Temporal Changes in Mindfulness Skills and Positive and Negative Affect and Their Interrelationships During Mindfulness-Based Cognitive Therapy for Cancer Patients

Participants were recruited through various online (for example, Facebook) and offline (for example, newspapers) media outlets. Interested participants could self-enroll on the study website, and inclusion criteria were verified via telephone. Inclusion criteria were as follows: (1) having a diagnosis of any type of cancer; (2) experiencing at least mild psychological distress (a score of ≥ 11 on the Hospital Anxiety and Depression Scale (HADS); Spinhoven et al., 1997; Zigmond & Snaith, 1983); (3) computer literacy and internet access; (4) good command of the Dutch language; and (5) willingness to participate in either the face-to-face or internet-based mindfulness intervention. Exclusion criteria were the following: (1) severe psychiatric morbidity such as classifications with a high risk for psychosis like bipolar disorder, schizophrenia spectrum, and other psychotic disorders and a high risk for current suicidality (suicide-related behaviors with suicidal intent). Potential participants were directly asked whether severe psychiatric morbidity was present in the telephone screening. In the baseline assessment, the Structural Diagnostic Interview for DSM-IV (SCID-IV; First et al., 1997; Spitzer et al., 1992) was used to verify the (1) absence of severe psychiatric morbidity (more on the use of the SCID-IV below); (2) change in psychotropic medication within 3 months of baseline; and (3) current or previous participation in MBCT or MBSR. Patients provided written informed consent prior to participation. More details about the recruitment procedure can be found elsewhere (Compen et al., 2015).

In total, 245 patients were included in the BeMind project. The current study included only patients (n = 163; 67%) who completed at least four sessions of MBCT (n = 84) or eMBCT (n = 79) (Kuyken et al., 2008; Teasdale et al., 2000). Descriptive statistics on these groups can be found in Table 1. There were no statistically significant differences in gender, age, education level, type of cancer, time since diagnosis, psychiatric diagnosis (depression/anxiety), baseline distress or mindfulness, and positive and negative affect between participants who completed at least four sessions vs. participants that dropped out of the intervention, and between participants randomized to MBCT vs. eMBCT. Intervention completion did not significantly differ between MBCT (70%) and eMBCT (63%). Participants in eMBCT completed significantly more sessions (M = 8.5; SD = 1.4) than those in in the MBCT condition (M = 7.8; SD = 1.3).

Of the included 163 patients, 85% (n = 138) were female, and the mean age was 52 years (SD = 10 years). Most participants were highly educated (n = 115; 71%). The majority had breast cancer (n = 103; 63%). Most patients were treated with curative intent (self-reported); that is, their treatment focused on full recovery, rather than palliation (n = 142; 87%). On average, participants received a cancer diagnosis more than 3 years ago (M = 3.4 years, SD = 4.7 years). Patients were moderately distressed when entering this study (score on Hospital Anxiety and Depression Scale (Spinhoven et al., 1997; Zigmond & Snaith, 1983); M = 17.8, SD = 6.9).

Presence of a depression or anxiety disorder was established with the relevant modules of the SCID-IV (First et al., 1997; Spitzer et al., 1992). Anxiety disorders included panic disorder, agoraphobia, social anxiety disorder, specific phobia, and generalized anxiety disorder. The SCID-IV was administered by a trained interviewer who completed a Master in Behavioral Science degree (F.C.), supervised by either an experienced psychiatrist (E.B. or A.S.) or psychologist (M.v.d.L.). All interviews were audiotaped. Based on the SCID-IV, 31 patients (19%) suffered from depression, and 16 patients (10%) had an anxiety disorder (generalized anxiety disorder: n = 6; specific phobia: n = 3; panic disorder: n = 1; social phobia: n = 1; other: n = 5). For more details, see Compen et al. (2018).

