Effects of repeated transcranial direct current stimulation on smoking, craving and brain reactivity to smoking cues

Abstract

Recent studies have shown that transcranial direct current stimulation (tDCS) may reduce craving and smoking. However, little is known regarding brain correlates of these behavioral changes. We aimed to evaluate whether 10 sessions of tDCS modulate cigarette consumption, craving and brain reactivity to smoking cues in subjects with tobacco use disorder (TUD). In a double blind parallel-arms study, 29 subjects with TUD who wished to quit smoking were randomly assigned to receive 10 sessions of either active or sham tDCS applied with the anode over the right dorsolateral prefrontal cortex (DLPFC) and a large cathode over the left occipital region. As compared to sham, active tDCS significantly reduced smoking craving and increased brain reactivity to smoking-cues within the right posterior cingulate, as measured with a functional magnetic resonance imaging event-related paradigm. However, we failed to find a significant difference between active and sham groups regarding the self-reported number of cigarettes smoked and the exhaled carbon monoxide during one month. These findings suggested that 10 sessions of tDCS over the right DLPFC may reduce craving by modulating activity within the resisting-to-smoke network but might not be significantly more effective than sham to decrease cigarette consumption.

Figure 1

Changes in cigarette consumption over time in both stimulation group (active, N = 17, and sham, N = 12). Cigarette consumption consisted in the day-by-day reported number of cigarettes smoked. The lines show the predicted values from the linear mixed-effects model. Dots show means from the data. Active stimulation is represented in black and sham stimulation is represented in grey. Values at Day 0 represent the baseline cigarette intake the day before the beginning of stimulation. Values at Day 1 to Day 5 represent the cigarette intake during the stimulation’s course (2 sessions by day). Values at Day 6 to Day 28 during the follow-up assessment. The figure has been plotted using R software [v.3.4.3] (R Core Team. R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org).

Figure 2

Box plots of the craving scores changes (Post-Pre) following transcranial Direct Current Stimulation (tDCS) in each stimulation group (active, N = 17, and sham, N = 12) regardless of the tDCS session. Active stimulation is represented in dark grey and sham stimulation is represented in white. Center lines show the medians; box limits indicate the 25th and 75th percentiles as determined by R software; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, crosses represent sample means. The figure has been plotted using R software [v.3.4.3] (R Core Team. R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org).

Figure 3

Axial and coronal views of brain reactivity to smoking vs. neutral cues in adults with tobacco-use disorder (N = 24). Significant clusters were overlaid on an anatomical MNI template. These analyses were performed at a voxel height threshold at P < 0.005 significance (minimum K = 85).

Figure 4

Sagittal, coronal and axial views of significant Group x Time interaction for the smoking versus neutral cues contrast. These analyses were performed at a voxel height threshold at p < 0.005 significance (minimum K = 85). The significant cluster was overlaid on an anatomical MNI template. The diagram depicts beta values extracted from the right posterior cingulate cluster for each time (pre and post) and group (active, N = 14 and sham, N = 10).