Mindfulness training has become an increasingly useful clinical intervention for promoting emotion regulation (Hayes and Feldman 2004; Linehan 1993). Mindfulness training has been incorporated into psychotherapies for a variety of psychiatric disorders, including major depression (Segal et al. 2002), generalized anxiety disorder (Kabat-Zinn et al. 1992; Roemer and Orsillo 2002), borderline personality disorder (Linehan 1993), eating disorders (Kristeller and Hallett 1999), post-traumatic stress disorder (Wolfsdorf and Zlotnick 2001), and substance abuse (Marlatt 1994). Kabat-Zinn’s (1982, 1990) mindfulness-based stress reduction (MBSR) program is now widely available in a variety of medical and mental health settings. This program has been applied to reduce distress in occupational (Davidson et al. 2003) and educational settings (Rosenzweig et al. 2003) and in chronic pain (Kabat-Zinn et al. 1985) and oncology (Carlson et al. 2004) treatment settings. Two recent meta-analyses document the evidence for mindfulness training as an efficacious method of distress reduction in nonclinical populations, as well as in medical and psychiatric populations (Baer 2003; Grossman et al. 2004). There is even some evidence that mindfulness training is associated with decreases in alcohol, marijuana, and crack cocaine use in an incarcerated population (Bowen et al. 2006).

Mindfulness practice has a rich historical tradition as a way to develop emotional stability. Mindfulness training is a meditation technique that has been practiced by Buddhist monastic orders and laity for nearly 2,500 years. It was introduced within the Pali Canon of Buddhist scriptures in the Mahāsatipitṭ̣̣hāna Sutta (Walshe 1987) as a set of contemplative exercises to observe internal and external phenomena. Mindfulness meditation was venerated in the Buddhist tradition as a powerful and efficient technique to quiet the mind by active observation of the breath and various physical and psychological states (Gampopa 2000). In the context of Buddhist practice, this observation was intended to illustrate the impermanent nature of cognitive, affective, and physical phenomena. Recognizing these phenomena as impermanent, the practioner becomes less reactive and can maintain affective balance in the face of potentially difficult circumstances, a concept called equanimity. Mindfulness is still viewed in Buddhist traditions as a cornerstone for cultivating affective balance (Wallace and Shapiro 2006).

Mindfulness training teaches participants to cultivate a new relationship with internal experiences that involves regulating attention so that it is maintained on immediate experience, without avoiding, overengaging, or elaborating the experience. The practitioner also learns to approach experiences with an orientation of acceptance and observation, regardless of the valence and desirability of the experience (Bishop et al. 2004). Consistent with early Buddhist perspectives, mindfulness meditation in Western practice is hypothesized to develop a distance from, or “decentered” relationship with, one’s internal and external experiences, thereby decreasing emotional reactivity and facilitating a return to baseline after reaction (Segal et al. 2002; Teasdale 1999).

Several lines of research suggest that emotion regulation is an essential component of mental health and that problems of regulation are associated with a variety of forms of psychopathology (Cicchetti et al. 1995; Davison 2000; Gross 1998). In traditional Buddhist writings, mindfulness is thought to improve well-being by reducing tendencies towards aversion and attachment to internal and external phenomena, which facilitates emotional regulation (Kumar 2002; Wallace and Shapiro 2006). In contrast, less adaptive approaches to internal experience have been characterized as under- or over-engagement with internal experiences (Buchheld et al. 2002; Hayes and Feldman 2004; Kabat-Zinn 1990). The concepts of aversion and under-engagement are consistent with the widely-studied concept of experiential avoidance, a maladaptive form of emotion regulation characterized by avoidance of disturbing emotions, thoughts, images, memories, and physical sensations (Hayes et al. 1996). The concepts of attachment and over-engagement are consistent with the concept of depressive rumination, which involves thoughts and behaviors that repetitively and passively focus one’s attention on one’s negative mood, circumstances, and personal shortcomings (Nolen-Hoeksema 1991). There is substantial evidence that both avoidance and overengagement with emotions are associated with worse psychological and physical health outcomes (Gross 2002; Keicolt-Glaser et al. 2002; Salovey et al. 2000; Segerstrom et al. 2003). Consistent with the original instruction of mindfulness in the Mahāsatipitṭ̣̣hāna Sutta, Kabat-Zinn (2003) contrasts mindfully allowing oneself to acknowledge and experience emotional pain with emotional avoidance, suppression, and preoccupation.

