Literature Review

To conduct the study searches, two reviewers utilized the Web of Science, PubMed, PsycINFO, and Scopus databases to find articles published in the last five years (2017-2022). The descriptor terms used to create the keywords were based on terms found on the MeSH platform. After several tests, the defined search strategy was as follows: (mindfulness) OR (mindfulness intervention) OR (mindfulness meditation) AND (psychological flexibility) OR (cognitive flexibility) OR (executive functions) OR (self-control) OR (inhibitory control).

Eligibility Criteria

The studies included in the research were randomized controlled trials conducted in the last five years and published in English. The target population comprised adults aged between 18 and 60 years. The mindfulness interventions included in the studies were required to follow established protocols such as Mindfulness-Based Stress Reduction (MBSR), Mindfulness-Based Cognitive Therapy (MBCT), among others.

Methodological Analysis

The online platform CADIMA was used for screening, with article selection performed independently by two researchers in a blinded process. Subsequently, the Risk of Bias Tool (ROB-2) was used to assess the risk of bias.

Data Extraction

For data extraction, a table was created containing descriptive information about the studies, including: the number of participants, mean age range, type of intervention, type of control group, the executive function studied, and main results.

Search Results

After applying the search strategy to the databases, 1,304 articles were identified, of which 225 duplicates were removed. A total of 1,079 articles were screened by title and abstract, resulting in the exclusion of 1,047 articles. Thirty-two articles were assessed through full-text reading, of which 24 were excluded for not using mindfulness practices based on an established protocol, involving participants older than 60 years, or not being randomized studies. For the risk of bias analysis, 8 articles remained. Among these, 6 studies presented a low risk of bias and were included in the final analysis. Figure 1 presents the PRISMA diagram of the study.

General Characteristics of the Studies

All the studies included in the review (^{Alizadehgoradel et al., 2021}; ^{Garland et al., 2019}; ^{Hoxhaj et al., 2018}; ^{Quan et al., 2018}; ^{Zhu et al., 2019}; ^{Zou et al., 2020}) met the criteria of being randomized controlled trials with mindfulness interventions based on an existing protocol (e.g., Mindfulness-Based Stress Reduction - MBSR), involving participants aged 18 to 60 years and presenting a low risk of bias. All studies included either active or passive control groups and evaluated cognitive functions.

Three studies (^{Quan et al., 2018}; ^{Zhu et al., 2019}; ^{Zou et al., 2020}) focused on non-clinical populations, while the other three involved clinical populations: participants with chronic pain (^{Garland et al., 2019}), methamphetamine use disorder (^{Alizadehgoradel et al., 2021}), or adults diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD) (^{Hoxhaj et al., 2018}).

Regarding participants' gender and age, all studies showed baseline distributions without major disparities. Randomization methods ensured balance in terms of age, gender, and other variables between intervention and control groups, resulting in a low risk of bias. Further details about participants' gender distribution and mean age can be found in Table 1.

Figure 1:  PRISMA flowchart 

Table 1: General characteristics of the participants 

^Nota: SD: Standard Deviation; GC: Group Control; MBI: Mindfulness-based Intervention; tDCS: transcranial direct current stimulation; MBSR: Mindfulness-based Stress Reduction; ADHD: Attention Deficit/Hyperactivity Disorder; MORE: Mindfulness-Oriented Recovery Enhancement; MBSAT: Mindfulness-Based Substance Abuse Treatment; MAP: Mindfulness Awareness Practices; MBCT: Mindfulness-Based Cognitive Therapy.

Executive Functions and Mindfulness Interventions

The executive functions analyzed in the reviewed studies included attention (^{Hoxhaj et al., 2018}; ^{Zhu et al., 2019}), cognitive control and inhibition (G^{arland et al., 2019}), executive functions and craving (^{Alizadehgoradel et al., 2021}), executive control and orientation (^{Quan et al., 2018}), and cognitive flexibility (^{Zou et al., 2020}).

