Mindfulness Training in a Heterogeneous Psychiatric Sample: Outcome Evaluation and Comparison of Different Diagnostic Groups

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1 Mindfulness Training in a Heterogeneous Psychiatric Sample: Outcome Evaluation and Comparison of Different Diagnostic Groups Elisabeth H. Bos, 1,2 Ria Merea, 1 Erik van den Brink, 1 Robbert Sanderman, 3 and Agna A. Bartels-Velthuis 1,2 1 Lentis Mental Health Organization, Center for Integrative Psychiatry, Groningen, the Netherlands 2 University of Groningen, University Medical Center Groningen, University Center for Psychiatry, Groningen, the Netherlands 3 University of Groningen, University Medical Center Groningen, Health Psychology Section, Groningen, the Netherlands Objectives: To examine outcome after mindfulness training in a heterogeneous psychiatric outpatient population and to compare outcome in different diagnostic groups. Method: One hundred and forty-three patients in 5 diagnostic categories completed questionnaires about psychological symptoms, quality of life, and mindfulness skills prior to and immediately after treatment. Results: The mixed patient group as a whole improved significantly on all outcome measures. Differential improvement was found for different diagnostic categories with respect to psychological symptoms and quality of life: Bipolar patients did not improve significantly on these measures. This finding could be explained by longer illness duration and lower baseline severity in the bipolar category. Conclusion: Mindfulness training is associated with overall improvement in a heterogeneous outpatient population. Differences in outcome between diagnostic categories may be ascribed to differences in illness duration and baseline severity. C 2013 Wiley Periodicals, Inc. J. Clin. Psychol. 00:1 12, Keywords: mindfulness training; depressive disorder; anxiety disorder; adjustment disorder; bipolar disorder Mindfulness refers to the awareness that emerges through paying attention on purpose, in the present moment, and nonjudgmentally to the unfolding of experience moment by moment (Kabat-Zinn, 2003, p. 145). The practice of mindfulness includes observing and attending to internal and external experiences as they occur in the here and now and cultivating a nonevaluative and open attitude to these experiences (Kabat-Zinn, 1982, 1990; Bishop et al., 2004). Increased mindfulness is thought to improve psychological functioning, presumably by promoting an adaptive form of self-focused attention that reduces rumination and emotional avoidance and improves behavioral self-regulation (Baer, 2009; Kuyken et al., 2010). Jon Kabat-Zinn developed the mindfulness-based stress reduction (MBSR) training in the 1970s to help patients suffering from chronic pain and stress cope with their complaints (Kabat- Zinn, 1990). About two decades later, mindfulness-based cognitive therapy (MBCT) was developed by Teasdale and colleagues, combining elements of MBSR and cognitive therapy, aimed at preventing recurrence in depressive disorder (Teasdale, Segal, & Williams, 1994; Teasdale et al., 2000). Several randomized controlled studies conducted since then have shown that MBSR is indeed effective in improving mental health in clinical as well as nonclinical populations (Grossman, Niemann, Schmidt, & Walach, 2004; Hofmann, Sawyer, Witt, & Oh, 2010; Fjorback, Arendt, Ornbol, Fink, & Walach, 2011), while MBCT was found to be effective in preventing recurrence in remitted depressed patients (Piet & Hougaard, 2011; Chiesa & Serretti, 2011; Van Aalderen et al., 2012). Please address correspondence to: Dr. Bos, Elisabeth, P.O. Box , Groningen 9700RB. [email protected], [email protected] JOURNAL OF CLINICAL PSYCHOLOGY, Vol. 00(0), 1 12 (2013) Published online in Wiley Online Library (wileyonlinelibrary.com/journal/jclp). C 2013 Wiley Periodicals, Inc. DOI: /jclp.22008