The problems of avoidance and overengagement are central to the maintenance of depression. Thought suppression (Beevers et al. 1999; Wenzlaff and Luxton 2003) and avoidant coping and problem solving (Ottenbreit and Dobson 2004) are attempts to regulate negative thoughts and emotions, but these strategies often exacerbate problems and contribute to depression. Wenzlaff and Luxton (2003) demonstrated that efforts to avoid unpleasant thoughts in the face of stressors led to a rebound of these thoughts and to more subsequent rumination and dysphoria. Rumination also maintains periods of dysphoric mood (Nolen-Hoeksema et al. 1993) and predicts the onset of symptoms of depression and anxiety (Nolen-Hoeksema 2000). Training in mindfulness offers an alternative response that can interrupt destructive cycles of avoidance and overengagement (Segal et al. 2002; Teasdale 1999; Teasdale et al. 2000). For instance, recent studies have found that MBSR reduces depressive rumination (Ramel et al. 2004) and that participants instructed to apply mindfulness meditation are more effective at decreasing an experimentally-induced negative mood than those instructed to ruminate or distract (Broderick 2005). Similarly, Arch and Craske (2006) demonstrated in a nonclinical sample that a mindfulness focused-breathing induction produced less avoidance of aversive stimuli than an unfocused attention induction.

Evidence is accumulating to suggest that mindfulness training is associated with improvement on a variety of indicators of mental and physical functioning, but few researchers have assessed whether mindfulness indeed changes after training. This is in part because until recently, there were few available measures of mindfulness (Baer 2003). The few studies that have been conducted on change in mindfulness have yielded mixed results. In a nonclinical sample of experienced meditators, participants attending Vipassana meditation retreats reported statistically significant gains on the Freiburg Mindfulness Inventory (Buchheld et al. 2002; Walach et al. 2006). Self-reported mindfulness scores, as measured by the Toronto Mindfulness Scale (TMS, Lau et al. 2006), also increased in a mixed sample of psychiatric and medical patients after an 8-week MBSR group intervention. In contrast, a sample of cancer patients in a mindfulness-based stress reduction course did not report significant increases in mindfulness on the Mindful Awareness Attention Scale (MAAS, Brown and Ryan 2003). However, increases in mindfulness over the course of the intervention were associated with declines in mood disturbance and stress (Brown and Ryan 2003).

In the present study, we examined whether mindfulness increased significantly in an open trial of an exposure-based cognitive therapy for depression (EBCT: Hayes et al. 2005; Hayes et al. 2007) that includes a component of mindfulness training. Mindfulness was measured with the Cognitive and Affective Mindfulness Scale, a new scale that we developed to assess four aspects of mindfulness: (1) the ability to regulate attention, (2) an orientation to present or immediate experience, (3) awareness of experience, and (4) an attitude of acceptance or nonjudgment towards experience. The mindfulness component of the therapy is designed to teach attentional control and distress tolerance and to reduce avoidance and rumination as primary emotion regulation strategies. Mindfulness training helps provide emotional stability and prepares clients for the next more disturbing phase of therapy, which involves emotional processing of depressive material and movement toward new meanings (Hayes and Feldman 2004). We predicted that mindfulness would increase significantly from pretreatment to posttreatment, that changes in mindfulness would be associated with decreases in avoidance and rumination, and that changes in mindfulness would be associated with the course of recovery from depression.

Method

Data for the present study are drawn from an open trial of an exposure-based cognitive therapy for depression developed by the third author. The methodology and outcome of this trial have been presented in detail elsewhere (Hayes et al. 2005; Hayes et al. 2007). Key details are presented below to provide context for the present analyses.

Participants

All participants sought treatment for depression in a university-based clinic, and those who met criteria for Major Depressive Disorder, using the Structured Clinical Interview for DSM-IV (SCID; First et al. 1995), were included in the study. Those who met criteria for bipolar disorder, psychotic disorder, borderline personality disorder, current substance abuse, or current suicidality were not included in the study but were referred back to the general clinic for treatment.

