As shown in , most of the randomized participants (72%) were male, single or divorced (76%), did not have a college degree (76%), and were not employed full-time (72%). The majority met the DSM-IV criteria for alcohol dependence (68%) and/or cocaine dependence (48%). Analysis of variance and chi-square analysis indicated no significant differences by treatment condition except marital status (57% married in CBT versus 6% married in MT, p = .02). No differences in baseline drug or alcohol use were found between treatment completers (N = 14) and non-completers (N = 22). Among treatment completers, although substance use in the month prior to treatment initiation was reported by twice as many subjects in the MT (8/9) compared to the CBT group (2/5), it did not differ by group status at baseline ().
Baseline demographics and substance use. GED = general educational development diploma, HS = high school, DSM = Diagnostic and Statistical Manual of mental disorders, MJ = marijuana
Feasibility: treatment retention and satisfaction
To evaluate the feasibility and acceptability of MT relative to CBT, we compared treatment retention (defined as treatment drop-out) and satisfaction across the two treatment conditions. Of the 36 individuals who entered the study, 9/21 (43%) completed MT, while 5/15 (33%) completed CBT (p = .56, ). Participants who initiated treatment (N=25) attended 65% of sessions in MT vs. 34% of sessions in CBT group (F = 4.89, p = .04). Participants who completed treatment (N=14) in both groups rated their treatments as highly satisfactory as assessed by TCS (4.2 ± 0.5 versus 4.4 ± .5 of 5, p = .37).
Substance use outcomes
No differences in alcohol and cocaine use were found during the treatment period but trended toward favoring the CBT group (in MT vs. CBT groups, self-reported % days of cocaine use: 5.4 ± 8 versus 0.0 ± 0.0, p = .17; and alcohol use: 24.3 ± 28 vs. 0.0 ± 0.0, p=0.09). No side effects or adverse events were noted.
Specificity of MT: Effects of Treatment on Mindfulness Skills Acquisition and Implementation
To determine whether our paradigm adequately fostered mindfulness skills development, we measured the FFMQ scores before and after treatment. At baseline, there were no observed differences in the FFMQ between groups regarding all enrolled participants (MT = 127 ± 26, CBT = 123 ± 23, p = .64) as well as treatment completers only (MT = 122 ± 26, CBT = 119 ± 29, p = .82).
Treatment completers in both MT and CBT groups showed significantly increased FFMQ scores over time. Although participants in the MT group showed tendency toward greater overall increases in FFMQ scores compared to CBT after treatment, these differences did not reach statistical significance (MT = 144 ± 18; CBT = 131 ± 27, p = .04 by time, p = .54 group by time).
Specificity of MT: Subjective and Objective Responses to Stress Provocation
To determine if MT differentially influenced psychological responses to stress, we compared responses to a personalized stress challenge in treatment completers. Participants who received MT reported significantly attenuated anxiety in both anxiety Likert scales and DES anxious subscale scores (Stress minus Neutral Anxiety: 1.5 ± 2.1 vs. 4.6 ± 1.5, p = .01, ; DES: 1.5 ± 3.9 vs. 7.0 ± 3.8, p = .03, ). Though not statistically significant, individuals receiving MT also reported about half the stress-induced drug craving compared to those receiving CBT (1.1 ± 3.7 vs. 2.0 ± 3.1, p = .65, ). These attenuations were echoed in several other negative emotion scores, such as sadness, anger and fear ().
FIGURE 2 Anxiety and Drug Craving During Stress Provocation (MT, n = 8; CBT, n = 5). Y axis denotes reported anxiety scores after listening to personalized neutral or stressful stories. a) Anxiety severity scores: far right indicates normalized scores (stress (more ...)
Emotional Responses During Stress Provocation (MT, n = 8; CBT, n = 5). Y axis denotes normalized Differential Emotion Scale scores after stress provocation (stress minus neutral). * indicates p ≤ .05 between treatment groups.
We also sought to determine if MT, compared to CBT, differentially influenced physiological measures of stress. As expected, we found large differences in galvanic skin responses between stress and neutral stories, however, they were not different between groups (MT = 10.0 ± 8.2 vs. 4.5 ± 7.4; CBT = 7.0 ± 6.4 vs. 0.8 ± 1.1, F = 12.36, p = .01 for condition). However, no increases in maximum HR were seen in the MT group during stress, where these expected increases were observed in the CBT group (MT = 81.4 ± 7.0 vs. CBT = 98.7 ± 37.6, p = 0.19, ). Although these findings were not significant, the partial eta squared indicated this effect size to be large (.15). Corresponding differences were seen in heart rate variability measures: individuals in the MT group showed decreased sympathetic/vagal ratios compared to the CBT group (MT = 4.0 ± .5 vs. CBT = 4.2 ± .2, F = 7.97, p = 0.02, effect size = .42, ).
FIGURE 4 Maximum Heart Rate and Autonomic Nervous System Tone During Stress Provocation (MT, n = 8; CBT, n = 5). a) Maximum heart rate during neutral and stressful stories. b) Percent change in sympathetic/vagal ratio during stress versus neutral stories. * indicates (more ...)