The current study reports secondary analyses of data from the BeMind project, a multicenter, three-armed randomized controlled trial in distressed cancer patients comparing group face-to-face MBCT and individual internet-based eMBCT with a treatment as usual (TAU) group (Cillessen et al., 2018; Compen et al., 2015, 2018). Both MBCT and eMBCT outperformed TAU in reduction of psychological distress (Compen et al., 2018). The focus of the current study is on weekly measures obtained during MBCT and eMBCT. These measures were not obtained during TAU, because the main aim of the trial was to study effectiveness, and to minimalize burden for participants in TAU. Therefore, the current study only focused on the trial arms MBCT and eMBCT, and not on TAU.

MBCT and eMBCT were based on the MBCT program of Segal et al. (2013) and were similar in number of sessions, frequency, and content. The interventions were slightly adapted to fit the needs of cancer patients. Firstly, the psycho-education about stress was replaced by psycho-education about the different phases of grief. Furthermore, information about cancer-related physical symptoms such as fatigue was included. Finally, the movement exercises were adapted for patients with physical limitations, for example, edema. The 8-week (e)MBCT program included weekly sessions (group sessions in MBCT; written information, exercises, and therapist feedback in individual eMBCT). There was a 6-h silent retreat between session six and seven. Patients in eMBCT received instructions to organize their own 6-h silent retreat. Thus, there were nine sessions in total over a time span of 8 to 9 weeks. In addition to the sessions, patients were requested to meditate at home (45 min a day, 6 days a week).

In MBCT, sessions were conducted in face-to-face groups with a maximum of 12 patients per group. The eMBCT program was individual. In eMBCT, each participant was provided with information and exercises involving the theme of the session through a personal, secure webpage. Participants were encouraged to read the information and do the exercises within 1 week. Participants reflected on their experiences by keeping a personal log. The therapist assigned to each participant gave weekly feedback based on this log on a set day of the week, thereby guiding the patient through the program.

Both MBCT and eMBCT were taught by nine qualified mental health care professionals which were also experienced mindfulness teachers. All of them had previous experience with cancer patients and met the criteria of the UK Mindfulness-Based Teacher Network (UK Network for Mindfulness-Based Teachers, 2015). To assess adherence to the protocol and teacher competence, two randomly chosen videotaped sessions were assessed with the MBI-TAC (Crane et al., 2013) by two independent raters. Of the nine rated teachers, two were rated as beginner (22%), three as competent (33%), and four as proficient (44%). No teachers were rated as incompetent. The two teachers at the beginner level only taught one MBCT course each, and no eMBCT.

Prior to randomization, baseline questionnaires were completed. Participants completed the weekly questionnaires before each of the nine sessions of (e)MBCT. MBCT participants completed these questionnaires on paper at the beginning of each group session, while eMBCT participants completed the questionnaires digitally, when starting a new session in the online program.

Patients in the TAU condition were randomly allocated to MBCT or eMBCT after the 3-month TAU period. In the current study, we combined data of patients who were directly randomized to MBCT or eMBCT, and patients who received MBCT or eMBCT after TAU. Further details of the study procedures can be found in the study protocol (Compen et al., 2015).

The current study focused on data collected in week 1 through week 9 of the intervention. All questionnaires were completed each week. Mindfulness was measured with the Mindful Attention and Awareness Scale (MAAS; Brown & Ryan, 2003; Schroevers et al., 2008). The MAAS assessed different aspects of awareness and attention, which are seen as core characteristics of mindfulness (Brown & Ryan, 2003). It measures the frequency of mindful states. The MAAS has 15 items (“I find it difficult to stay focused on what’s happening in the present”) that can be answered on a 6-point Likert scale, from “almost never” to “almost always.” Higher scores represent higher levels of mindfulness. The MAAS was validated in an oncology sample (Carlson & Brown, 2005), and has good psychometric properties, including internal validity (MacKillop & Anderson, 2007; Schroevers et al., 2008). The average score was used in this study. Internal consistency in the current study was excellent (Cronbach’s α = 0.88; McDonald’s ω = 0.87).