The sample was 66% female and 34% male and was also ethnically diverse in that 51% were Hispanic/Latino, 39% White, 2% Asian-American, 2% African-American, and 6% were of Other or Mixed heritage. The mean age was 36.76 (range 16–58). Most participants had some college education (89%) and were not married or cohabiting (73%). The median number of previous depressive episodes was 2.5. Of the 33 participants who enrolled in therapy, 29 completed at least 12 of the 20 sessions of the program and were considered completers. Only four (12%) clients did not complete the therapy, and all of those discontinued before session eight. Of the four who did not complete therapy, two clients moved, one became pregnant and had difficulty attending therapy sessions, and one discontinued for unknown reasons.

Exposure-Based Cognitive Therapy for Depression (EBCT)

This therapy consists of 20–24 sessions over the course of three phases. The skills taught are designed to be used as part of a healthy lifestyle beyond the depressive episode. Mindfulness meditation training is one component of this integrative therapy. Therapists (18 masters-level student therapists and 2 Ph.D.-level therapists) received weekly individual and biweekly group supervision and were trained in basic mindfulness meditation practice by the first author, who has extensive experience with the practice.

The first phase of therapy (sessions 1–8) focuses on stress management. This part of the therapy is designed to restore depleted energy, coping resources, and social support, and to increase the motivation for change. Clients are taught problem-solving and coping skills, healthy lifestyle skills (e.g., healthy eating, sleep, and exercise habits), and mindfulness meditation. Participants are also taught about healthy relationships and attachment patterns, and exercises are aimed at reducing interpersonal stressors and increasing social support. This first phase of therapy teaches healthy habits that take a while to incorporate into one’s life, so they are introduced early and addressed throughout the course of therapy.

We have adapted principles and techniques from traditional Buddhist meditation exercises, Jon Kabat-Zinn’s stress management approach (1990), and from Segal et al.’s (2002) mindfulness-based relapse prevention approach. A module was constructed by the first author to outline the basic practice for therapists and clients. The module was designed as an instructive and also interactive presentation on mindfulness meditation. The practice focuses on diaphragmatic breathing and teaching the principles of bare attention, present-focus, and acceptance/nonjudgment, as they relate to internal experiences. Clients are taught the concept of mindful engagement with emotions, and they learn to notice instances of avoidance and overengagement with emotions, as well as the consequences of these strategies in their own lives. Meditation is difficult to do in this early phase, so we introduce the training in session four and in a graded way such that people meditate a little each day and increase their endurance. In addition, clients write essays each week about their depression throughout the course of therapy. Both the meditation and writing exercises are conceptualized as gradual forms of exposure to disturbing emotions (Hayes and Feldman 2004).

The stress reduction phase is thought to help prepare clients for the second phase of therapy (sessions 9–18), which is destabilizing. In this phase, clients use the skills that they have learned to approach the material that they had alternately avoided and become overwhelmed by in the process of rumination. The disturbing material most often involves negative views of the self and a sense of hopelessness and dread. We conceptualize this as the activation/exposure phase of therapy in that it involves directly accessing and exploring negative experiences mindfully, without avoiding and ruminating. A transient period of symptom exacerbation occurs, and then the previously disturbing material becomes less feared and overwhelming, allowing for cognitive and emotional processing to occur, and facilitating movement to active problem solving and development of a more balanced view of self and one’s future (Hayes et al. 2005, 2007).

The principles of this therapy build on Segal et al.’s (2002) mindfulness-based cognitive therapy for relapse prevention, but our therapy places more emphasis on destabilizing and changing depressive patterns in the acute phase of depression. The strategies used also combine elements of Greenberg’s (2002) experiential therapy for depression, schema-focused therapies (Beck et al. 2004; Young et al. 2003), and exposure and cognitive/emotional processing principles from therapies for post-traumatic stress disorder (Cohen et al. 2006; Foa and Rothbaum 1997; Resick and Schnicke 1993).

The third phase of the therapy (sessions 19–20 to 24) is the consolidation and positive growth phase. In this phase, we help clients to look to the future and set realistic goals for the upcoming months. We have them actively work on developing a more healthy view of the self, clarifying their sense of meaning and purpose, and applying mindfulness skills to positive emotions and experiences so that they are not avoided or suppressed. We highlight again the importance of the life skills that clients have learned to maintain emotional balance, and we review the relevant signs of relapse for that individual and relapse prevention strategies.