The mindfulness interventions were as follows: Mindfulness-Based Stress Reduction (MBSR), lasting 12 weeks (^{Zhu et al., 2019}); Mindfulness-Oriented Recovery Enhancement (MORE), lasting 8 weeks (^{Garland et al., 2019}); Mindfulness-Based Substance Abuse Treatment (MBSAT), lasting 6 weeks with two sessions per week (^{Alizadehgoradel et al., 2021}); Mindfulness Awareness Practices (MAP), lasting 8 weeks (^{Hoxhaj et al., 2018}); Mindfulness-Based Cognitive Therapy (MBCT), lasting 7 days (^{Quan et al., 2018}); and MBSR, lasting 8 weeks (^{Zou et al., 2020}).

Two studies used a waitlist as a passive control group (^{Zhu et al., 2019}; ^{Zou et al., 2020}), while the other studies included active control groups such as support groups (^{Garland et al., 2019}), transcranial direct current stimulation (tDCS), tDCS combined with MBSAT, and placebo (^{Alizadehgoradel et al., 2021}), psychoeducation (^{Hoxhaj et al., 2018}), and relaxation (^{Quan et al., 2018}). Additional details about each intervention can be found in Table 1.

Cognitive Tasks and Instruments Used

The tasks and instruments used in each study are summarized in Table 2. The cognitive tasks used to assess executive functions varied across studies. ^{Zhu et al. (2019}) used the Continuous Performance Test (CPT) to analyze sustained attention and the Stroop Test to evaluate response inhibition.^{Garland et al. (2019}) used the Emotional Go/No-Go task to assess inhibitory responses in the context of negative emotional interference.

^{Alizadehgoradel et al. (2021}) employed the Go/No-Go task for cognitive control, the N-Back Test for working memory, the Wisconsin Card Sorting Test (WCST) to assess prefrontal cortex performance, and the Balloon Analogue Risk Task (BART) to evaluate risk-taking behaviors and decision-making under risk.

^{Hoxhaj et al. (2018}) used the CAARS scale, which includes 8 subscales to evaluate ADHD-related symptoms, including inattention. ^{Quan et al. (2018}) assessed orientation and executive control using the Attention Network Test. ^{Zou et al. (2020}) used the CFI scale, a 20-item Likert-type scale, to evaluate cognitive flexibility.

Effects of Mindfulness on Inhibitory Control, Working Memory, and Cognitive Flexibility

In terms of attention, ^{Zhu et al. (2019}) found that a 12-week MBSR intervention significantly improved sustained attention and positive emotions in the mindfulness group compared to the waitlist control group. Similarly, ^{Hoxhaj et al. (2018}) observed significant improvements in attention and associated ADHD symptoms following an 8-week MAP intervention compared to psychoeducation, with effects persisting after six months (follow-up).

Regarding cognitive control or inhibitory control, both G^{arland et al. (2019}) and ^{Alizadehgoradel et al. (2021}) found significant improvements in the mindfulness groups compared to control groups. For working memory, ^{Alizadehgoradel et al. (2021)} reported significant gains in the MBSAT group compared to the placebo group.

^{Quan et al. (2018}) demonstrated increased responsiveness to orientation and executive control after a 7-day MBCT intervention compared to a relaxation control group. For cognitive flexibility, both clinical (^{Alizadehgoradel et al., 2021}) and non-clinical (^{Zou et al., 2020}) populations showed significant improvements in mindfulness groups compared to controls. These results are summarized in Table 2.

Table 2: Types of interventions and main results 

^Note:ADHD: Attention-deficit/hyperactivity disorder; MBI: Mindfulness-based Intervention); MBSR: Mindfulness-based Stress Reduction; MAP: Mindfulness Awareness Practices; MORE: Mindfulness-Oriented Recovery Enhancement; MBCT: Mindfulness-Based Cognitive Therapy; MBSAT: Mindfulness-Based Substance Abuse Treatment; tDCS: transcranial direct current stimulation.

