Combining mindfulness and cognitive training in children with attention deficit hyperactivity disorder: study protocol of a pilot randomized controlled trial (the NeuroMind study).

Introduction: Attention Deficit Hyperactivity Disorder (ADHD) has a global mean prevalence of 5%. Cognitive Training (CT) and Mindfulness-Based Interventions (MBIs) have shown promising results in managing ADHD symptoms, but they are not its Treatment-As-Usual (TAU). The NeuroMind Study aims to evaluate the preliminary effectiveness and feasibility of three interventions: Mindfulness for Health (M4H), CT using the NeuronUP® platform (CT), and a combination of both, Mindfulness Cognitive Training (MCT). There is empirical evidence supporting the effectiveness of the M4H and NeuronUP® platform; however, this study explores for the first time the effectiveness of MCT and CT, as well as the integration of M4H into TAU. The objectives of this 5-month Randomized Controlled Trial (RCT) are: (1) To analyze the preliminary effectiveness and feasibility of M4H, CT or a combination of both (MCT) added to TAU for children with ADHD; (2) To evaluate the role of psychological process variables (mindfulness and emotional regulation) as mediators of 5-month follow-up clinical outcomes; (3) To preliminarily explore whether specific sociodemographic and clinical characteristics can predict the short-and medium-term clinical response to the specific treatments. Methods and analysis: Participants will be 120 children (7 to 12 years) with ADHD recruited at Child and Adolescent Mental Health Service (CAMHS) Sant Joan de Déu Terres de Lleida (Spain) randomly allocated to one of the four study arms: TAU vs. TAU + CT vs. TAU + M4H vs. TAU + MCT. An assessment to collect ADHD symptoms, Executive Functions (EF), comorbid symptoms and global functioning will be conducted pre-intervention, post-intervention (2 months after baseline) and at the 5-month follow-up. Linear mixed models and mediational models will be computed. Discussion: If the preliminary effectiveness and feasibility of the MCT are demonstrated, this study could be a preliminary basis to do a full RCT with a larger sample to definitively validate the intervention. The MCT could be applied in clinical practice if it is definitively validated.Clinical trial registration:ClinicalTrials.gov, identifier, NCT05937347. https://clinicaltrials.gov/study/NCT05937347?locStr=Spain&country=Spain&cond=ADHD&intr=Mindfulness&rank=1.

The Toronto Mindfulness Scale and the State Mindfulness Scale: psychometric properties of the Spanish versions.

Objectives: The Toronto Mindfulness Scale (TMS) and the State Mindfulness Scale (SMS) are two relevant self-report measures of state mindfulness. The purpose of this study was to examine the internal structure and to offer evidence of the reliability and validity of the Spanish versions of the TMS and SMS. Methods: Data from six distinct non-clinical samples in Spain were obtained. They responded to the TMS (n = 119), SMS (n = 223), and measures of trait mindfulness, decentering, non-attachment, depression, anxiety, stress, positive and negative affect, self-criticism, and self-reassurance. The internal structure of the TMS and SMS was analyzed through confirmatory factor analysis. Reliability, construct validity, and sensitivity to change analyses were performed. Results: The correlated two-factor structure (curiosity and decentering) was the best-fitting model for the TMS (CFI = 0.932; TLI = 0.913; RMSEA = 0.100 [0.077-0.123]; WRMR = 0.908). The bifactor structure (general factor, mindfulness of body, and mindfulness of mind) was the best-fitting model for the SMS (CFI = 0.961; TLI = 0.950; RMSEA = 0.096 [0.086-0.106]; WRMR = 0.993). Adequate reliability was found for both measures. The reliability of the SMS specific factors was very poor when controlling for the general factor. The patterns of correlations were mainly as expected and according to previous literature. The TMS and SMS have been able to detect state mindfulness changes after different meditation practices. Conclusion: Validity evidence is provided to support the use of the TMS and SMS in Spanish populations, though the reliability of the SMS specific factors merit revision.

