the one-factor model of the AAQ-II. The unidimensional model demonstrated an acceptable overall fit to the data. The chi-square statistic was statistically significant, χ²(14) = 81.34, p < .001, which is common in models estimated with large sample sizes. The chi-square-to-degrees-of-freedom ratio was 5.08, slightly exceeding the conventional cutoff of 5.00 but remaining within the range frequently reported in psychometric validation studies.

Incremental fit indices indicated good model fit, with values exceeding recommended thresholds: comparative fit index (CFI = .97), Tucker-Lewis index (TLI = .96), incremental fit index (IFI = .97), normed fit index (NFI = .96), and relative fit index (RFI = .95). Absolute fit indices were also satisfactory, with a goodness-of-fit index (GFI) of .96 and an adjusted goodness-of-fit index (AGFI) of .92.

The root mean square error of approximation (RMSEA) was 0.09, with a 90% confidence interval from 0.07 to 0.11. Although this value slightly exceeded the commonly cited 0.08 criterion, RMSEA values below 0.10 have been considered acceptable in single-factor models with strong theoretical justification and large samples. The root mean square residual (RMR) was low (RMR = .01), further supporting the adequacy of model fit.

Overall, the CFA results shown in Table 1 support the hypothesized unidimensional structure of the AAQ-II among Malaysian university students. All items demonstrated strong and statistically significant standardized factor loadings, indicating that they adequately represent the underlying construct of psychological inflexibility (Figure 1).

Table 1

Confirmatory Factor Analysis Fit Indices for the One-Factor AAQ-II Model

Fit Index	Value	Recommended Cut-off
χ² (df)	81.34 (14)	—
χ²/df	5.08	< 5.00
GFI	.96	≥ .90
AGFI	.92	≥ .90
NFI	.96	≥ .90
RFI	.95	≥ .90
IFI	.97	≥ .90
TLI	.96	≥ .90
CFI	.97	≥ .90
RMR	.01	≤ .08
RMSEA	.09	≤ .10

Note. χ² = chi-square; df = degrees of freedom; GFI = Goodness-of-Fit Index; AGFI = Adjusted Goodness-of-Fit Index; NFI = Normed Fit Index; RFI = Relative Fit Index; IFI = Incremental Fit Index; TLI = Tucker-Lewis Index; CFI = Comparative Fit Index; RMR = Root Mean Square Residual; RMSEA = Root Mean Square Error of Approximation.

Figure 1

Path Diagram of the One-Factor AAQ-II Model Tested Using Confirmatory Factor Analysis (n = 550).

Reliability of the AAQ-II

The AAQ-II demonstrated excellent internal consistency in the present study. Cronbach’s alpha for the total scale was 0.91, indicating high reliability for assessing psychological inflexibility among Malaysian university students.

Concurrent Validity of the AAQ-II

Concurrent validity of the AAQ-II was examined through its association with the CFQ. Within the ACT framework, higher levels of cognitive fusion are theoretically associated with greater psychological inflexibility, as individuals become excessively entangled with their thoughts, thereby constraining flexible and value-consistent behavior.

As expected, the results revealed a strong and statistically significant positive correlation between AAQ-II and CFQ scores (r = .78, p < .001). This finding indicates that higher psychological inflexibility was associated with greater cognitive fusion, reflecting a stronger dominance of thoughts over actions. The magnitude and direction of this association are consistent with prior empirical findings and provide robust support for the concurrent validity of the AAQ-II within this Malaysian university student sample.

Discussion

The present study evaluated the psychometric properties of the AAQ-II among Malaysian university students by examining its factor structure, internal consistency reliability, and concurrent validity with cognitive fusion. Overall, the findings provide clear empirical support for the AAQ-II as a reliable and structurally coherent measure of psychological inflexibility in this population. The results align with the study’s objectives and contribute to the literature by addressing a notable gap in the local validation of ACT-based measures in Malaysian higher education.

Consistent with the theoretical conceptualization of psychological inflexibility as a global construct within ACT, the confirmatory factor analyses supported a unidimensional structure of the AAQ-II. All seven items loaded strongly on a single latent factor, and the model demonstrated an acceptable overall fit across multiple indices. These findings are broadly consistent with international validation studies that have reported a stable one-factor structure of the AAQ-II across diverse cultural and educational contexts, including samples from Asia, Europe, and Latin America (Bond et al., 2011; Chang et al., 2017; Eisenbeck & Szabó-Bartha, 2018; Sumalrot et al., 2022). Importantly, the present results suggest that the core construct of psychological inflexibility, as operationalized by the AAQ-II, is meaningfully represented among Malaysian university students despite potential cultural differences in emotional expression, coping norms, and help-seeking behaviors. This finding supports the conceptual coherence of the AAQ-II and reinforces its suitability as a brief instrument for assessing psychological inflexibility in non-clinical student populations.

The AAQ-II also demonstrated excellent internal consistency in the present study, with a Cronbach’s alpha coefficient exceeding .90. This level of reliability is consistent with prior validation research conducted in both clinical and non-clinical samples and indicates that the scale items function cohesively in assessing a single underlying construct (Bond et al., 2011; Menéndez-Aller et al., 2023). The strong internal consistency observed in this Malaysian student sample is noteworthy, given ongoing concerns in the literature regarding potential cultural variability in item interpretation. While reliability alone does not guarantee construct validity, the present findings suggest that the AAQ-II demonstrates robust internal consistency in this educational and cultural context.