2 2 Journal of Clinical Psychology, xxxx 2013 Both in somatic medicine and psychiatry, mindfulness training (MBSR/MBCT) is being used more and more in a wide range of diagnostic categories. A number of studies suggest that mindfulness training may also have beneficial effects in currently symptomatic depression (Chiesa & Serretti, 2011), eating disorder (Wanden-Berghe, Sanz-Valero, & Wanden-Berghe, 2011), sleeping disorder (Winbush, Gross, & Kreitzer, 2007), and psychosis (Langer, Cangas, Salcedo, & Fuentes, 2012). Furthermore, some preliminary evidence has been found for positive effects in bipolar disorder (Deckersbach et al., 2012; Stange et al., 2011; Williams et al., 2008), generalized anxiety disorder (Hofmann et al., 2010; Kim et al., 2010a), panic disorder (Kim et al., 2010b), social phobia (Piet, Hougaard, Hecksher, & Rosenberg, 2010), hypochondriasis (Lovas & Barsky, 2010; Williams, McManus, Muse, & Williams, 2011; McManus, Surawy, Muse, Vazquez-Montes, & Williams, 2012), and substance use disorder (Zgierska et al., 2009; Bowen et al., 2009), although in these contexts the evidence is still rather weak. Although mindfulness training is now being offered to and studied within a broad variety of diagnostic categories, the treatment groups usually are rather homogeneous as regards diagnosis. So far, few studies have been done on the feasibility and effectiveness of mindfulness training in a heterogeneous patient group; we have found only two small studies in depressed/anxious samples (Green & Bieling, 2012; Ree & Craigie, 2007). Therefore, little is known about the applicability of offering mindfulness training to a mixed patient group. Moreover, knowledge about the differential effectiveness of such training in different diagnostic groups is limited, as no direct comparisons can be made between different diagnostic categories. The aim of this naturalistic outcome study was therefore to examine outcome following mindfulness training in a heterogeneous psychiatric outpatient population and to explore whether outcome differs in patients from different diagnostic categories. We hypothesized that mindfulness training would be associated with improvement in this heterogeneous patient group: We expected a reduction in the number of psychological symptoms, improvement in quality of life, and an increase in the level of mindfulness. We did not expect a differential outcome for patients from different diagnostic categories. Participants Method Outpatients attending mindfulness training at the Center for Integrative Psychiatry (CIP) in Groningen, the Netherlands between 2006 and 2009 were subjects in this study. Inclusion criteria for participation in the training were as follows: aged 18 years or older; a stable psychiatric disorder (i.e. no current severe depressive episode, no current psychotic episode, and no current [hypo]mania: sufficient stability for the patient to attend the sessions and do the homework practices); no alcohol or drug dependence; reasonable expectations of the training; motivation and willingness to do assigned homework; ability to participate in a group; and no practical or physical impediments that would preclude following the training. On the basis of a clinical intake interview, a psychiatrist made the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM-IV) diagnosis and assessed the other inclusion criteria by explicitly discussing the training s objective and evaluating potential obstacles for successful participation. A total of 233 patients participated in the training between 2006 to 2009, 214 of whom agreed to participate in the study and complete the pretraining questionnaires (92%). At the end of the training, 143 patients completed the posttraining questionnaires (i.e. 67% of 214). No systematic record was kept of how many of the 71 noncompleters (33%) did complete the mindfulness training, but dropout percentages for this training at our center tend to be about 7.5%. The noncompleters did not differ from the completers with respect to age, t(212) = 0.41, p = 0.684, illness duration, t(187) = 1.15, p = 0.250, gender, χ 2 (1) = 0.11, p = 0.742, education, χ 2 (2) = 1.49, p = 0.475, having a partner, χ 2 (1) = 1.10, p = 0.294, or diagnostic category, χ 2 (4) = 3.31, p = The noncompleters and completers also did not differ with respect to their pretreatment scores on the outcome measures, except for the Awareness subscale of the Kentucky Inventory of Mindfulness Skills, t(179) = 2.05, p = 0.042: noncompleters scored a little higher on this subscale, mean (standard deviation) = 27.8 (5.7) versus 26.0 (5.4).

