Cognitive behavioral therapy for phobias reduces cerebral blood flow to certain brain areas

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Cognitive behavioral therapy (CBT) for a phobia can reduce cerebral blood flow, according to a recent study published this September in Brain and Behavior. The study is the first to use arterial spin labeling to measure cerebral blood flow changes in phobia-associated regions following CBT.

A specific phobia, such as spider phobia, is an anxiety disorder characterized by rapid, exaggerated, and persistent fear responses to a phobic situation or object, which interferes with daily functioning or causes significant distress.

A large amount of research has provided evidence that CBT is the method of choice for the treatment of specific phobias, with therapy often using exposure and cognitive restructuring as part of the treatment process. Brain imaging studies have shown that CBT is able to change brain activation in response to threatening stimuli in both emotion-generating and modulatory regions.

Generally this research has used conventional blood oxygenation level-dependent functional magnetic resonance imaging (fMRI). However, arterial spin labelling, a non-invasive fMRI method that traces water molecules in arteries, can measure cerebral blood flow (the blood supply to the brain in a given period of time) more accurately. The method is more accurate particularly because it is sensitive to slow variations in brain activity.

The study, led by Leila Soravia of the University of Bern, explored the resting state cerebral blood flow measured by arterial spin labelling, before and after CBT. Eight female patients with spider phobia were scanned before and 1 month after an exposure-based group therapy for spider phobia. For the scan, patients were shown pictures of spiders and their anticipatory anxiety and post-processing of phobia-relevant information was measured.

The results revealed that CBT significantly reduced spider phobic symptoms in all patients. Symptom reduction during anticipatory anxiety was accompanied by reduced cerebral blood flow in the parahippocampal gyrus, ventral anterior thalamus, Brodmann area 8, and the anterior cingulate cortex. During post-processing of phobia-relevant information, patients showed reduced cerebral blood blow in the insula, components of the motor cortex, and areas associated with language functions.

The researchers concluded, “This is the first ASL (arterial spin labelling) study to replicate results from different fMRI studies, and show that successful CBT for a phobia can change brain activity in the MTL (medial temporal lobe) and insula during the resting state. ASL also enables absolute quantification of CBF (cerebral blood flow) changes in the corresponding phobia-associated regions.”

The findings suggest that ASL may be a suitable method for monitoring and evaluating whether different psychotherapy or pharmacotherapy treatments are effective.