Evidence for concurrent validity was provided by the strong positive association observed between AAQ-II scores and cognitive fusion. Within the ACT framework, cognitive fusion and experiential avoidance are theoretically linked processes that jointly contribute to psychological inflexibility. As expected, higher levels of psychological inflexibility were associated with greater cognitive fusion, reflecting a tendency for individuals to become overly entangled with their thoughts and to experience reduced behavioral flexibility. This pattern is highly consistent with prior research demonstrating substantial correlations between the AAQ-II and measures of cognitive fusion across diverse samples (Broman-Fulks et al., 2021; Chang et al., 2017; Ruiz et al., 2013). The magnitude of the association observed in the present study reinforces the convergent and concurrent validity of the AAQ-II as an indicator of core ACT processes among Malaysian university students.

At the same time, the strength of the association between the AAQ-II and cognitive fusion warrants cautious interpretation in light of ongoing conceptual debates regarding the discriminant validity of the AAQ-II. Previous studies have raised concerns that the AAQ-II may overlap substantially with general psychological distress or negative affectivity, potentially limiting its ability to distinguish process-based constructs from symptom severity (Landi et al., 2021; Tyndall et al., 2019). Although the present study did not directly assess discriminant validity against symptom-based measures, the observed association with cognitive fusion is theoretically expected and consistent with ACT theory. Nevertheless, future research in Malaysian student populations should incorporate additional process-based and symptom-based measures to more comprehensively evaluate the discriminant and incremental validity of the AAQ-II.

Conclusion

Psychological inflexibility represents a core process underlying a wide range of mental health difficulties among university students, yet its accurate assessment remains challenging in non-Western and educational contexts. In Malaysia, student mental health research has increasingly drawn on ACT-based constructs, but empirical validation of key measurement instruments has not kept pace with their widespread application. The lack of a rigorously validated measure of psychological inflexibility for Malaysian university students has limited confidence in existing findings and constrained the development and evaluation of culturally responsive interventions. Addressing this methodological gap was the primary motivation of the present study.

The findings provide consistent evidence of the psychometric adequacy of the AAQ-II in a large, ethnically diverse sample of Malaysian university students. The confirmatory factor analyses supported a unidimensional factor structure, aligning with the theoretical conceptualization of psychological inflexibility as a global construct within the ACT framework. All items demonstrated strong factor loadings, and the model exhibited an acceptable overall fit. In addition, the AAQ-II showed excellent internal consistency, indicating that the scale functions cohesively in assessing psychological inflexibility in this population. Concurrent validity was further supported by the strong positive association between AAQ-II scores and cognitive fusion, a theoretically related ACT process.

These findings have important implications for research and practice. Methodologically, the results provide empirical justification for the use of the AAQ-II in Malaysian higher education research, enabling more confident assessment of psychological inflexibility in student populations. Theoretically, the observed alignment between psychological inflexibility and cognitive fusion supports the applicability of ACT process models within collectivistic and culturally diverse educational contexts. In practice, the availability of a validated measure enables educators, counselors, and researchers to more accurately identify students at risk, monitor relevant psychological processes, and evaluate the effectiveness of ACT-informed interventions aimed at enhancing student well-being and psychological flexibility.

Several limitations should be acknowledged. The cross-sectional design precludes conclusions regarding temporal stability, causality, or sensitivity to change. Longitudinal research is needed to examine test–retest reliability and responsiveness of the AAQ-II, particularly in intervention contexts. The reliance on self-report measures may also introduce response biases, including social desirability and culturally shaped response tendencies. Additionally, although the sample was ethnically diverse, measurement invariance across gender, ethnicity, and academic subgroups was not examined and warrants attention in future research.

Future studies should extend this work by testing measurement invariance across key demographic groups, examining predictive and incremental validity relative to symptom-based measures, and evaluating the scale’s sensitivity to change in longitudinal and intervention designs. Comparative research incorporating multidimensional measures of psychological flexibility may further clarify ongoing debates regarding discriminant validity while preserving the practical utility of brief instruments such as the AAQ-II.

In conclusion, this study provides robust evidence that the Acceptance and Action Questionnaire-II is a reliable and structurally valid measure of psychological inflexibility among Malaysian university students. By establishing its psychometric adequacy in this context, the study strengthens the methodological foundation of student mental health research in Malaysia and supports the broader application of ACT-based frameworks in culturally diverse higher education settings.

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1. ¹ Facoltà di Psicologia e Lavoro Sociale, Universiti Malaysia Sabah, Kota Kinabalu, Malesia.

2. ² Facoltà di Economia e Comunicazione, INTI International University, Nilai, Malesia.

3. ³ Università di Cyberjaya, Sepang, Malesia.

4. ⁴ Faculty of Psychology and Social Work, Universiti Malaysia Sabah, Kota Kinabalu, Malaysia.

5. ⁵ Faculty of Business and Communications, INTI International University, Nilai, Malaysia.

6. ⁶ University of Cyberjaya, Sepang, Malaysia.

© Edizioni Centro Studi Erickson, Trento, 2026 — Counseling

Vol. 19, Issue 1, February 2026

doi: 10.14605/CS1912602 — ISSN: 2421-2202 — pp. 23-38

Correspondence: Chua Bee Seok — e-mail: chuabs@ums.edu.my