Positive and negative affect were measured with the Positive and Negative Affect Scale – Short Form I (PANAS-SF; Engelen et al., 2006; Thompson, 2007; Watson et al., 1988). The PANAS-SF has 20 items that consist of ten positive and ten negative affective states (“excited” and “nervous”). For each affective state, participants had to indicate on a 5-point Likert scale (from “very slight to not at all” to “extremely”) whether they felt this way during the past week. Higher scores represent higher levels of positive and negative affect. Various psychometric aspects of the PANAS-SF including internal reliability, temporal stability, and convergent and criterion-related validities were rated as acceptable (Thompson, 2007). The average scale score was used in this study. Internal consistency in the current study was good for positive affect (Cronbach’s α = 0.79; McDonald’s ω = 0.78), and sufficient for negative affect (Cronbach’s α = 0.66; McDonald’s ω = 0.66).

To study intervention mechanisms, an adequate treatment dose is required (Kazdin, 2007). Therefore, the current study only included participants who completed at least four sessions of (e)MBCT, which is considered a sufficient dose in MBI literature (Kuyken et al., 2008; Teasdale et al., 2000). Data from participants in MBCT were obtained prior to the weekly group sessions, resulting in a 1-week interval between the questionnaires. From seven patients, one measurement was excluded from analyses because the questionnaires were completed after the group sessions instead of before, which could interfere with our results. In eMBCT, there was more variability in time between two measurements (M = 9.4 days, SD = 7.8 days), compared to MBCT. To ensure consistency in measurement timing, we excluded one measurement from 18 patients because the interval between assessments was less than 1 day or more than 4 weeks. Thus, we removed seven MBCT and 18 eMBCT datapoints, representing only 2.2% of all datapoints. The total percentage of missing data varied between 18 and 33% per measurement week. Therefore, we utilized analytic procedures that were capable of retaining participants with incomplete data (see below). Calculations of skewness (range 0.167 to 0.723) and kurtosis (range − 0.082 to 0.393) did not reveal any strong violations; therefore, no transformations were used. In the analyses, data of patients that followed MBCT or eMBCT after TAU were combined with data of patients that were initially randomized to MBCT or eMBCT, as there was no difference between these two groups on variables used in our data-analysis (mindfulness, positive and negative affect) or on psychological distress.

Descriptive statistics (means, standard deviations) were calculated in SPSS, version 22 (IBM Corp, 2013). Autoregressive latent trajectory (ALT) models (Bollen & Curran, 2004) were used to estimate latent intercepts and slopes, autoregressive, and cross-lagged effects for mindfulness and positive and negative affect in Mplus version 6 (Muthén & Muthén, 2015). In an ALT model, autoregressive and latent growth curve parameters are combined. This modeling approach enabled us to study general patterns over the 9 weeks (with latent intercepts and slopes) and week-to-week patterns (with autoregressive and cross-lagged paths) simultaneously. The first measurement covaried with the intercept and slope (instead of being part of the estimation of intercept and slope), which is common practice with ALT models to ensure lagged values can be interpreted correctly (Delsing & Oud, 2008; Morin et al., 2011) and to avoid the statistical problem of infinite regression (Morin et al., 2011). Therefore, the intercept should be interpreted as the general initial level accounted for week 1, to which we refer as general level. When performing the ALT models, full information maximum likelihood was employed so participants with incomplete data could be included in the analyzed sample (Enders & Bandalos, 2001).

Building an ALT model requires the fitting of a series of models with and without random slopes and various constraints to find a balance between fit and parsimony. The fit of the models was determined with χ², χ² divided by the degrees of freedom, (CMIN⁄df), the comparative fit index (CFI), the Tucker-Lewis index (TLI), the root mean square error of approximation (RMSEA), and the standardized root mean square residual (SRMR). For CMIN/df, values below 2 were considered to represent good fit. For CFI and TLI, values above 0.90 are considered adequate, while values above 0.95 are indicative of good fit (Hooper et al., 2008). Previously, RMSEA below 0.05 was a rule of thumb to indicate good fit. However, we followed new guidelines (Hooper et al., 2008) that suggest RMSEA values below 0.07 are indicative of good fit. Furthermore, based on our sample size, an optimal cutoff would lie between 0.05 and 0.06 (Sivo et al., 2006). For SRMR, values below 0.08 and 0.05 are considered adequate and good, respectively (Hooper et al., 2008).