Meditators' Non-academic Definition of Mindfulness.

Objectives: Mindfulness has been defined differently in academic scientific contexts and in Buddhist academic contexts. An under-studied area is that of lay (non-academic) theories of mindfulness. The goal of this article is to identify, organize, analyze in detail, and provide themes from the meditators' definitions of mindfulness. Possible differences and similarities of the collected definitions of mindfulness with the scientific-academic definitions and with the academic-Buddhist definitions are also checked. Methods: A qualitative and inductive thematic analysis on the definitions of mindfulness offered by the participants was carried out. Results: The sample consisted of 326 meditators who offered a definition of mindfulness through an open question. Seven themes were identified: (1) mindfulness defined as attention/awareness; (2) mindfulness defined as a non-evaluative attitude; (3) mindfulness defined as strategy; (4) mindfulness defined from a theoretical analysis; (5) mindfulness defined as a psycho-affective-spiritual state; (6) mindfulness defined as personal development; and (7) lack of understanding of mindfulness. From these themes, it can be deduced that the definitions collected share more patterns of meaning with the scientific-academic definition of mindfulness than with the academic-Buddhist one. Conclusions: The findings of this study provide new insights into the complexity and heterogeneity of the definition of mindfulness. What has been discovered may indicate the complexity of the mindfulness construct itself. Supplementary Information: The online version contains supplementary material available at 10.1007/s12671-022-01899-3.

A Functional Connectivity Study to Investigate the Role of the Right Anterior Insula in Modulating Emotional Dysfunction in Borderline Personality Disorder.

OBJECTIVE: Previous imaging studies in patients with borderline personality disorder (BPD) have detected functional brain dysfunctions. Mindfulness training may improve the symptoms of BPD, although the neural mechanisms involved remain poorly understood. This study had several key aims: a) to investigate the role of right anterior insula (rAI) functional connectivity in modulating baseline emotional status in BPD, b) to compare differences in connectivity changes after mindfulness training versus interpersonal effectiveness intervention, and c) to explore the correlation between longitudinal changes in imaging data and clinical indicators. METHODS: Thirty-eight patients with BPD underwent resting-state functional magnetic resonance imaging. Participants completed self-report clinical scales and participated in a dialectical-behavioral therapy (mindfulness versus interpersonal effectiveness modules). Changes in clinical and imaging variables were evaluated longitudinally after completion of the first 10-week sessions of psychotherapeutic intervention. RESULTS: At baseline, the rAI was strongly connected with the other salience network nodes and anticorrelated with most core nodes of the default mode network (p < .05, corrected). The functional connectivity of the rAI correlated with emotional dysregulation and deficits in mindfulness capacities (p < .05, corrected). After completion of psychotherapeutic intervention, both groups (mindfulness and interpersonal effectiveness) showed divergent posttherapy functional connectivity changes, which were in turn associated with the clinical response. CONCLUSIONS: The functional connectivity of the rAI seems to play an important role in emotion dysregulation and deficits in mindfulness capacities in individuals with BPD. Psychotherapy seems to modulate this functional connectivity, leading to beneficial changes in clinical variables.

Ayahuasca may help to improve self-compassion and self-criticism capacities.