Description of Protocols Used in the Studies

The interventions in all studies were based on well-established protocols with substantial evidence supporting their mental and physical health benefits for clinical and non-clinical populations. Five different protocols were identified: Mindfulness-Based Stress Reduction (MBSR) (^{Zhu et al., 2019}; ^{Zou et al., 2020}); Mindfulness-Oriented Recovery Enhancement (MORE) (^{Garland et al., 2019}); Mindfulness-Based Substance Abuse Treatment (MBSAT) (^{Alizadehgoradel et al., 2021}); Mindfulness-Based Cognitive Therapy (MBCT) (^{Quan et al., 2018}); and Mindfulness Awareness Practices (MAP) (^{Hoxhaj et al., 2018}).

Further details on each protocol can be found in Table 3. Across the included studies, all protocols demonstrated significant effects on executive functions, with 4 out of 6 studies showing greater benefits in the mindfulness intervention groups compared to control groups.

Table 3: Description of protocols 

^Notes: ¹^{Vibe et al. (2017}); ² ^{Garland (2014}), and Garland and Howard (2013); ³ ^{Himelstein and Saul (2015}), and ^{Alizadehgoradel et al. (2019}); ^{4van der Velden et al. (2015}), and ^{Liberali (2017}); ^{5.Hoxhaj et al. (2018}).

General Characteristics of Participants

The studies included both clinical and non-clinical populations of men and women aged 18 to 60. This age range was chosen as a criterion for this review, given that most studies on executive functions tend to focus on specific developmental stages such as childhood, adolescence, or old age-periods more susceptible to rapid brain changes or cognitive decline (^{Im et al., 2021}).

According to ^{Ferguson et al. (2021}), the 20-60 age range, often overlooked in literature on the subject, presents more significant changes in executive function development or decline than previously thought. These authors analyzed inhibitory control, working memory, cognitive flexibility, and planning across healthy individuals aged 10 to 86, observing that working memory and planning capacities continue to develop after adolescence, while inhibitory control shows a notable decline beginning at age 30 (^{Ferguson et al., 2021}). However, the studies included in this review did not provide significant findings linking a specific age range to better or worse executive function performance.

Both clinical and non-clinical populations showed significant improvements in at least one aspect of executive functions. A recent study by ^{Didehban et al. (2024}) supports this outcome, as the authors reported better effects of a group-based mindfulness and acceptance protocol compared to a waitlist group in participants with anxiety disorders. These results pertain to both anxiety symptoms and executive functions. Notably, the study by ^{Didehban et al. (2024)} was likely excluded from this review because it was published during the preparation of this study and thus fell outside the defined temporal scope. Such findings reinforce the hypothesis that mindfulness-based interventions effectively enhance executive functions, both directly-improving inhibitory control, working memory, and cognitive flexibility-and indirectly, by reducing stress, depression, and other symptoms, thereby improving quality of life (^{Alizadehgoradel et al., 2021}; ^{Garland et al., 2019}; ^{Hoxhaj et al., 2018}; ^{Quan et al., 2018}; ^{Zhu et al., 2019}; ^{Zou et al., 2020}). According to ^{Diamond and Ling (2016}), interventions that act both directly and indirectly are ideal for improving executive functions as they not only train these functions but also mitigate factors that impair them, such as stress and poor sleep quality.

Promising evidence also emerges from comparative interventions like Rational Emotive Behavior Therapy (REBT). ^{Tóth et al. (2023}) observed improvements in competitive anxiety, perfectionism, irrational beliefs, and executive functions (e.g., cognitive flexibility and inhibition) resulting from REBT, while mindfulness interventions primarily improved cognitive flexibility.