The primary analyses included two multivariate ALT models. The first included mindfulness and positive affect, the second mindfulness and negative affect. We closely followed the analytical steps of Morin et al. (2011) for building the ALT models. We specified a series of increasingly complex models and used χ² difference tests to determine whether the more complex model improved the fit to the observed data. When the simpler model demonstrated a better fit (the improved fit of the more complex model was not statistically significant), the former model was retained and compared to subsequent models. Only the most parsimonious models that adequately fitted the observed data are reported here. In these final models, we controlled for intervention type (eMBCT vs. MBCT), by including intervention type as a dichotomous predictor of the latent intercept, slope parameters, and the week 1 measurement. The results of all tested models and all model comparisons are available in Supplementary Materials. All reported results reflect the standardized coefficients.

The conditional ALT model that demonstrated the best fit to the observed data for mindfulness and positive affect included three sets of equality constraints: all concurrent correlations between weekly measures, all autoregressive paths for positive affect, and all cross-lagged regression paths from positive affect to mindfulness. This model provided adequate to good fit to the observed data (χ²(139) = 202.5, p < 0.001; CMIN/DF = 1.46; CFI = 0.971; TLI = 0.964; RMSEA = 0.054; SRMR = 0.073). We focus our description of the results on model parameters pertaining to the latent structure (intercepts and slopes; Table 3), and autoregressive and cross-lagged regression paths (Fig. 1).

The conditional ALT model that demonstrated the best fit for mindfulness and negative affect included five sets of equality constraints: the concurrent correlations between weekly assessments, the autoregressive paths for mindfulness, the autoregressive paths for negative affect, and the cross-lagged paths from mindfulness to negative affect and the cross-lagged paths from negative affect to mindfulness. This model had adequate to excellent fit (χ² (153) = 215.0, p < 0.001; CMIN/DF = 1.41; CFI = 0.968; TLI = 0.964; RMSEA = 0.051; SRMR = 0.075). Again, we focus our description on model parameters pertaining to the latent structure (Table 4), and autoregressive and cross-lagged regression paths (Fig. 2).

The current study has several strengths. A major strength is the statistical model we used. The ALT models enabled us to simultaneously disentangle general and week-to-week patterns. Therefore, week-to-week patterns were controlled for general tendencies in the data, and the other way around. Without these controls, results could provide an incomplete or even incorrect picture of mechanisms (Voelkle, 2008). Specifically, we would not have been able to observe time-related differences in the association between mindfulness and negative affect when using regular mediation models. A second strength of the current study are the repeated measures of our mediators during the intervention.

Some limitations should be mentioned as well. We worked with weekly measures, as we could easily administer these at the start of the MBCT sessions. However, it is possible that the week-to-week timeframe was too crude, resulting in a lack of significant findings on cross-lagged paths. Day-to-day or even moment-to-moment assessments might be better able to capture the influence mindfulness and affect may have on each other (for example, Gotink et al., 2016; Snippe et al., 2015). Secondly, we lacked weekly measures of a control group, as we considered it to be too burdensome for patients in TAU to complete weekly measures. Therefore, we cannot be sure whether time patterns observed are due to (e)MBCT, or whether these are processes naturally occurring over time. However, we did find increases in mindfulness and decreases of psychological distress in eMBCT and MBCT compared to treatment as usual in the main RCT (Compen et al., 2018). Thirdly, some criticism has been expressed regarding the questionnaires we used. Although the MAAS is commonly used, its validity has been criticized due to statements being formulated in a negative way (reflecting mindlessness) and its restriction to measuring mindful attention and awareness (Grossman, 2011). The PANAS, on the other hand, has been criticized for including only high arousal emotions (Forgeard et al., 2011), while mindfulness especially increases lower arousal positive emotions, like calmness (Jones et al., 2018). Fourthly, although most involved mindfulness teachers were competent, two teachers were rated as beginner. They only provided MBCT for a small portion of participants (< 10). Finally, although the parent trial of this study has sufficient power (0.9; Compen et al., 2018), we did not do an a priori power analysis for these analyses. As a consequence, power may be compromised in our analyses.