Introduction
Mindfulness is well-known to have positive effects on mental health. In clinical trials, Mindfulness Based Stress Reduction (MBSR) and other mindfulness-based interventions showed positive effects on mental health among clinical populations (e.g., Bohlmeijer et al.
2010; Grossman et al.
2004; Khoury et al.
2013). Positive effects of mindfulness on mental health have further been observed among experienced meditators (for a review, see Hölzel et al.
2011; for primary data, see, for example, Baer et al.
2008 or Tran et al.
2014), and for mindfulness-based trainings and interventions in community samples (Agee et al.
2009; Szekeres and Wertheim
2015), in an educative context (Langer et al.
2015), and in a workplace context (Ravalier et al.
2016).
Consequently, research increasingly focuses on the mechanisms of mindfulness. Current research suggests that improvements in attention regulation, body awareness, and emotion regulation, and a less static perspective about the self (Hölzel et al.
2011) may be responsible for the positive effects of mindfulness on mental health. This model has been further cast into a neurobiological framework, for which there is ample support from neuroscience studies of meditation practice and among experienced meditators (Vago and Silbersweig
2012). Clinical research has yielded empirical evidence of related postulated mechanisms of mindfulness-based cognitive therapy; however, more data and evidence of causal specificity of these mechanisms still are needed (Van der Velden and Roepstorff
2015).
Mindfulness may be considered as a skill which can be increased by training (Bishop et al.
2004), while it also is a dispositional trait which may be assumed to be present in every person (Brown and Ryan
2003). Individuals are dispositionally more or less mindful, even in the absence of any training, be it formal or informal. These current views of mindfulness as being both a skill and a trait may strike as inconsistent or conflicting, but, empirically, they rather complement each other. Widely used instruments for the assessment of trait mindfulness, like the Five Facet Mindfulness Questionnaire (FFMQ; Baer et al.
2006), are highly sensitive to change (e.g., Bohlmeijer et al.
2011) and are routinely used in intervention studies. Mindfulness-based interventions were found to increase trait mindfulness, and these increases also explain treatment effects on mental health (for meta-analytic evidence and reviews, see Gu et al.
2015; Van der Velden and Roepstorff
2015). Similarly, meditation training is linked with higher trait mindfulness, as measured with the FFMQ (e.g., Baer et al.
2008; Taylor and Millear
2016; Tran et al.
2014). For a recent attempt to disentangle the trait and state components of one specific scale that intends to measure state mindfulness, see Medvedev et al. (
2017).
Drawing on the theoretical framework of potential mechanisms of mindfulness, as proposed by Hölzel et al. (
2011), research among experienced meditators (Tran et al.
2014) has shown that meditation experience and mindfulness are positively associated with indicators of all proposed mechanisms, i.e., attention regulation, body awareness, emotion regulation, and a change in perspective on the self. However, only improvements in emotion regulation and body awareness, but not in attention regulation, and a less static perspective about the self (nonattachment; see below) explained the effects of trait mindfulness on mental health. Body awareness appeared to be a specific pathway for the effects of trait mindfulness on symptoms of anxiety, whereas nonattachment (i.e., the relative absence of a fixation on ideas, images, or sensory objects, and of internal pressure to get, hold, avoid, or change circumstances or experiences; Sahdra et al.
2010) for symptoms of depression.
In the light of an apparent malleability of trait mindfulness through mindfulness interventions and training, cross-sectional investigations into the potential mechanisms (i.e., mediators) of the associations between trait mindfulness and mental health in nonmeditating samples also appear to be useful, besides longitudinal and prospective research. Trait mindfulness shows associations with mental health not only among meditators, but also among the meditation-naïve. This begs the question which mechanisms explain these associations among the latter: are they the same as among experienced meditators or do they differ? Cross-sectional studies in nonmeditating samples could thus provide information on (1) candidate mechanisms that show promise for further study in longitudinal and intervention studies, because any mechanism that is causally linked with an outcome should also co-vary with this outcome (Kraemer et al.
2002; see also Kraemer et al.