Symptoms of Depression and Emotion Regulation Strategies

Beck Depression Inventory-II (BDI-II; Beck et al. 1996)

The BDI-II is a widely-used self-report measure that assesses depression severity. The BDI-II consists of 21 items and measures the presence and severity of cognitive, motivational, affective, and somatic symptoms of depression. Internal reliability (α = .92) and test-retest reliability (r = .93) for the BDI is good in outpatient samples (Beck et al. 1996). The BDI has been found to be valid among psychiatric outpatient samples (Beck et al. 1996). In the present study, the BDI-II was administered weekly during the course of therapy. For these weekly assessments, clients were instructed to rate symptoms over the last week. Possible scores on the BDI-II range from 0 to 63.

Modified Hamilton Rating Scale for Depression (MHRSD; Miller et al. 1985)

The MHRSD is a 25-item, interview-based assessment of depression severity. The MHRSD contains 17 items that assess the same symptoms as the original Hamilton Rating Scale for Depression (HRSD; Hamilton 1960), and the MHRSD also has acceptable reliability and validity (Miller et al. 1985). Ratings for these items are summed and typically used to determine depression severity (i.e., 17-item MHRSD score). The MHRSD contains an additional 8 items that assess other aspects of depression. These additional items assess worthlessness, helplessness, hopelessness, quality of mood, mood reactivity, and diurnal variation in symptoms. The MHRSD has excellent inter-rater reliability, and the 17-item MHRSD correlates highly with the original Hamilton Rating Scale for Depression (Miller et al. 1985). We used the 17-item MHRSD to be consistent with other outcomes studies on the treatment of depression. Possible scores on the MHRSD range from 0 to 50.

The MHRSD was administered biweekly across the course of therapy. Because of the intensive assessment schedule, therapists administered the interview. An independent clinical assessor rated 20% of the sample of tapes for each client to assess inter-rater agreement on the MHRSD. Because total scores were used in all analyses, agreement was assessed on total scores. Agreement between raters was high (intra-class correlation = .92) (Table 1).

Table 1 Descriptive statistics for pre and posttreatment values of measures of depression symptoms and emotion regulation
Full size table

Mindfulness

The Cognitive and Affective Mindfulness Scale (CAMS) is an 18-item measure that was developed to assess mindfulness, which we defined as nonjudgmental, awareness of present experiences, emotions, and thoughts (Kumar 2005). The CAMS was administered at the beginning and end of therapy. The items on the CAMS were designed to assess four core characteristics of mindfulness described by Kabat-Zinn (1990): (1) the ability to regulate attention [“I have a hard time concentrating on what I am doing,” (reverse-scored)], (2) an orientation to present or immediate experience [e.g., “I focus on the present moment”, “I am preoccupied with the past” (reverse scored)], (3) awareness of experience (e.g., “It’s easy for me to keep track of my thoughts and feelings”), and (4) an attitude of acceptance or nonjudgment towards experience (e.g., “I believe it is OK to be sad or angry”). These four components were also emphasized by a recent consensus panel (Bishop et al. 2004) convened to provide a common operational definition for researchers.

Respondents are asked to rate how much each statement applies to them from 1 (rarely/not at all) to 4 (almost always). The internal consistency of the questionnaire in this sample (α = .64 at both pre and posttreatent) was acceptable for a questionnaire in development for use in research (Nunnally 1967). Items that reflect the absence of mindfulness are reverse scored and summed with items that reflect the direct assessment of mindful qualities. Possible scores on the CAMS range from 18 to 72, with higher total scores reflecting greater mindfulness. In a sample of undergraduate students (Feldman and Hayes 2005), the CAMS demonstrated levels of internal consistency (α = .65) comparable to the present study, as well as evidence of concurrent validity. The CAMS shared significant positive associations with measures of well-being and emotional intelligence and with two other self-report measures of mindfulness. The CAMS was also inversely associated with measures of anxiety, depression, experiential avoidance, thought suppression, rumination, and worry in that sample.