3 Mindfulness in a Heterogeneous Sample 3 Measures Outcome data were collected at pretreatment and posttreatment assessments by means of questionnaires addressing symptomatology, quality of life, and mindfulness skills. Demographic data were collected at the pretreatment assessment by means of a questionnaire. Short Symptom List (SSL). The SSL (Dutch: Korte Klachten Lijst, KKL) is a selfreport questionnaire of 13 items about the degree to which respondents suffer from common psychological symptoms, like anxiety, depression, sleeping problems, and addiction (Lange & Appelo, 2007). For this study, an extra item was included regarding (hypo)manic symptoms. Scores for each item can range from 0 (not at all)to4(very much). The total SSL score therefore varies from 0 to 56. The reliability and validity of the SSL are satisfactory to good (Lange & Appelo, 2007). The SSL is a proper short alternative for the Symptom Checklist-90; total scores on these measures are highly correlated (Appelo & Lange, 2007). World Health Organisation Quality of Life-Bref (WHOQOL-Bref). The WHOQOL-Bref aims to measure quality of life (De Vries & Van Heck, 1996; De Vries & Van Heck, 2003; Trompenaars, Masthoff, Heck, Hodiamont, & Vries, 2005). It contains 26 items, 24 of which can be classified into four domains: (a) Physical health, (b) Psychological health, (c) Social relationships and (d) Environment. The other two items, regarding overall quality of life and general health, are combined in a facet (Overall Quality of Life and General Health [Overall QoL & GH]). Item scores range from 1 to 5. Total scores on the different domains and the facet range from 4 to 20, with higher scores denoting higher quality of life. The reliability and validity of the WHOQOL-Bref are satisfactory to good (Trompenaars et al., 2005). Kentucky Inventory of Mindfulness Skills (KIMS-39). The KIMS-39 measures the degree of mindfulness (Baer, Smith, & Allen, 2004; Baer et al., 2008) with 39 questions in four subscales. The Observe subscale questions the ability to perceive or notice internal stimuli (feelings, thoughts, physical sensations) and external stimuli (e.g., noises). The Describe subscale investigates the ability to describe or label internal and external stimuli. The Act with awareness subscale measures how well the respondent can focus on and pay attention to the present moment. The Accept without judgment subscale measures whether the patient is able to accept present moment experiences without judging them. Item scores range from 1 (never true) to 5 (always true). Ranges for total scores for the different subscales are as follows: (Observe), 8 40 (Describe), (Act With Awareness), and 9 45 (Accept Without Judgment). The psychometric properties of the KIMS-39 are good (Baer et al., 2004; Baer et al., 2008). Training The mindfulness training comprised eight weekly sessions of 2 1/2 hours each, and a silent retreat session held between sessions 6 and 7. Each group comprised 12 to 16 participants. The training followed the format of the MBSR program as described by Jon Kabat-Zinn (Kabat-Zinn, 1990). Because a substantial proportion of the participants had been diagnosed with (recurrent) depression, the MBSR program in our center was combined with a number of core elements from the MBCT program (Segal, Williams, & Teasdale, 2002). This was done because MBCT elements are more specific in addressing skills relevant to depression, like disengaging from dysphoria-induced depressogenic thinking and dealing constructively with negative cognitions and self-critical thoughts (Teasdale et al., 2000; Segal et al., 2002). Some of the MBCT elements were integrated in the program as standard elements, while other ones were offered optionally in the handouts and homework assignments; participants were encouraged to choose from these optional elements according to their own needs and preferences. All sessions included the following: one or more formal mindfulness exercises (body scan, sitting meditation, yoga); a group-based discussion of patients experience of these practices; psychoeducation related to body-mind interaction, automatic versus mindful responses to stress, and communication; interactive group evaluation of homework assignments; and instructions

4 4 Journal of Clinical Psychology, xxxx 2013 regarding homework assignments for the following week. MBCT-specific elements in the core program included 3-Minute Breathing Space (standard and coping), Automatic Thoughts Questionnaire, and Developing an action plan (i.e., strategies for an adequate response to early warning signals). A full description of the structure and elements of each session of the program is outlined in a treatment protocol available from the authors upon request. Before starting the training, participants were instructed that the program would entail doing homework for 45 minutes to 1 hour every day. During the training, the trainers repeatedly reminded the participants how important this homework was and motivated them to do the assignments, in an encouraging, noncoercive way. The homework assignments comprised guided (audiotaped) mindfulness exercises (e.g. body scan, yoga exercises, sitting meditation, mountain meditation), informal exercises to integrate mindfulness skills in daily routines (e.g., eating, brushing teeth), and other MBSR exercises (e.g. Pleasant and unpleasant events calendars, Identification of nourishing activities, Stress diary), supplemented with selected MBCT exercises (e.g., Automatic Thoughts Questionnaire, Developing an action plan, 3-Minute Breathing Space). All participants received a workbook including a general instruction to the training, homework instructions for each session, a form for registering (experiences with) homework, and handouts related to the respective session themes selected from Dutch-language versions of the handbooks by Kabat-Zinn (1990) and Segal et al. (2002). A central theme in the exercises was nonjudgmental moment-to-moment awareness of cognitive, emotional, and bodily experiences, fostering a decentered stance and a more adaptive response to negative thoughts and feelings (Kabat-Zinn, 1982; Teasdale et al., 2000). Trainers Each of the mindfulness groups was led by one of two qualified mindfulness trainers. Both were fully trained in MBSR and MBCT and certified