To cover this gap, Dunlop et al. investigated treatment-naive individuals who remitted after 12 weeks of cognitive behavioral therapy (CBT) or antidepressant medication (duloxetine or escitalopram). They compared the differences between the functional magnetic resonance imaging resting-state scans at baseline and the scans repeated after 12 weeks of receiving the randomized treatment. Independently of the remission after CBT or antidepressant medication, both groups displayed a reduction in the functional connectivity between the subcallosal cingulate cortex and a portion of the motor cortex. “Although we did not have a clinical correlate of motor change, there is an intuitive sense to this result, in that when people are no longer depressed, they frequently report it to be easier to initiate motor actions, such as getting out of bed or moving quicker from one place to another. This result raises the possibility that the subcallosal cingulate cortex, a key hub for processing negative affect, may have increased inhibitory input to the motor cortex when people are depressed and that is ameliorated when people are no longer depressed,” Boadie Dunlop, the first author of the paper, explains.
Next, only the CBT remitters exhibited increased connectivity within the executive control network and between the latter and the dorsal attention network. “This is a key finding because it is precisely through enhancing cognitive control and altering attention that CBT has been hypothesized to work,” Dunlop adds. In contrast to CBT, medications mostly reduced connectivity within and between networks. These results may ultimately help to identify individuals who do not need an ongoing exposure to medication, but who would instead benefit from CBT. Finally, the individuals who did not improve with either treatment failed to show many of the changes that occurred in the remitters. “This finding might enable early identification of patients who should be rapidly moved to non-first-line treatments, such as ketamine or transcranial magnetic stimulation, or perhaps an alternative evidence-based psychotherapy. Also, our study opens new avenues for distinguishing between state (present only when depressed) and trait (always present) features of depression,” Dunlop concludes.
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