The format of the intervention protocol also appears to be a relevant variable. For example, ^{Vieth and von Stockhausen (2023}) observed no differential effects on executive functions in a non-clinical sample when comparing brief mindfulness interventions (three or four sessions focusing on breath mindfulness) with controls such as relaxation training or listening to podcasts. However, none of the studies included in this review employed brief interventions, so this variable was not discussed further.

Protocols Used and Their Effects on Executive Functions

The findings suggest that all mindfulness-based protocols produced benefits for inhibition-related functions, including attention, cognitive control, and inhibitory or executive control (^{Alizadehgoradel et al., 2021}; ^{Garland et al., 2019}; ^{Hoxhaj et al., 2018}; ^{Quan et al., 2018}; ^{Zhu et al., 2019}), in both clinical and non-clinical adult populations. These results align with the literature, which shows extensive evidence of mindfulness practices improving both behavioral and neural aspects of inhibition-related functions. Moreover, these benefits can be maintained for up to five months post-intervention (^{Gallant, 2016}).

Other executive functions also showed improvements, such as working memory and cognitive flexibility (^{Alizadehgoradel et al., 2021}) and orientation (^{Quan et al., 2018}). However, fewer studies have reported significant changes in these functions, a trend consistent with existing literature (^{Cásedas et al., 2020}; ^{Gallant, 2016}; ^{Millett et al., 2021}). This scarcity of evidence might be explained by the fact that these changes are more pronounced in populations with cognitive decline, such as individuals over 65 years old, which might explain the absence of such data in studies on adolescents and young adults (^{Gallant, 2016}).

Limitations and Suggestions for Future Studies

This review aimed to establish clear inclusion criteria to ensure greater methodological and conceptual homogeneity regarding executive functions, assessment methods, participant randomization, intervention models, and other factors. However, despite these efforts, discrepancies in terminologies (e.g., inhibitory control, executive control, cognitive control) were observed among the analyzed studies, potentially leading to varied interpretations depending on the definitions of executive functions employed. This limitation is common in randomized controlled trials on this topic, as well as in systematic reviews and meta-analyses. Future studies should aim for more precise definitions of executive functions to reduce interpretative variability.

Another significant limitation was the lack of detailed operationalization of the mindfulness interventions (e.g., specific session content or main techniques used), hindering the comparability of studies and deeper discussion. Discrepancies in the demographics and cultural contexts of study populations also limited the generalizability of findings. Future research should aim for greater standardization regarding target populations (e.g., cultural and socioeconomic factors) and provide more detailed descriptions of mindfulness protocols (e.g., duration, objectives, main techniques) to facilitate in-depth discussions and correlations between specific protocols or techniques and their effects on executive functions.

Further limitations include variability in tasks and questionnaires used to assess executive functions. While many studies employed well-validated cognitive tasks, some used questionnaires such as the CAARS (^{Hoxhaj et al., 2018}) or CFI (^{Zou et al., 2020}), which may not be sufficient to infer direct changes in executive functions. Future studies should better identify cognitive tasks and questionnaires that most validly assess specific executive functions, ideally using multiple measures for each construct.

Finally, the lack of follow-ups in some studies limited understanding of the long-term effects of mindfulness interventions. Although follow-ups may be challenging in research contexts, they are highly recommended to ensure the reliability and durability of intervention outcomes. Moreover, variability in control groups (e.g., waitlists, psychoeducation, relaxation training) complicates the reliability and generalizability of findings. Defining more effective control group interventions could significantly benefit future research, particularly systematic reviews and meta-analyses.

Future studies should also explore mindfulness interventions delivered via technology (e.g., mobile apps) and their effects on adult executive functions, as mindfulness practices have increasingly incorporated technological formats in recent studies, although research on their impact on executive functions remains limited. Additionally, future research should evaluate the effects of mindfulness interventions on executive functions as a whole rather than focusing primarily on attention and cognitive flexibility. A broader assessment would provide deeper insights into the topic.