OBJECTIVE: Ayahuasca is a psychedelic brew that originated in the Amazon basin. The psychological effects of this drug are becoming better understood due to the growing research interest in identifying new potential therapeutic agents for the treatment of emotion dysregulation and other disorders. Previous studies suggest that ayahuasca enhances mindfulness-related capacities (decentering, non-judging, non-reacting and acceptance) and emotion regulation. The aim of the present exploratory study was to determine the effects of ayahuasca on self-compassion in a community sample. METHODS: We administered validated questionnaires (the Self-Compassion Scale-Short Form and Forms of Self-Criticism and Self-Reassurance) to evaluate pre-post changes in self-compassion and self-criticism/self-reassurance in 45 volunteers (27 women; 60%) before and after (≤24 h) an ayahuasca ceremony. Most participants (n = 29; 67.4%) had previously used ayahuasca. RESULTS: Ayahuasca resulted in significant improvements, with medium to large effect sizes (η2  = 0.184-0.276), in measures of self-compassion (p < 0.05), self-criticism (p < 0.01) and self-reassurance (p < 0.01). CONCLUSIONS: The findings of this study suggest that ayahuasca promotes well-being and self-compassion, which could have a therapeutic effect on individuals with negative affect and other psychopathological conditions. Large, controlled studies are needed to confirm these findings.

Mindfulness in Borderline Personality Disorder: Decentering Mediates the Effectiveness.

BACKGROUND: Mindfulness skills training is a core component of dialectical behavior therapy (DBT) that has proven to be an effective stand-alone treatment for the general symptoms commonly present in patients with borderline personality disorder (BPD). The aim of the present study was to compare the effectiveness of mindfulness-based DBT skills training (DBT-M) to interpersonal effectiveness-based DBT skills training (DBT-IE) in reducing BPD symptoms. We also evaluated the specific mechanism of action of these therapies through two proposed mediators: decentering and emotion dysregulation. METHOD: A total of 102 participants diagnosed with BPD were included in the study. Multivariate repeated-measures ANOVAs were performed followed by a multiple mediation analysis. RESULTS: The analyses showed that DBT-M was more effective than DBT-IE in reducing BPD symptoms, although both interventions were effective in reducing emotion dysregulation. We identified a serial mediation model in which DBT-M reduced BPD symptoms by increasing decentering ability, which in turn reduced emotion dysregulation. This mediation effect showed that changes in decentering preceded improvements in emotion dysregulation. CONCLUSIONS: These findings underscore the key role of decentering as a primary mechanism of action in DBT-M, suggesting that this skill is a main component for BPD treatment.

Stable isotope evidence of human diet in Mediterranean context during the Last Glacial Maximum.

The Final Gravettian in Europe overlapped with the cold and dry climatic event of Heinrich 2 (ca. 27-23.5 kyr cal BP), which caused the contraction of human distribution over refuge regions in the southern peninsulas of Europe. Here, we consider the human subsistence in the northeast Iberian Peninsula, where an extensive range of small to large prey was available. Four human remains from the Serinyà caves were investigated using the stable isotope ratios of carbon, nitrogen, and sulfur of bulk collagen (δ13Ccoll, δ15Ncoll, δ34Scoll) and of phenylalanine and glutamine amino acids (δ15NPhe, δ15NGlu). Direct AMS dating of the human and animal remains from the Final Gravettian levels of Mollet III, Reclau Viver, and Arbreda at Serinyà confirmed their chronological position from 27.5 to 22.6 kyr cal BP and the occurrence of four different human individuals. The δ13Ccoll and δ15Ncoll values showed a large contribution of terrestrial prey to the dietary protein of the individuals. The δ34Scoll values were consistent with a subsistence based on the local continental resources, without detectable contribution of marine resource. The δ15NPhe and δ15NGlu values confirm that freshwater resources were not a substantial component of the diet of the considered individuals. Contrast in the isotopic amounts in bulk collagen could be interpreted as the result of different proportions of terrestrial prey in human diet at Serinyà. Altogether, the isotopic investigation reveals the importance of terrestrial over aquatic resources in the subsistence of the studied Final Gravettian individuals from the Serinyà caves in northeastern Iberia during the Last Glacial Maximum. It would be consistent with a scenario of a productive enough terrestrial ecosystem to sustain hunter-gatherer subsistence in this refuge region.

Corrigendum: Psychological Effects of a 1-Month Meditation Retreat on Experienced Meditators: The Role of Non-attachment.

[This corrects the article DOI: 10.3389/fpsyg.2016.01935.].

