RESUMEN
The neurobiological mechanisms underlying the placebo phenomenon in patients with major depressive disorder (MDD) remain largely unknown. The progressive rise in rates of placebo responses within clinical trials over the past two decades may impede the detection of a true signal and thus present a major obstacle in new treatment development. Understanding the mechanisms would have several important implications, including (1) identifying biomarkers of placebo responders (thereby identifying those individuals who could benefit therapeutically from such interventions), (2) opening new avenues for manipulating such mechanisms to maximize symptom reduction, and (3) refining treatments with approaches that decrease (in clinical trials) or increase (in clinical practice) the placebo response. Here we investigated the research question: is the dopaminergic system one of the neurobiological underpinnings of the placebo response within MDD? Inspired by preclinical and clinical findings that have implicated dopamine in the occurrence, prediction, and expectation of reward, we hypothesized that dopaminergic activity in the mesolimbic system is a critical mediator of placebo response in MDD. To test this hypothesis, we designed a double-blind, placebo-controlled, sequential parallel comparison design clinical trial aimed at maximizing placebo antidepressant response. We integrated behavioral, imaging, and hemodynamic probes of mesocorticolimbic dopaminergic pathways within the context of manipulations of psychological constructs previously linked to placebo responses (e.g., expectation of improvement). The aim of this manuscript is to present the rationale of the study design and to demonstrate how a cross-modal methodology may be utilized to investigate the role of reward circuitry in placebo response in MDD.
RESUMEN
The Probabilistic Reward Task (PRT) is widely used to investigate the impact of Major Depressive Disorder (MDD) on reinforcement learning (RL), and recent studies have used it to provide insight into decision-making mechanisms affected by MDD. The current project used PRT data from unmedicated, treatment-seeking adults with MDD to extend these efforts by: (1) providing a more detailed analysis of standard PRT metrics-response bias and discriminability-to better understand how the task is performed; (2) analyzing the data with two computational models and providing psychometric analyses of both; and (3) determining whether response bias, discriminability, or model parameters predicted responses to treatment with placebo or the atypical antidepressant bupropion. Analysis of standard metrics replicated recent work by demonstrating a dependency between response bias and response time (RT), and by showing that reward totals in the PRT are governed by discriminability. Behavior was well-captured by the Hierarchical Drift Diffusion Model (HDDM), which models decision-making processes; the HDDM showed excellent internal consistency and acceptable retest reliability. A separate "belief" model reproduced the evolution of response bias over time better than the HDDM, but its psychometric properties were weaker. Finally, the predictive utility of the PRT was limited by small samples; nevertheless, depressed adults who responded to bupropion showed larger pre-treatment starting point biases in the HDDM than non-responders, indicating greater sensitivity to the PRT's asymmetric reinforcement contingencies. Together, these findings enhance our understanding of reward and decision-making mechanisms that are implicated in MDD and probed by the PRT.
RESUMEN
OBJECTIVE: The current study examines the relationships between change in depressive symptoms and locus of control orientations among college students during the COVID-19 pandemic. Participants: A sample of 341 undergraduate students were recruited from a large Midwestern United States university.Methods: Participants completed an online cross-sectional survey with self-report measures of current depressive symptoms, retrospective pre-pandemic depressive symptoms, and locus of control.Results: Depressive symptoms changed significantly during the COVID-19 pandemic (t(340) = 7.49, p < 0.01). Pre-pandemic depressive symptoms predicted symptom change with the greatest changes among students who had fewer pre-pandemic symptoms (b = -0.58, p < 0.01) and higher external locus of control orientation (b = 0.24, p < 0.01).Conclusions: An increased presence of mental health resources is needed on college campuses and external locus of control should be targeted through clinical intervention as a risk factor for adverse depressive responses to stressors among college students.
RESUMEN
OBJECTIVE: Children with some chronic health conditions experience family functioning difficulties. However, research examining family functioning in youth with functional gastrointestinal disorders (FGIDs) has produced mixed results. Therefore, the current review critically synthesized the literature on family functioning among youth with FGIDs. METHODS: A systematic search using pediatric, family functioning, and FGID search terms was conducted in PubMed, PsycInfo, and ProQuest. Out of the 586 articles initially identified, 17 studies met inclusion criteria. Studies were included if they presented original research in English, assessed family functioning, and the study sample consisted of children (0-18 years) diagnosed with a FGID. Quality assessment ratings were conducted for each included study based on a previously developed scientific merit 3-point rating system. RESULTS: The majority of studies (n = 13) examined family functioning between youth with FGIDs and comparison groups. The remaining studies explored associations between family functioning and study variables (e.g., child psychosocial functioning and sociodemographic factors) and examined family functioning clusters among children with FGIDs. In general, children with FGIDs demonstrated poorer family functioning compared to healthy counterparts. Findings also suggested that child psychosocial functioning, disease characteristics, and sociodemographic factors were related to family functioning among youth with FGIDs. The average quality of studies was moderate (M = 2.3). CONCLUSIONS: Maintaining healthy family functioning appears to be challenging for some families of children with FGIDs. Future research should explore the directionality of the relationship between family functioning and child physical and psychosocial outcomes to advance the understanding and treatment of pediatric FGIDs.