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Individuals with major depressive disorder (MDD) are characterized by maladaptive responses to both positive and negative outcomes, which have been linked to localized abnormal activations in cortical and striatal brain regions. However, the exact neural circuitry implicated in such abnormalities remains largely unexplored.
In this study 26 unmedicated adults with MDD and 29 matched healthy controls (HCs) completed a monetary incentive delay task during functional magnetic resonance imaging (fMRI). Psychophysiological interaction (PPI) analyses probed group differences in connectivity separately in response to positive and negative outcomes (i.e. monetary gains and penalties).
Relative to HCs, MDD subjects displayed decreased connectivity between the caudate and dorsal anterior cingulate cortex (dACC) in response to monetary gains, yet increased connectivity between the caudate and a different, more rostral, dACC subregion in response to monetary penalties. Moreover, exploratory analyses of 14 MDD patients who completed a 12-week, double-blind, placebo-controlled clinical trial after the baseline fMRI scans indicated that a more normative pattern of cortico-striatal connectivity pre-treatment was associated with greater improvement in symptoms 12 weeks later.
These results identify the caudate as a region with dissociable incentive-dependent dACC connectivity abnormalities in MDD, and provide initial evidence that cortico-striatal circuitry may play a role in MDD treatment response. Given the role of cortico-striatal circuitry in encoding action–outcome contingencies, such dysregulated connectivity may relate to the prominent disruptions in goal-directed behavior that characterize MDD.
Objective/Introduction: We sought to characterize the impact of the 90-item Symptom Checklist (SCL-90) subscales for paranoid ideation (PI) and psychoticism (P) in patients with major depressive disorder (MDD), on acute anti-depressant response and on relapse prevention.
Methods: Subjects with Structured Clinical Interview for DSM Disorders-diagnosed non-psychotic MDD were recruited into a clinical trial of open-label fluoxetine 10–60 mg/day for 12 weeks, followed by double-blind randomization of responders (n=262) to fluoxetine continuation or placebo for 12 months. PI and P were assessed with the patient-rated SCL-90. The association of these symptoms with response to treatment was assessed by logistic regression.
Results: We found significant decreases in PI and P during acute treatment phase for fluoxetine responders and nonresponders, although only 10.3% and 7.5% of patients experienced a ≥50% reduction in PI and P scores, respectively. Neither PI nor P scores significantly predicted time to relapse. P scores predicted a lower response rate to treatment with fluoxetine.
Discussion: The results of the present study suggest that there is a significant relationship between the presence of psychoticism in patients with nonpsychotic MDD, and the likelihood of overall depressive symptom improvement following a trial of monotherapy with fluoxetine.
Conclusion: An increased burden of psychoticism in depressed subjects may confer poorer response to fluoxetine, but not increased risk of relapse among fluoxetine responders.
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