1997); (2) mechanisms that are specific to mindfulness-based trainings and interventions. While cross-sectional mediation analysis cannot provide direct evidence on the causal specificity of candidate mechanisms (because it lacks the necessary temporal dimension), it may provide indirect evidence on whether mechanisms reported for interventions or training might be specific to them or not so, i.e., when mechanisms are not similarly observed to mediate the associations between the “naturally” occurring levels of trait mindfulness and mental health among meditation-naïve individuals. Insight into these issues may help in explaining the associations between trait mindfulness and mental health and may help clarifying the specific mechanisms of mindfulness-based interventions and meditation. It may also promote the development of effective therapies by uncovering mechanisms which might not be specific, but the importance of which may have been underestimated previously.
Meditators and nonmeditators not only differ in the level, but also in the structure of trait mindfulness: The five facets of the FFMQ (Observe, Describe, Acting with Awareness [Actaware], Nonjudging of Inner Experience [Nonjudge], Nonreactivity to Inner Experience [Nonreact]) fit onto a single higher-order factor of mindfulness only among experienced meditators (Baer et al.
2006,
2008). Among nonmeditating samples, Observe does not load on higher-order mindfulness and thus is seemingly not part of a common underlying construct (Baer et al.
2006). Tran et al. (
2013,
2014) proposed to explain these structural differences by applying an alternative two-factor higher-order structure to the FFMQ, which factors represent the two quintessential components of mindfulness brought forth by Bishop et al. (
2004): Orientation to experience (OTE; being open and curious about the world and accepting experiences without judgment) and self-regulated attention (SRA; the mental ability to concentrate attention on the present moment and to deliberately switch the object of attention). These two higher-order factors provide not only direct empirical support for a widely used theoretical model of mindfulness. They also allow for a parsimonious examination of the associations of the multi-facetted construct of mindfulness with other constructs, as the two higher-order factors of the FFMQ subsume all of its five lower-order factors. Observe and, among meditators, Nonreact and Describe were found to be specifically indicative of SRA, whereas Actaware and Nonjudge of OTE (Tran et al.
2013,
2014). Structural differences between meditators and nonmeditators in the single-factor model were quantified by the strength of association between SRA and OTE in the two-factor model. This association was modest among nonmeditators (
r = .20), whereas substantial among meditators (
r = .62–.69). Providing further support for the special link between meditation experience and Observe, Taylor and Millear (
2016) reported that increases of trait mindfulness apparently level off with more meditation experience, whereas remain stable for Observe.
Changes in the structure of trait mindfulness are further accompanied by changes in the associations of Observe with relevant outcomes. Previous research showed that Observe correlates slightly positively with symptoms of depression and anxiety in nonmeditating samples (e.g., Baer et al.
2006; Tran et al.
2013), possibly reflecting ruminative tendencies (i.e., repetitive thinking about negative outcomes). Only among meditators, all five facets of the FFMQ were consistently negatively associated with psychological symptoms (Baer et al.
2006,
2008; Tran et al.
2014).
It thus appears that there are marked differences between meditators and nonmeditators in trait mindfulness and its associations with mental health. It therefore seems possible that other mechanisms account for the associations of trait mindfulness with mental health among nonmeditators, as compared to meditators. Disentangling the mechanisms of mindfulness that are specific to meditation and intervention from mechanisms that provide common links between trait mindfulness and mental health in the absence of meditation training could help to elucidate the associations between trait mindfulness and mental health, and the effects of mindfulness-based interventions. Previous research suggests that in the general population emotion regulation largely mediates the associations between trait mindfulness and mental health (Freudenthaler et al.
2017); nonattachment mediates the associations between trait mindfulness and satisfaction with life, and life effectiveness (Sahdra et al.
2016). However, there are no studies which would have examined a wider range of candidate mechanisms simultaneously. As well, associations with emotion regulation have been investigated on the aggregate level (i.e., overall emotion regulation), rather than on the subscale level (e.g., impulse control or emotional awareness). This leaves open the question which of the individual aspects of emotion regulation might be the most important ones.
Mindfulness-based trainings and meditation (e.g., yoga) gained popularity in recent years and are also frequently sought after in the general population. Thus, the general population cannot be assumed to be fully meditation-naïve. Hence, meditation experience needs to be assessed and statistically controlled for in studies with general population samples. Further, previous studies by Tran et al. (
2014) and Freudenthaler et al. (
2017) investigated the associations of trait mindfulness with symptoms of depression and anxiety. Somatic complaints are widely prevalent in the general population as well (e.g., Kroenke
2003); hence, they are an additional outcome of interest.