Corrigendum: Four Weekly Ayahuasca Sessions Lead to Increases in "Acceptance" Capacities: A Comparison Study with a Standard 8-Week Mindfulness Training Program.

[This corrects the article DOI: 10.3389/fphar.2018.00224.].

Effects of mindfulness training on the default mode network in borderline personality disorder.

Patients with borderline personality disorder (BPD) present dysfunctions of the default mode network (DMN). Mindfulness training has proven effective to improve the symptoms of BPD. The present study examines the effect of mindfulness training on BPD symptomatology and DMN activity during the performance of a working memory task in patients with BPD. Sixty-five individuals with BPD were randomized to receive psychotherapy with either the mindfulness module of dialectical behavioural therapy (DBT-M) or with interpersonal effectiveness module (DBT-IE). The impact of treatments was evaluated with clinical and mindfulness variables as well as with functional magnetic resonance imaging during performance of the task. Both groups showed improvement in BPD symptoms and other clinical variables after treatment. Unexpectedly, there were no between-group differences in DMN activation or deactivation. However, activation of the left anterior insula increased in both groups after the intervention. Compared with the control group, participants in the DBT-M group presented higher deactivation in a cluster extending bilaterally from the calcarine to the cuneus and superior occipital gyri.

Religiosity and Meditation Practice: Exploring Their Explanatory Power on Psychological Adjustment.

There has been increased interest in the relationships between religiosity, meditation practice and well-being, but there is lack of understanding as to how specific religious components and distinct meditation practices could influence different positive and negative psychological adjustment outcomes. The aim of this study was to assess the explanatory power of religious beliefs and the practice of prayer, focused attention (FA), open monitoring (OM), and compassion meditation (CM) on psychological adjustment, taking into consideration a number of practice-related variables such as session length, frequency of practice and lifetime practice. Psychological adjustment was assessed by means of happiness, positive affect, depression, negative affect, and emotional overproduction. A cross-sectional design was used, with a final sample comprising 210 Spanish participants who completed an online assessment protocol. Hierarchical regressions were performed, including age, sex and psychotropic medication use in the first step as possible confounders, with the addition of religious beliefs and the practice of prayer, FA, OM, and CM in the second step. FA session length was related to all psychological adjustment outcomes: happiness (ΔR 2 = 0.09, p = 0.002; ß = 0.25, p = 0.001), positive affect (ΔR 2 = 0.09, p = 0.002; ß = 0.18, p = 0.014), depression (ΔR2 = 0.07, p = 0.004; ß = -0.27, p < 0.001), negative affect (ΔR 2 = 0.08, p = 0.007; ß = -0.27, p < 0.001) and emotional overproduction (ΔR 2 = 0.07, p = 0.013; ß = -0.23, p = 0.001). CM session length was related to positive affect (ß = 0.18, p = 0.011). CM practice frequency was associated with happiness (ΔR 2 = 0.06, p = 0.038; ß = 0.16, p = 0.041). Lifetime practice of FA was related to happiness (ΔR 2 = 0.08, p = 0.007; ß = 0.21, p = 0.030) and OM to emotional overproduction (ΔR 2 = 0.08, p = 0.037; ß = -0.19, p = 0.047). Religious beliefs and prayer seemed to be less relevant than meditation practices such as FA, OM, and CM in explaining psychological adjustment. The distinct meditation practices might be differentially related to distinct psychological adjustment outcomes through different practice-related variables. However, research into other forms of institutional religiosity integrating social aspects of religion is required.

Acceptance and present-moment awareness in psychiatric disorders: Is mindfulness mood dependent?