by the Dutch Association for Mindfulness-based Trainers (VMBN). Both had extensive meditation experience (15 years and 30 years, respectively) and were engaged in ongoing meditation practices, in personal as well as professional contexts (e.g., as teachers/supervisors at the Dutch Institute for Mindfulness and as leaders of retreats). One of these trainers was a psychiatrist and psychotherapist, while the other was a specialized psychiatric nurse and Vipassana meditation teacher who had spent 6 years in Asia as a Buddhist monk. They had offered MBSR and MBCT in mental health care settings from the very first introduction of these programs in Dutch mental health care (2005) and are considered two of the Dutch pioneers in this regard. Both trainers were trained and supervised by experienced teachers from the United States and the United Kingdom and had ongoing intervision with other senior mindfulness trainers in the Netherlands. In about half of the training groups, the mindfulness trainers were assisted by one of three cotrainers (a nurse practitioner, a specialized psychiatric nurse, and a psychomotor therapist). All co-trainers had many years of experience as mental health care workers and had received a basic training in MBSR/MBCT for mental health care professionals. The co-trainers were supervised by the two main trainers and had regular intervision with each other under supervision of one of the main trainers. During these supervision and intervision meetings, adherence to the treatment protocol was monitored and problems were discussed. Procedure Prior to the training, patients were invited to participate in the study by means of a letter. After replying in the affirmative, they signed an informed consent and completed the pretraining questionnaires at home. Immediately after the training they were given the same questionnaires (posttreatment assessment) to be filled out at home and sent back by mail. Distribution and collection of the questionnaires was done by the mindfulness trainers, as part of a routine outcome measurement procedure. For this reason, no particular effort was made to increase response percentages.

5 Mindfulness in a Heterogeneous Sample 5 Statistical Analysis Primary analyses were performed on data of the completers sample (N = 143). KIMS data were available for only 100 patients; the KIMS questionnaire was not yet included in the study battery during the first year of the study. Differences between completers and noncompleters on baseline demographic and clinical variables were tested using independent t tests for continuous variables and chi-square tests for categorical variables. Because a completers analysis may produce biased estimates, sensitivity analyses were done in the intention-to-treat (ITT) sample (N = 214), using the last observation carried forward (LOCF) approach. LOCF is usually applied only for subjects who completed at least one follow-up measurement (Julious & Mullee, 2008), but because our study had only one follow-up measurement, all patients with missing data would have to be excluded, unless the baseline was included in the LOCF analysis (BOCF). Undertaking a BOCF analysis is counterintuitive because baseline scores cannot be influenced by treatment, and natural improvement due to regression to the mean and spontaneous recovery is not accounted for in baseline scores (Julious & Mullee, 2008). So, BOCF is likely to produce rather conservative results. In spite of this, we performed this sensitivity analysis to present a more balanced picture of the results. Based on their primary diagnosis, the patients were classified in five diagnostic categories: depressive disorder, bipolar disorder, anxiety disorder, adjustment disorder, and other. Classification of the groups was guided by the number of patients having a particular diagnosis; every diagnosis was considered a separate category, except diagnoses that were too infrequent, which were grouped into the category Other. All continuous variables were tested for normality with the Kolmogorov-Smirnov test and by inspection of the distribution plots. Non-normally distributed variables were logtransformed. This was the case only for the variable illness duration. The effectiveness of the mindfulness training was tested using repeated measures analysis of variance (ANOVA), in which the change from pretreatment to posttreatment on the outcome measures was investigated in the entire sample (using models with Time as predictor) as well as in the different diagnostic categories (using models with Time, Diagnostic category, and the interaction Time Diagnostic category as predictors). In the latter model, a significant interaction between Time and Diagnostic category implies that the effect of the training is different for different diagnostic categories. Post hoc tests for effectiveness within diagnostic categories were performed only in case of a significant interaction effect. In a secondary series of analyses, we investigated whether observed differences in effectiveness could be explained by baseline differences between the diagnostic categories. To analyze whether the various diagnostic groups differed on baseline demographic and clinical variables, we used independent t tests for continuous variables and chi-square tests for categorical variables. Variables that were unevenly distributed over the different diagnostic categories were subsequently included in the repeated measures ANOVAs to investigate whether they reduced the significance of the interaction Time Diagnostic category. Analyses were done in SPSS 18. A two-tailed alpha level of 0.05 was used. Patient Characteristics Results Mean age of the completers sample was 45.5 years (standard deviation [SD] 10.5, range 21 66). The majority of the participants were female (n = 99, 69%). Educational level of the sample was rather high; almost half of the sample had a higher education (higher vocational education/university; n = 68, 47.6%). The participants differed widely in illness duration: for some participants, the mindfulness training was the first contact they had with a mental health care institute; on the other hand, for one participant the first contact had been 34 years ago. Median illness duration was 8 years. A small majority of the participants had a partner (n = 88, 61.5%).