Subsequent to the initiation of the present study, the CAMS has been further refined in a series of psychometric studies, and the resulting measure was named the Cognitive and Affect Mindfulness Scale—Revised (CAMS-R; Feldman et al. 2007). The CAMS-R consists of 12 items and contains 6 items drawn from the original CAMS and 6 items that were added in subsequent revisions. In an undergraduate sample (Feldman and Hayes 2005), the CAMS and CAMS-R were strongly intercorrelated (r = .66). When we began this area of study, no self-report measures of mindfulness were available. In addition to the CAMS-R, there are now several other self-report measures of mindfulness (Baer et al. 2004; Brown and Ryan 2003; Buchheld et al. 2002; Lau et al. 2006), and the CAMS compares favorably to many of the strengths of these measures (Baer et al. 2006; Feldman et al. 2007).

Experiential Avoidance

The Acceptance and Action Questionnaire (AAQ; Hayes et al. 2004) is a measure of unhealthy efforts to escape or avoid emotions, thoughts, and memories; unhealthy efforts to control or suppress private experience; experiential acceptance; and taking action despite uncertainty and/or distress. The AAQ was administered at pretreatment and posttreatment. We used a preliminary 16-item version of the scale that was available when the present study began. The authors of this measure subsequently developed a 9-item version of the instrument. (Hayes et al. 2004). The authors indicate that the 16-item version has considerable item overlap with and performs “in a fashion that is virtually identical” (p. 562) to the 9-item version in their initial psychometric studies. The 9-item version has since been shown to have internal consistency, convergent, discriminant, concurrent, and incremental validity, and treatment utility (Hayes et al. 2004). The authors hypothesize that the 16-item version may be preferable in intervention research, as “the larger number of items may allow smaller changes throughout therapy to be detectable” (p. 563). Possible scores on the AAQ range from 16 to 112, with higher scores indicating more avoidance.

Rumination

Rumination was measured at pretreatment and posttreatment with the 22-item rumination subscale from the Response Style Questionnaire (Nolen-Hoeksema and Morrow 1991). Participants indicate on a four-point scale (1 = almost never, 4 = almost always) the extent to which, when feeling depressed, they focus on themselves, their symptoms, and the possible antecedents and consequences of their mood. Possible scores on the RSQ range from 22 to 88, with higher scores indicating more rumination. Previous studies have shown the scale to have acceptable convergent and predictive validity (Nolen-Hoeksema 2000).

Results

As reported previously (Hayes et al. 2005, 2007), growth-curve analyses revealed that there was a significant linear decrease in depression (self-report and interview) over the course of therapy in both the intent-to-treat and the completer samples. Paired sample t-tests also revealed significant pretreatment to posttreatment change in depression, and effect sizes were large. Those in the completer sample attended at least 12 sessions and received an adequate dose of the activation/exposure phase, which is central to exposure-based cognitive therapy. Therefore, as in other reports on this sample, the present study will focus on the completer sample.

We examined change in mindfulness, avoidance, and rumination from pretreatment to posttreatment, using paired samples t-tests. We then calculated pretreatment to posttreatment residualized gain scores on each of these measures and examined the correlations of change in mindfulness with change in avoidance and rumination, consistent with Brown and Ryan’s (2003) method of studying change in mindfulness.

We used the individual growth-curve modeling application of hierarchical linear modeling (HLM; Raudenbush and Bryk 2002) to examine the associations between change in mindfulness, as assessed by the CAMS, and the trajectory of change in depression on the BDI and MHRSD over the course of therapy. HLM is increasingly being used to analyze repeated-measures data from intervention studies because it allows for use of all available data and is robust to missing data, and this approach allows for examination of predictors of symptom change across multiple assessments (Gueorguieva and Krystal 2004). In the present analyses, the rate of change in depression was calculated as a Level 1 equation (within-subjects), and residualized gain scores of mindfulness were a Level 2 (between-subjects) predictor of the rate of change in depression. These results indicate whether individuals who reported greater increases in mindfulness during treatment also reported greater decreases in depression symptoms across the course of therapy. Growth-curve analyses were performed using HLM 6 software (Raudenbush et al. 2004).

Although EBCT includes only a component of mindfulness training as part of a larger package of interventions, paired sample t-tests revealed that mindfulness did increase significantly from the beginning to end of therapy (t = 5.35; p < .001, d = .75). As predicted, the maladaptive emotion regulation strategies of avoidance (t = −5.47, p < .001, d = .61) and rumination (t = −4.54, p < .001, d = .88) decreased significantly over this time period. In addition, correlations between the amount of change (residualized gain scores) in mindfulness and these two emotion regulation strategies revealed that more improvement in mindfulness was significantly correlated with concurrent decreases in avoidance (r = −.38, p = .045) and rumination (r = −.48, p = .009).