The aim of the present study was to determine 1) whether deficits in two mindfulness dimensions (present-centered awareness and acceptance) were present in individuals with different psychiatric conditions and 2) whether co-existing depressive symptoms affected the mindfulness-related capacities in these groups. A total of 246 individuals, both clinical and non-clinical participants, were included in this study. The clinical sample consisted of 162 individuals; of these, 43 had a diagnosis of cocaine dependence while the remaining 119met clinical criteria for eating disorders (n = 43), major depressive disorder in remission (n = 39), and borderline personality disorder (n = 45). A non-clinical (NC) community sample consisting of 76 individuals was included as a control group. All participants completed self-report instruments to assess present-centered awareness, acceptance, and depressive symptoms. Present-centered awareness scores were significantly associated with depressive symptoms but not with the diagnostic group. By contrast, a significant effect of depressive symptoms and diagnostic group was associated with acceptance scores, with all clinical groups presenting significantly lower scores than the NC sample. These findings suggest that the association between psychopathology, mindfulness, and depressive symptoms varies depending on the specific aspect of mindfulness aspect (i.e., awareness or acceptance) evaluated.

Ayahuasca improves emotion dysregulation in a community sample and in individuals with borderline-like traits.

BACKGROUND: Research suggests that mindfulness-based interventions may improve mindfulness-related capacities (e.g., decentering, non-judging, and non-reacting) and emotion regulation. Previously, our group reported that ayahuasca could be a potential analogue of mindfulness practice. The main aim of the current study was to examine the effects of ayahuasca on emotional regulation and mindfulness-related capacities. Secondarily, we sought to explore the effects of ayahuasca on individuals with borderline personality disorder (BPD) traits. METHOD: This is an observational study of 45 volunteers who participated in an ayahuasca session. The volunteers completed various self-report instruments designed to measure emotional dysregulation (Difficulties in Emotion Regulation Scale (DERS)) and mindfulness traits (Five Facet Mindfulness Questionnaire (FFMQ)-Short Form and Experiences Questionnaire (EQ)) prior to and 24 h after the ayahuasca session. The volunteers were divided into two subgroups based on their score on the McLean Screening Instrument for BPD (MSI-BPD). Twelve participants were grouped into the BPD-like traits subgroup while the rest of them were included in the non-BPD-like subgroup. We performed within-subjects and between-group analyses. RESULTS: Overall, the participants showed significant improvements on the FFMQ subscales observing, acting with awareness, non-judging, and non-reacting and also significantly improved on decentering (EQ scale) and on the DERS subscales emotional non-acceptance, emotional interference, and lack of control. The BPD-like subgroup also showed significant improvements on the DERS subscales emotional interference and lack of control but not in mindfulness capacities. CONCLUSIONS: These findings suggest a potential therapeutic effect for ayahuasca in emotion regulation and mindfulness capacities (including decentering, acceptance, awareness, and sensitivity to meditation practice). Based on these results, we believe that ayahuasca therapy could be of value in clinical populations, such as individuals with BPD, affected by emotion dysregulation.

Correction to: Exploring the relation between childhood trauma, temperamental traits and mindfulness in borderline personality disorder.

In the original publication of this article [1] the funding acknowledgement for grant "PI13/00134, ERDF Funds" was missing.

Relationship between effortful control and facets of mindfulness in meditators, non-meditators and individuals with borderline personality disorder.

As dimensions of effortful control (EC), activation control, attentional control, and inhibitory control could mediate the relationship between mindfulness meditation practice and the facets of mindfulness (i.e., observing, describing, acting with awareness, non-judging and non-reacting to inner experience). In this study, we tested whether participant status: meditators (n = 330), healthy non-meditators (n = 254) and individuals with borderline personality disorder (BPD) diagnosis (n = 46) predicted the facets of mindfulness and if these potential effects were mediated through the three effortful control (EC) dimensions (activation, attentional and inhibitory control). Meditators scored higher than non-meditators on attentional and inhibitory control and on the facets of mindfulness with attentional and inhibitory control partially mediating this relationship between meditation status and mindfulness facets. Participants with BPD showed lower scores on EC along with lower scores on the facets of mindfulness compared with healthy non-meditators. All three aspects of EC partially mediated the relationship between BPD and mindfulness facets. Copyright © 2018 John Wiley & Sons, Ltd.