6 6 Journal of Clinical Psychology, xxxx 2013 Table 1 Overall Results for the Mixed-Patient Group (N = 143) Pretreatment Posttreatment F-test for change Outcome measure M (SD) M (SD) n F p Cohen s d SSL 15.2 (7.1) 11.8 (7.0) < WHOQOL-Bref Physical health 12.9 (2.6) 14.1 (2.8) < Psychological health 12.3 (2.4) 13.1 (2.3) < Social relationships 13.1 (3.5) 13.5 (3.3) Environment 14.9 (2.4) 15.4 (2.5) Overall QoL and GH 12.3 (3.0) 13.6 (3.3) < KIMS Observe 39.2 (7.6) 43.5 (6.0) < Describe 26.1 (7.0) 28.4 (5.8) < Act with awareness 25.6 (5.4) 28.9 (5.2) < Accept without judgment 26.6 (6.5) 30.4 (7.6) < Note. M = mean; SD = standard deviation; SSL = Short Symptom List; WHOQOL-Bref = World Health Organization Quality of Life Bref; Overall QoL and GH = Overall Quality of life and General Health; KIMS = Kentucky Inventory of Mindfulness Skills. The most frequently occurring primary diagnosis in the completers sample was depressive disorder (single episode or recurrent; n = 45, 31.5%), followed by bipolar disorder (type I or II; n = 42, 29.4%), anxiety disorder (generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, posttraumatic stress disorder, social phobia, or anxiety disorder not otherwise specified; n = 17, 11.9%), and adjustment disorder (n = 14, 9.8%). The remaining participants (n = 25, 17.5%) had a primary diagnosis of another category (including psychotic disorder, relationship problems, dysthymic disorder, personality disorder, attention deficit hyperactivity disorder, identity problem, hypochondriasis, or occupational problem). A hundred and one patients were diagnosed with one disorder, 35 patients had two disorders, and seven patients had three or more disorders. Most frequently co-occurring diagnosis was a personality disorder (n = 18), followed by anxiety disorder (n = 7), depressive disorder (n = 5), and alcohol abuse or dependency (in remission) (n = 5). Overall Outcome We first examined outcome after the mindfulness training in the entire patient group. Table 1 presents the results. On average, the participants showed improvement on all outcome measures. The repeated measures ANOVAs showed that these improvements were all significant. Effect sizes (Cohen s d), calculated by dividing the mean difference between the pretreatment and posttreatment scores by the standard deviation of the pretreatment scores, were small to moderate. Smallest effect size was observed for the Social Relationship subscale of the WHOQOL-Bref (d = 0.11). Largest effect size was for the Act With Awareness subscale of the KIMS (d = 0.61). As a sensitivity analysis, we repeated the analyses in the ITT sample (N = 214), with the baseline observation carried forward for the subjects with missing values at the posttreatment assessment. As could be expected, effect sizes were lower in the ITT analyses, though p-values were essentially the same, presumably due to an increase in power. Significant improvement was still observed on all outcome measures: SSL, F(1,209) = 32.2, p < 0.001; WHOQOL Physical health, F(1,210) = 34.8, p < 0.001; WHOQOL Psychological health, F(1,212) = 24.3, p < 0.001; WHOQOL Social relationships, F(1,212) = 4.5, p = 0.034; WHOQOL Environment, F(1,212) = 10.2, p = 0.002; Overall QOL & GH, F(1,213) = 25.6, p < 0.001; KIMS Observe, F(1,180) = 40.7, p < 0.001; KIMS Describe, F(1,186) = 25.2, p < 0.001; KIMS Act with awareness, F(1,180) = 27.5, p < 0.001; and KIMS Accept without judgment, F(1,180) = 32.4, p <

7 Table 2 Effect Sizes by Diagnostic Category Mindfulness in a Heterogeneous Sample 7 Pretreatment to posttreatment change (Cohen s d) Depression Bipolar Anxiety Adjustment Other Outcome measure n = 45 n = 42 n = 17 n = 14 n = 25 SSL WHOQOL Physical health Psychological health Social relationships Environment Overall QoL and GH KIMS n = 39 n = 15 n = 15 n = 11 n = 20 Observe Describe Act with awareness Accept without judgment Note. SSL = Short Symptom List; WHOQOL-Bref = World Health Organization Quality of Life Bref; Overall QoL and GH = Overall Quality of life and General Health; KIMS = Kentucky Inventory of Mindfulness Skills. Differential Outcome for Different Diagnostic Categories? Next, we investigated whether there was evidence for differential outcome for participants from different diagnostic categories. The interaction Time Diagnostic category was significant in the models for SSL, F(4,134) = 2.8, p = 0.028, WHOQOL Environment, F(4,137) = 2.6, p = 0.040, and Overall QoL and GH, F(4,138) = 3.3, p = This implies that improvement with respect to these subscales was different for the different diagnostic categories. Post hoc tests showed that the bipolar category did not improve significantly on the SSL, WHOQOL Environment, and Overall QoL and GH. The other diagnostic categories did improve significantly on these outcome measures, with one exception: The patients from the Anxiety category did not improve significantly on the Environment subscale of the WHOQOL. Table 2 presents the effect sizes for the change from pretreatment to posttreatment for each diagnostic category separately. This table shows substantial differences in effect sizes, also for scales for which the interaction Time Diagnostic category was not significant. However, we did not perform post hoc tests for the latter scales because the absence of a significant interaction between time and diagnostic category did not justify doing so. The absence of such an interaction effect implies that there is no evidence