The current study sought to test and to explore whether the associations between trait mindfulness and mental health are mediated by the same mechanisms among mostly meditation-naïve individuals of the general population as among experienced meditators (Tran et al.
2014). This was our Research Goal 1. Thus, we sought to test the replicability of findings that have previously been reported for meditators with a general population sample. We extend previous evidence (Freudenthaler et al.
2017; Sahdra et al.
2016; Tran et al.
2014) by including somatization symptoms and test the associations of the higher-order factors of mindfulness with a wider array of candidate mechanisms on their subscale level. Meditation experience was controlled for in the analysis. Further, previous studies with meditating and nonmeditating samples (Tran et al.
2013,
2014) proposed short forms of the FFMQ, showing that these had improved measurement properties, and fitted a two-factor higher-order model on the data. Consequently, the current study also utilized a short form of the FFMQ for analysis. Investigating the factorial validity of this short form, and whether the two-factor higher-order model replicably fitted well on new and independent data, was our Research Goal 2. We expected that a good factorial validity of the FFMQ short form and that a two-factor higher-order model of trait mindfulness would fit well to the general population data of the current study. In the absence of prior data suggesting otherwise, we hypothesized that mechanisms of mindfulness, and directions of effects, would broadly stay the same, but that effects would be smaller than in meditating samples (see Tran et al.
2014). Specifically, we expected that the associations of SRA with mental health would be smaller in the current general population sample, and, hence, that intervening mechanisms would explain comparably less variance.
Discussion
This study found that a mediational model, as previously obtained for experienced meditators (Tran et al.
2014), is equally applicable to the general population to explain the associations between trait mindfulness and mental health (Research Goal 1). However, exploratory analyses also suggested differences in the structure of this model which highlight differential associations of self-regulated attention with the mediating variables and mental health between experienced meditators and the general population. Replicating previous studies (Tran et al.
2013,
2014), we further obtained evidence of good factorial validity of a short form of the FFMQ and of a two-factor higher-order structure of this measure (Research Goal 2).
The results of the current study suggest—with regard to the investigated set of candidate mechanisms—that no differences exist between meditators and the general population in the variables and mechanisms that mediate the associations between mindfulness and mental health cross-sectionally. From all proposed mechanisms of action (Hölzel et al.
2011), emotion regulation appeared to be the most important, corroborating previous results (Freudenthaler et al.
2017; Tran et al.
2014). Extending previous results, we obtained evidence that impulse control and access to emotion regulation strategies might be differentially associated with symptoms of depression, and symptoms of anxiety and somatization. Assessing these two aspects of emotion regulation with a common scale, previous research among meditators was not able to detect this difference.
Acceptance of emotions was the only aspect of emotion regulation that had paths to all three investigated mental health outcomes. It thus appears to be of central importance for the links of mindfulness with mental health, which may also explain part of the apparent efficacy of acceptance and commitment therapy (ACT; Hayes et al.
1999) for a wide range of mental health problems (A-Tjak et al.
2015). Learning to accept, rather than control, painful feelings and sensations is one of the stated goals of ACT. Nonattachment was a major correlate of mindfulness in the current study and showed incremental validity in predicting symptoms of depression, corroborating previous findings among meditators (Tran et al.
2014). The observed similar association with anxiety appears to be a new finding in this context. Nonattachment bears resemblance to the concept and goals of cognitive defusion in ACT. Cognitive defusion aims at decreasing patients’ overidentification with their thoughts and treating them as fixed “truths.” It has been shown to contribute with a large effect size to the positive outcome of ACT (Levin et al.
2012). The authors of the NAS (the scale to measure this construct) built on a Buddhist background in constructing the scale. However, as can be derived from the results of the current study, but also from Sahdra et al. (
2016), nonattachment apparently does not depend on such a background. It seems to be a more general construct whose links with cognitive defusion need to be investigated in more detail in the future.
Taken together, the broad structural similarities of the mediational network of mindfulness and mental health of experienced meditators and the current general population sample suggest that mechanisms of mindfulness are not specific to meditation and training. Reconciling the current finding with previous results (Tran et al.
