Positron emission tomography (PET) shows different effects of depression treatments on the brain, according to the results of a study published in the January issue of the Archives of General Psychiatry. Patients who recover after cognitive behavioral therapy (CBT) show a pattern of brain changes that is distinct from that of patients who respond to paroxetine.
"When treating clinical depression we know that one type of treatment doesn't fit all. Our imaging study shows that you can correct the depression network along a variety of pathways," senior author Helen Mayberg, MD, formerly from the University of Toronto in Ontario, Canada, and currently with Emory University in Atlanta, Georgia, says in a news release. "Antidepressant drugs change the chemical balance in the brain through effects at very specific target sites. CBT also changes brain activity; it's just tapping into a different component of the same depression circuit board."
By modifying attention and memory functions, affective bias, and maladaptive information processing, CBT teaches patients cognitive strategies to reduce automatic reactivity to negative thoughts. Unlike this "top-down" approach, which focuses on cortical brain areas and uses thought processes to modulate abnormal mood states, drug therapy is considered a "bottom-up" approach because it alters neurochemistry in the brain stem and limbic regions driving basic emotional and circadian behaviors.
Of 17 adults with clinical depression who were not taking antidepressant drugs and who were enrolled in this study, 14 underwent a full course of CBT consisting of 15 to 20 individualized outpatient sessions. Mean improvement in Hamilton Depression Rating Scale score was 6.7 ± 4. As an independent, post-hoc comparison group, 13 paroxetine-treated responders also had PET scans.
PET scanning before beginning CBT and after the full course of therapy revealed that CBT targets many of the same limbic and cortical regions affected by paroxetine therapy. However, metabolism decreased in the limbic area and increased in the cortical area with paroxetine, whereas CBT was associated with limbic system increases in the hippocampus and dorsal cingulate regions, and with decreases in the dorsolateral, ventrolateral and medial orbital frontal, inferior temporal, and parietal cortex.
Each treatment also showed changes in unique brain regions supporting the top-down, bottom-up mechanisms of action for CBT versus paroxetine. The investigators suggest that CBT allows patients to suppress the thinking paradigm associated with dwelling on negative thoughts and attitudes, which is reflected in decreased activity in cortical regions.