for differential outcome with respect to these outcome measures. Potential Covariates Explaining the Difference in Outcome Given the finding that participants of some diagnostic categories, particularly the bipolar, showed less improvement than participants of other categories, we investigated whether there were differences in demographic or clinical characteristics between the diagnostic categories that could explain these differences in improvement. To this end, we first tested whether participants from different diagnostic categories differed from each other with respect to age, gender, educational level, having a partner, illness duration, or baseline severity on the outcome measures. There was a clear and significant difference in illness duration, one-way ANOVA; overall F(4,126) = 5.47, p < 0.001: Illness duration was higher in the bipolar category compared with the other diagnostic categories. Further, we found a difference in the baseline scores on the SSL, overall F(4,135) = 3.05, p = Bipolar patients had lower SSL scores than the other diagnostic categories.

8 8 Journal of Clinical Psychology, xxxx 2013 Thus, the bipolar category diverged from the other categories in having a longer illness duration and a lower baseline symptom severity. To investigate whether these differences could explain the differences in improvement after the training, we included the variables for illness duration and baseline SSL scores as covariates in the repeated measures ANOVA models to see whether this would reduce the interaction Time Diagnostic category. This was indeed the case. In all models, the interaction effect was reduced and turned into nonsignificance after inclusion of the covariates. Illness duration appeared to account for the largest part of this reduction. A significant interaction between Illness duration and Time was found in the models for SSL, F(1,95) = 8.50, p = 0.004, and WHOQOL Environment, F(1,95) = 6.15, p = 0.015, and a trend was found in the model for Overall QoL and GH, F(1,95) = 3.41, p = In the model for SSL, the baseline SSL score also accounted for a substantial reduction in the interaction Time Diagnostic category. A significant interaction between Baseline SSL score and Time was found in this model, F(1,95) = 38.0, p < Inspection of the nature of these interaction effects revealed that participants with longer illness duration showed less improvement on the SSL, WHOQOL Environment, and Overall QoL and GH. Lower baseline SSL scores were related to less improvement on the SSL. Thus, the lower effectiveness of the mindfulness training in the bipolar category could be explained by the fact that participants from this category had a longer illness duration and a lower baseline symptom severity. Discussion We examined outcome following mindfulness training in a heterogeneous psychiatric outpatient population. The results showed that this mixed patient group improved on all outcome measures; i.e., significant reductions in psychological symptoms were found, as well as improvement in five domains of quality of life and in four different mindfulness skills. Differential improvement for different diagnostic groups was observed for psychological symptoms and environmental and overall quality of life. Bipolar patients showed less improvement on these outcomes compared with patients from other diagnostic categories. These differences appeared to be attributable to differences in illness duration and baseline symptom severity; in the bipolar patient group, illness duration was longer and baseline severity was lower. Mindfulness Training in a Heterogeneous Patient Group Our study lends support to the notion that mindfulness training delivered in a heterogeneous patient group can be effective. To our knowledge, only two other studies have reported previously on the effectiveness of mindfulness training in a mixed-patient group (Green & Bieling, 2012; Ree & Craigie, 2007). The sample sizes of these studies, however, were low (23 and 26, respectively), so no direct comparisons could be made between diagnostic groups. Moreover, the diagnoses included in these studies were all in the depression and anxiety spectrum. Our study group was truly heterogeneous; it included patients with various types of diagnoses. The results are in line with expectations of our mindfulness trainers, in whose clinical experience delivering mindfulness training in such a heterogeneous group is both effective and feasible. In their opinion, the combination of MBSR and MBCT elements in our program has added value in such a mixed group because it allows for a flexible approach so that details of the program can be adapted to the various patient needs. The trainers also report some advantages of administering mindfulness in a heterogeneous group; by hearing other patients talk about their complaints, participants tend to disengage from their own complaints. As a result, the training is lifted to a more transdiagnostic level in which living life as a human being rather than living with this or that disorder is the issue. While the training may not be suitable for all psychiatric patients patients with a current severe depressive episode, psychotic episode, (hypo)mania, or substance dependence are excluded from the training in our center the results do support the notion that the scope of mindfulness training may be expanded to a wider variety of patients and that group formats do not need to be homogeneous.