2014), meditation experience apparently modifies the strength and direction of associations of self-regulated attention with mediators and outcomes, but may not introduce new mechanisms of action. As expected, associations of self-regulated attention with mediating variables and mental health were mostly smaller in the current general population sample than among experienced meditators. Consequently, the amount of attributable variance was smaller as well (40 [this study] vs. 59% [Tran et al.
2014] for depression scores, 24 vs. 57% for anxiety scores). Also, the correlation between the higher-order factors of mindfulness was lower in the current general population sample than among experienced meditators, replicating previous findings in the general population (Tran et al.
2013). Thus, meditation experience apparently leads to a more homogeneous construct of psychometric mindfulness.
Future longitudinal and intervention studies should specifically target mechanisms pertaining to emotion regulation (see also Roemer et al.
2015), body awareness, and change of self (nonattachment) to investigate their probable causal role with regard to the effects of mindfulness on mental health. Previous longitudinal research showed that rumination mediates the effects of mindfulness on depressive symptoms (Petrocchi and Ottaviani
2016; Royuela-Colomer and Calvete
2016). Longitudinal studies on further aspects of emotion regulation, as suggested in the current study and elsewhere (e.g., Curtiss et al.
2017), and of nonattachment are needed. The observed specificity of impulse control and access to emotion regulation strategies for symptoms of anxiety, depression, and somatization also needs further study.
Body awareness was reported to mediate the effects of yoga practice on psychological well-being in a cross-sectional study (Tihanyi et al.
2016). Yet, as suggested by the current results, body awareness does not appear to be specific to the context of intervention and training. On the biological level, mindfulness training increases the activity of prefrontal regulatory regions which inhibit central stress processing regions (e.g., the amygdala), and reduces and modulates the reactivity of these regions (Creswell and Lindsay
2014; for meta-analytic evidence of the effects of mindfulness on physiological markers of stress, see Pascoe et al.
2017). Traditional Buddhist meditation typically starts with an initial training of attention regulation, often focusing on localized bodily sensations (e.g., respiration), before proceeding to a more general stage where awareness does not depend on the conscious selection and deselection of the attentional focus and which finally may result in psychological well-being (Hölzel et al.
2011; Lutz et al.
2008). The current data suggest that a bodily focus might pose a privileged starting point for this process, as even among the mostly meditation-naïve individuals of the current study, a connection between bodily awareness with self-regulated attention and mental health (anxiety) was apparent. However, without monitoring and training, this pathway may contribute to heightened symptom levels, as also was apparent in the current data.
Summing up, we obtained evidence that the mediational network that links mindfulness with mental health in the general population is broadly similar to the mediational network among experienced meditators. Differences pertained to the strength and direction of associations of self-regulated attention with the other variables in this network. Emotion regulation, body awareness, and change of self (nonattachment) appeared to be the most important mechanisms of action through which mindfulness exerts its beneficial effects on mental health. These mechanisms should be specifically targeted in longitudinal and intervention studies to examine their probable causal role. The utilized short form of the FFMQ can be recommended for further research for its good factorial validity. Mindfulness was replicably shown to have a two-factor higher-order structure with this measure in the general population.
Limitations
The cross-sectional design of this study precludes any causal interpretation of the presented results. Longitudinal studies are needed to investigate the possible causal role of investigated mediators for the effects of mindfulness on mental health. We used the FFMQ as a measure of trait mindfulness, but did neither investigate, nor intended to do so, the probable state and trait components of this popular measure (cf. Medvedev et al.
2017). State and trait components of mindfulness may be differentially associated with the investigated mediators and mental health outcomes. Our operationalization of meditation experience encompassed different styles of meditation. We were interested in controlling for prior meditation experience, but not to account for possible differences between various meditation styles. These may well differ regarding the extent to which they contribute to mindfulness. We utilized a variable-oriented approach to analysis in the attempt to replicate in the general population results that have previously been reported among meditators with the same methods. Person-centered approaches (e.g., latent profile analysis; see Pearson et al.
2015; Sahdra et al.
2017) may provide further insight into differences between meditators and the general population, or even within the general population itself. Also, facet-level analyses might reveal differences not similarly observable on the level of the higher-order factors. Lastly, the reported results are based on self-reports throughout, and thus potentially are prone to common-method variance effects.