Four Weekly Ayahuasca Sessions Lead to Increases in "Acceptance" Capacities: A Comparison Study With a Standard 8-Week Mindfulness Training Program.

Background: The therapeutic effects of the Amazonian plant tea ayahuasca may relate to its ability to enhance mindfulness capacities. Ayahuasca induces a modified state of awareness through the combined action of its active principles: the psychedelic N,N-dimethyltryptamine (DMT) and a series of centrally acting ß-carbolines, mainly harmine and tetrahydroharmine. To better understand the therapeutic potential of ayahuasca, here we compared the impact on mindfulness capacities induced by two independent interventions: (a) participation in four ayahuasca sessions without any specific purpose related to improving mindfulness capacities; and (b) participation in a standard mindfulness training course: 8 weeks mindfulness-based stress reduction (MBSR), with the specific goal of improving these skills. Methods: Participants of two independent groups completed two self-report instruments: The Five Facet Mindfulness Questionnaire (FFMQ) and the Experiences Questionnaire (EQ). The MINDSENS Composite Index was also calculated, including those EQ and FFMQ items that have proven to be the most sensitive to meditation practice. Group A (n = 10) was assessed before and after the last of four closely spaced consecutive ayahuasca sessions. Group B (n = 10) was assessed before and after completion of a standard 8-week MBSR course. Results: MBSR training led to greater increases in overall mindfulness scores after the 8-week period. MBSR but not ayahuasca led to increases in the MINDSENS Composite Index. However, the ayahuasca sessions induced comparable increases in the Non-Judging subscale of the FFMQ, specifically measuring "acceptance." Improving this capacity allows for a more detached and less judgmental stance toward potentially distressing thoughts and emotions. Results: The present findings suggest that a small number of ayahuasca sessions can be as effective at improving acceptance as more lengthy and costly interventions. Future studies should address the benefits of combining ayahuasca administration with mindfulness-based interventions. This will allow us to investigate if ayahuasca will improve the outcome of psychotherapeutic interventions.

Psychological variables implied in the therapeutic effect of ayahuasca: A contextual approach.

Ayahuasca is a psychedelic decoction originating from Amazonia. The ayahuasca-induced introspective experience has been shown to have potential benefits in the treatment of several pathologies, to protect mental health and to improve neuropsychological functions and creativity, and boost mindfulness. The underlying psychological processes related to the use of ayahuasca in a psychotherapeutic context are not yet well described in the scientific literature, but there is some evidence to suggest that psychological variables described in psychotherapies could be useful in explaining the therapeutic effects of the brew. In this study we explore the link between ayahuasca use and Decentering, Values and Self, comparing subjects without experience of ayahuasca (n = 41) with subjects with experience (n = 81). Results confirm that ayahuasca users scored higher than non-users in Decentering and Positive self, but not in Valued living, Life fulfillment, Self in social relations, Self in close relations and General self. Scores in Decentering were higher in the more experienced subjects (more than 15 occasions) than in those with less experience (less than 15 occasions). Our results show that psychological process variables may explain the outcomes in ayahuasca psychotherapy. The introduction of these variables is warranted in future ayahuasca therapeutic studies.

Economic Impact of Third-Wave Cognitive Behavioral Therapies: A Systematic Review and Quality Assessment of Economic Evaluations in Randomized Controlled Trials.