9 Effectiveness in Different Diagnostic Groups Mindfulness in a Heterogeneous Sample 9 Our study showed significant improvements in patients from all diagnostic categories. Evidence for the effectiveness of mindfulness training in depressed patients is not new; convincing results have been reported in several studies (Fjorback et al., 2011; Piet & Hougaard, 2011; Van Aalderen et al., 2012; Chiesa & Serretti, 2011), although these results mainly concerned remitted patients. There are also some reports on the effectiveness of mindfulness training in patients with anxiety disorders (Hofmann et al., 2010; Kim et al., 2010a, 2010b; Lovas & Barsky, 2010; Williams et al., 2011), although this evidence is moderate or the studies had small sample sizes. Our results add to this evidence, showing improvements after the training in the anxious patient group. We have not found any effect studies of mindfulness training in patients with an adjustment disorder, despite the fact that this disorder is rather common in both adolescents and adults and may have severe consequences (Casey, 2009; Semprini, Fava, & Sonino, 2010). Casey argues that underinvestigation of adjustment disorder treatment may be because of the fact that there are problems with the diagnostic criteria. Our results show that patients diagnosed with adjustment disorder do improve after mindfulness training. Patients with bipolar disorder appeared to be atypical in our study. They seemed to derive the least benefit from the training. Although they did improve on some of the measures, for example, psychological QoL and mindfulness skills, effect sizes for this category were generally lower than for the other diagnostic categories. On three of the outcome measures the improvements of the bipolar patients were not significant at all. Our covariance analyses showed that this patient group diverged from the other groups also in other aspects: Illness duration was relatively high and baseline symptom severity was relatively low. These differences seemed to account for the differences in outcome. So, our results do not necessarily imply that mindfulness training is unsuitable for patients with bipolar disorder; the training might have led to improvements in bipolar patients with a shorter history of mental health problems and/or more severe problems at baseline. Also, the value of the training for bipolar patients may lie in relapse prevention rather than symptom reduction; clinical experience at our center suggests this may be the case, but the follow-up time of our study was too short to substantiate this. The literature does present some evidence for the effectiveness of mindfulness training in bipolar patients (Williams et al., 2008; Deckersbach et al., 2012; Stange et al., 2011). None of these studies, however, had a no-treatment control condition and sample sizes were low. Overall effect sizes for the changes observed in our study were small to medium, depending on the outcome measure (e.g., effect sizes were typically low for social relationships, which is often the case in outcome studies because improvements in interpersonal skills take time to produce an effect; Howard, Lueger, Maling, & Martinovich, 1993). Effect sizes calculated for the different diagnostic categories were rather diverse, ranging from 0 to We doubt whether these differences are solely because of diagnostic differences. Our results suggest that illness characteristics such as disease history and symptom severity are more important in predicting the success of the training. Presumably, other baseline demographic and clinical characteristics as well as differences in personality and motivation (e.g., willingness to perform daily home practices) play a role (e.g., Bowen & Kurz, 2012; Shapiro, Oman, Thoresen, Plante, & Flinders, 2008; Vettese, Toneatto, Stea, Nguyen, & Wang, 2009). Therefore, allocation of patients to mindfulness training should probably be guided by other indices than DSM-IV diagnoses. More research is needed to substantiate this supposition. Limitations and Strengths A number of limitations of the current study should be mentioned, the absence of a control group being the most obvious one. Because of this, we cannot be certain whether the observed changes can be ascribed to the mindfulness training. However, for the comparison between the different diagnostic categories, this point is less of a problem. Another limitation is the lack of a follow-up assessment, which precludes conclusions about the sustainability of the observed changes. A further weakness is that medication use was not controlled for.