We next examined whether change in mindfulness (residualized gain score of pretreatment to posttreatment change) was associated with the week-to-week trajectories of depression scores on self-report and interview measures (HLM). Growth-curve analyses revealed that increase in mindfulness over the course of therapy was a significant Level I predictor of a linear decrease over time in depression symptoms on both the BDI (Coefficient = −10.32, SE = 3.62, t = −2.85, p = .01) and on the MHRSD (Coefficient = −3.53, SE = 1.40, t = −2.50, p = .02).

Discussion

Self reported mindfulness increased significantly over the course of an integrative, exposure-based cognitive therapy for depression that includes training in mindfulness meditation. The change in mindfulness was associated with reductions in experiential avoidance and rumination, as well as with a decrease in depression symptoms over time on both self-report and clinician-administered interview. As proposed in theoretical writings on the application of mindfulness to emotion regulation (Buchheld et al. 2002; Hayes and Feldman 2004; Kabat-Zinn 1990; Segal et al. 2002; Teasdale 1999), increases in mindfulness appear to go hand-in-hand with reductions in avoidance and overengagement with upsetting emotions and thoughts.

This is a preliminary study in which mindfulness is one component of a multi-component therapy for depression. The mindfulness training that we taught did not include the full package of Kabat-Zinn’s MBSR (1982, 1990) program or Segal et al.’s MBCT (2002) relapse prevention program. For example, exercises related to yoga and the body scan were not included. The primary focus of these programs is on mindfulness training, whereas our therapy includes multiple components designed to reduce depression in the acute episode and also to prevent relapse. As in other integrative treatments designed for the acute phase of treatment, mindfulness is one component of many (Hayes et al. 1999; Linehan 1993; Marlatt 1994). Interestingly, the MBCT approach is presented to clients after they have recovered from depression, and it has been shown to significantly reduce relapse, but only in those who have experienced three or more previous episodes of depression (Teasdale et al. 2000; Ma et al. 2004). Our research suggests that individuals with depression might also benefit from mindfulness training in the acute phase of treatment, but in the context of other stress management skills and interventions aimed at schema and behavior change (Hayes and Feldman 2004).

The change in self-reported mindfulness following this integrative therapy for depression is consistent with other studies showing that mindfulness improves with training (Buchheld et al. 2002; Lau et al. 2006; Walach et al. 2006) and that change in mindfulness is associated with distress reduction (Brown and Ryan 2003). The present study extends these findings by suggesting that change in mindfulness is associated with reduction in depression symptoms and maladaptive emotion regulation strategies. However, it is not yet clear whether the increases in self-reported mindfulness are due specifically to the mindfulness training. It is also possible that other emotion regulation interventions in the stress management phase contributed to the changes in mindfulness. In addition, because this was an open trial of a new therapy, there was no control or comparison condition, so we could not assess change in mindfulness over time in the absence of training.

The question of specificity in mindfulness interventions deserves further study across interventions. Some have noted that even “pure” mindfulness training interventions, such as MBSR, also contain cognitive, behavioral, and psychoeducational interventions (Dimidjian and Linehan 2003; Roemer and Orsillo 2003). Given the centrality of mindfulness in psychological well-being (Brown and Ryan 2003; Wallace and Shapiro 2006), it is important to determine if mindfulness can be cultivated only through mindfulness training, or whether individuals can also learn to respond in mindful ways to their emotions with other forms of psychotherapy (see Horowitz 2002; Martin 1997). For instance, experiential therapy is designed to help clients experience emotions more fully and to engage with emotions in a way that is very consistent with mindfulness training—attention to and awareness of emotions, a present-centered focus, and a nonjudgmental stance (Greenberg 2002). A number of behavioral and cognitive-behavioral authors have likened mindfulness practice to interoceptive exposure (e.g., Baer 2003; Hayes and Feldman 2004; Linehan 1993; Roemer and Orsillo 2002) in that clients are encouraged to confront disturbing emotions and allow the intensity of the experience to diminish through habituation rather than unhealthy avoidance strategies. Empirical evidence also suggests that increases in metacognitive awareness (a “decentered” perspective), one proposed mechanism of mindfulness interventions, occurs in both MBCT and in cognitive therapy for depression and is associated with symptom reduction in both treatments (Teasdale et al. 2002). The specificity of mindfulness training could be addressed, as suggested by Roemer and Orsillo (2003), in the context of either a dismantling study of MBSR or through randomized contol trials comparing mindfulness training to emotion-focused therapy or exposure-based interventions.