The term third-wave cognitive behavioral therapy (CBT) encompasses new forms of CBT that both extend and innovate within CBT. Most third-wave therapies have been subject to randomized controlled trials (RCTs) focused on clinical effectiveness; however, the number and quality of economic evaluations in these RCTs has been unknown and may be few. Evidence about efficiency of these therapies may help support decisions on efficient allocation of resources in health policies. The main aim of this study was to systematically review the economic impact of third-wave therapies in the treatment of patients with physical or mental conditions. We conducted a systematic literature search in PubMed, PsycINFO, EMBASE, and CINALH to identify economic evaluations of third-wave therapies. Quality and Risk of Bias (RoB) assessment of economic evaluations was also made using the Drummond 35-item checklist and the Cochrane Collaboration's tool for assessing risk of bias, respectively. Eleven RCTs were included in this systematic review. Mindfulness-Based Cognitive Therapy (MBCT), Mindfulness-Based Stress Reduction (MBSR), Acceptance and Commitment Therapy (ACT), Dialectical Behavior Therapy (DBT), and extended Behaviour Activation (eBA) showed acceptable cost-effectiveness and cost-utility ratios. No study employed a time horizon of more than 3 years. Quality and RoB assessments highlight some limitations that temper the findings. There is some evidence that MBCT, MBSR, ACT, DBT, and eBA are efficient from a societal or a third-party payer perspective. No economic analysis was found for many third-wave therapies. Therefore, more economic evaluations with high methodological quality are needed.

Direct experience while eating: Laboratory outcomes among individuals with eating disorders versus healthy controls.

OBJECTIVE: To compare individuals with eating disorders (EDs) to healthy controls (HCs) to assess for differences in direct engagement in the eating process. METHOD: Participants (n=58) were asked to eat an orange slice. To assess the degree of direct engagement with the eating process, participants were asked to write down 10 thoughts about the experience of eating the orange slice. Next, the participants were instructed to classify the main focus of each thought as either experiential ("direct experience") or analytical ("thinking about"). A direct experience index (DEI) was computed by dividing the number of times that participants classified an experience as a "direct experience" (the numerator) by the total number of all observations (i.e., direct experience+thinking about). Participants also completed the Five Facet Mindfulness Questionnaire (FFMQ) and the Experiences Questionnaire (EQ) to assess mindfulness facets and decentering, respectively. RESULTS: Compared to controls, participants in the EDs group presented significantly lower levels of direct experience during the eating task (EDs group: mean=43.54, SD=29.64; HCs group: mean=66.17, SD=22.23, p=0.03). Participants in the EDs group also scored significantly lower on other mindfulness-related variables. DISCUSSION: These findings suggest that engagement with the direct experience of eating is lower in individuals with EDs. Future research should investigate the role of mindfulness-based interventions to address direct experience while eating in individuals with EDs.

Unwanted effects: Is there a negative side of meditation? A multicentre survey.

OBJECTIVES: Despite the long-term use and evidence-based efficacy of meditation and mindfulness-based interventions, there is still a lack of data about the possible unwanted effects (UEs) of these practices. The aim of this study was to evaluate the occurrence of UEs among meditation practitioners, considering moderating factors such as the type, frequency, and lifetime duration of the meditation practices. METHODS: An online survey was developed and disseminated through several websites, such as Spanish-, English- and Portuguese-language scientific research portals related to mindfulness and meditation. After excluding people who did not answer the survey correctly or completely and those who had less than two months of meditation experience, a total of 342 people participated in the study. However, only 87 reported information about UEs. RESULTS: The majority of the practitioners were women from Spain who were married and had a University education level. Practices were more frequently informal, performed on a daily basis, and followed by focused attention (FA). Among the participants, 25.4% reported UEs, showing that severity varies considerably. The information requested indicated that most of the UEs were transitory and did not lead to discontinuing meditation practice or the need for medical assistance. They were more frequently reported in relation to individual practice, during focused attention meditation, and when practising for more than 20 minutes and alone. The practice of body awareness was associated with UEs to a lesser extent, whereas focused attention was associated more with UEs. CONCLUSIONS: This is the first large-scale, multi-cultural study on the UEs of meditation. Despite its limitations, this study suggests that UEs are prevalent and transitory and should be further studied. We recommend the use of standardized questionnaires to assess the UEs of meditation practices.