10 10 Journal of Clinical Psychology, xxxx 2013 Finally, it should be mentioned that there was a large number of noncompleters (33%). This high attrition rate can largely be attributed to the fact that the study was performed in the context of a routine outcome monitoring procedure. There was no special research team in charge of the data collection and therefore no specific efforts were made to increase the number of responses. In terms of routine outcome monitoring, the response percentage is actually rather high (e.g. Happell, 2008). The fact that no differences were found between noncompleters and completers and that the observed changes were still significant in ITT analyses with the baseline observation carried forward strengthens our confidence in the validity of our results. A strong feature of the study is its naturalistic design. All patients who were given the training were eligible for the study and no restrictions were made with regard to other therapies or medication. Therefore, generalizability of the results to real clinical practice is very high. Another strength is the fact that in our study a direct comparison could be made between diagnostic categories. To our knowledge, this is the first study in which this has been possible. Clearly, our results need replication. It would be interesting to see future studies comparing a mixed patient group with a homogeneous patient group, preferably in a randomized design. This may yield better insight into whether mindfulness training in a heterogeneous patient group is as effective as it is in a single diagnosis group. Further, future studies comparing effectiveness in different diagnostic categories may benefit from a better match of patients on characteristics like illness duration and baseline severity, and from including long-term assessments. References Appelo, M., & Lange, A. (2007). Meten van klachten en veerkracht in vierentwintig vragen. Directieve Therapie, 27(3), Baer, R. A. (2009). Self-focused attention and mechanisms of change in mindfulness-based treatment. Cognitive Behaviour Therapy, 38, S1, Baer, R. A., Smith, G. T., & Allen, K. B. (2004). Assessment of mindfulness by self-report The Kentucky Inventory of Mindfulness Skills. Assessment, 11(3), Baer, R. A., Smith, G. T., Lykins, E., Button, D., Krietemeyer, J., Sauer, S.,... Williams, J. M. (2008). Construct validity of the five-facet mindfulness questionnaire in meditating and nonmeditating samples. Assessment, 15(3), Bishop, S. R., Lau, M., Shapiro, S., Carlson, L., Anderson, N. D., Carmody, J.,... Devins, G. (2004). Mindfulness: A proposed operational definition. Clinical Psychology-Science and Practice, 11(3), Bowen, S., Chawla, N., Collins, S. E., Witkiewitz, K., Hsu, S., Grow, J.,... Marlatt, A. (2009). Mindfulnessbased relapse prevention for substance use disorders: a pilot efficacy trial. Substance Abuse, 30, Bowen, S., & Kurz, A. S. (2012). Between-session practice and therapeutic alliance as predictors of mindfulness after mindfulness-based relapse prevention. Journal of Clinical Psychology, 68(3), Casey, P. (2009). Adjustment disorder epidemiology, diagnosis and treatment. Cns Drugs, 23(11), Chiesa, A., & Serretti, A. (2011). Mindfulness based cognitive therapy for psychiatric disorders: A systematic review and meta-analysis. Psychiatry Research, 187(3), De Vries, J., & Van Heck, G. L. (1996). De Nederlandse versie van de WHOQOL-bref. Tilburg: Universiteit van Tilburg. De Vries, J., & Van Heck, G. L. (Eds.). (2003). Nederlandse handleiding van de WHOQOL [Dutch Manual of the WHOQOL]. Tilburg: Universiteit van Tilburg. Deckersbach, T., Hoelzel, B. K., Eisner, L. R., Stange, J. P., Peckham, A. D., Dougherty, D. D.,... Nierenberg, A. A. (2012). Mindfulness-based cognitive therapy for nonremitted patients with bipolar disorder. Cns Neuroscience & Therapeutics, 18(2), Fjorback, L. O., Arendt, M., Ornbol, E., Fink, P., & Walach, H. (2011). Mindfulness-based stress reduction and mindfulness-based cognitive therapy A systematic review of randomized controlled trials. Acta Psychiatrica Scandinavica, 124(2), Green, S. M., & Bieling, P. J. (2012). Expanding the scope of mindfulness-based cognitive therapy: Evidence for effectiveness in a heterogeneous psychiatric sample. Cognitive and Behavioral Practice, 19(1),

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