Change in mindfulness was associated with concurrent changes in self reports of avoidance and rumination. These findings are consistent with suggestions that mindfulness offers an alternative response that can interrupt destructive cycles of avoidance and overengagement (Segal et al. 2002; Teasdale 1999; Teasdale et al. 2000) and that MBSR can reduce depressive rumination (Ramel et al. 2004). Our findings also complement those from another study from our treatment development work. In that study, we had raters code the content of the weekly essays that clients wrote about their depression. Clients with higher levels of avoidance in their essays during the activation/exposure phase of therapy reported less improvement on both measures of depression (BDI, MHRSD) over the course of therapy (Hayes et al. 2005). More avoidance was also associated with less cognitive/emotional processing in the essays, which is the goal of the activation/exposure phase of therapy and was an important predictor of improvement in depression. As we have suggested elsewhere, mindfulness might not only help to reduce avoidance and rumination, but it might also provide clients with a foundation for the more destabilizing aspects of therapy, such as cognitive/emotional processing (Hayes and Feldman 2004).

A strength of the present study is the use of a sample of clinically-diagnosed individuals receiving treatment for Major Depressive Disorder (MDD). The present results contribute to a growing body of literature suggesting that mindfulness may be a valuable component in the treatment of depression (Segal et al. 2002). The use of a clinical sample in this study also extends the empirical literature on the emotion regulation correlates of self-reported mindfulness, as most published studies have focused on undergraduate and community samples (Baer et al. 2006; Brown and Ryan 2003; Feldman et al., in press). In addition, research on whether self-reported mindfulness can change has focused on nonclinical samples of experienced meditators (Buchheld et al. 2002; Walach et al. 2006), medical patients (Brown and Ryan 2003), and heterogeneous samples of patients with medical and psychiatric disorders (Lau et al. 2006) rather than on clinical depression. In addition, the culturally-diverse sample in our study extends the generalizability of past findings on correlates of mindfulness and its degree of change.

An important limitation of the present study is that the design does not make clear the temporal sequencing of the changes in mindfulness, avoidance, rumination, and depression. Mindfulness, rumination, and avoidance were assessed only at pretreatment and posttreatment, thus precluding mediational analyses (Kraemer et al. 2001). If mindfulness is hypothesized to be a mechanism by which avoidance and rumination decrease, future studies will need to include more frequent assessments of mindfulness over the course of therapy and also include a control condition and random assignment. Our correlational analyses provide an initial glimpe at the general associations between mindfulness, emotion regulation, and depression, and the findings suggest that more sophisticated analyses of the role of mindfulness in the change process might be warranted.

A second limitation of the present study is that two of the constructs (mindfulness and experiential avoidance) were assessed with preliminary versions of questionnaires that were subsequently revised before publication (CAMS and AAQ, respectively). As noted previously, when the present study was undertaken, measures of experiential avoidance and mindfulness had not been published. However, the preliminary versions of the CAMS and AAQ share comparable psychometric properties with the versions of the measures that were subsequently published.

Despite these limitations, the present study suggests that mindfulness training, which has been widely demonstrated to reduce distress and symptoms of psychopathology (Baer 2003; Bishop et al. 2004), may also increase mindfulness, which is more than the reduction of distress. These results also suggest that increases in mindfulness were associated with more change in depression symptoms, experiential avoidance, and rumination. These findings represent an exciting convergence of descriptions of mindfulness in ancient Buddhist texts and contemporary studies of psychopathology, emotion regulation, and clinical interventions. Recent developments in operationalizing (Bishop et al. 2004) and measuring mindfulness (Baer et al. 2004; Brown and Ryan 2003; Buchheld et al. 2002; Feldman et al. 2007; Lau et al. 2006) have opened the possibility of studying how cognitions and emotion regulation strategies change with mindfulness training and perhaps to understand the process by which these ancient meditation practices might have their effects.