بررسی اثر رفتاردرمانی شناختی بر حجم مغز منطقه ای در بیماران هراس عنکبوتی: نتایج اولیه

Successful cognitive behavior therapy (CBT) for spider phobia is able to change patients’ brain activation during visual symptom provocation. The present voxel-based morphometry study investigated whether this therapy approach can additionally affect brain structure. We analyzed gray matter volume of 12 spider-phobic patients prior to CBT and in a six-month follow-up investigation, and contrasted the results with data from 13 non-phobic controls. CBT provoked a dramatic decrease in syndrome severity in the clinical group as indexed by self-report and by a behavioral approach test. This was accompanied by a reduction of left supplementary motor area volume, which was correlated with the reduction of symptom severity. The therapy-related decrease of left amygdala volume was marginally significant. Nevertheless, in both sessions the patients were characterized by increased amygdala volume relative to controls. Our findings have to be considered preliminary and need replication in a bigger sample.

Cognitive behavior therapy (CBT), including graduate exposure and cognitive restructuring, is the most effective intervention method for individuals suffering from spider phobia. Primary goals of this type of treatment are to reduce phobic anxiety, to eliminate avoidance and to alter negative automatic thoughts about the animal (Choy, Fyer, & Lipsitz, 2007). Successful CBT is able to change brain activation during visual symptom provocation in spider-phobic patients. A first waiting-list controlled neuroimaging investigation on short-term effects of CBT observed reduced activation of the anterior cingulate cortex (ACC) and the insula (Straube, Glauer, Dilger, Mentzel, & Miltner, 2006). This therapy-related activation decrease was interpreted to reflect normalization of somatic arousal. Schienle, Schäfer, Hermann, Rohrmann, and Vaitl (2007) conducted one-session CBT and taught spider-phobic patients to hold a living spider in their hands, which was associated with increased medial orbitofrontal cortex (OFC) activation directly after the therapy. The enhanced medial OFC activation during the viewing of spider pictures continued to be present in a 6-month follow-up investigation in the patients who were still able to show the learned approach behavior. Considering that the OFC is central for the relearning of stimulus-reinforcement associations (Kringelbach & Rolls, 2004), the main therapy effect was understood as cognitive restructuring with a new valence assignment to the phobic stimulus. Interestingly, only one study observed a reduction of phobia-related amygdala hyperactivation directly after exposure therapy (Goossens, Sunaert, Peeters, Griez, & Schruers, 2007). The mentioned brain imaging studies demonstrate that CBT is able to change brain activation of the afflicted patients in disorder-relevant situations. Whether this psychotherapy approach can also affect brain structure has not been studied thus far. We analyzed data acquired in two previously published magnetic resonance imaging studies on CBT effects in spider phobia (Schienle et al., 2007 and Schienle et al., 2009). We investigated whether those brain structures that have shown functional changes due to CBT (ACC, insula, amygdala, medial OFC) would also undergo structural changes.

3. Results 3.1. Self-report and behavioral approach test The patients had an average SPQ score of M = 21.91 (SD = 1.76) prior to CBT. This score was significantly reduced in the follow-up investigation (M = 4.36, SD = 2.06; t(11) = 20.48, p < .001). The SPQ score of the controls did not change from the first (M = 2.41, SD = 1.68) to the second assessment (M = 1.83, SD = 1.33, t(12) = 1.54, p = .15). The patients showed a significant increase in approach behavior over time (before CBT: M = 4.5 (SD = 1.8); follow-up session: M = 12 (0.0), t(12) = 12.1, p < .001), whereas the control subjects obtained a BAT score of 12 in both sessions. 3.2. VBM data The group comparison indicated that the patients were characterized by a greater GMV of the bilateral amygdala prior to CBT as well as in the 6-month follow-up investigation. The reversed contrast (controls > patients) revealed no statistically significant results. The within-group analyses for the selected ROIs detected a marginally significant reduction of left amygdala volume in the patient group (Table 1 and Fig. 1). Table 1. Gray matter volume differences between patients and controls and changes over time. Region H x y z Cluster size (voxel) T p(FWE) Before CBT: Patients > Controls Amygdala L −16 −3 −14 492 3.96 .007 Amygdala R 22 2 −17 468 3.46 .020 Six-month after CBT: Patients > Controls Amygdala L −16 −4 −15 485 3.73 .015 Amygdala R 22 −1 −12 579 5.37 .001 Before CBT > Six-month after CBT: Patients SMA L −3 −3 57 100 5.66 .022 Amygdala L −16 −3 −12 62 3.07 .088 Table options Full-size image (71 K) Fig. 1. Difference in amygdala volume between patients and controls (upper panel) and supplementary motor area volume in patients before and after cognitive behavior therapy (CBT). Figure options Additional exploratory analyses with further ROIs that are usually activated during visual symptom provocation in spider phobia (supplementary motor area (SMA), lateral OFC) showed that in the patient sample the SMA volume decreased over time (Table 1). The volume reduction of this ROI was correlated with the degree of symptom reduction (spider phobia questionnaire (SPQ) score prior CBT minus follow-up) as determined by means of simple regression (MNI coordinates: −3,30,64, t = 6.59, p(FWE) = .021). The group contrasts (patients < > controls) for SMA and OFC were nonsignificant prior as well as post CBT.