Sex differences in plasma proteomic markers in late-life depression.

Previous studies have shown significant sex-specific differences in major depressive disorder (MDD) in multiple biological parameters. Most studies focused on young and middle-aged adults, and there is a paucity of information about sex-specific biological differences in older adults with depression (aka, late-life depression (LLD)). To address this gap, this study aimed to evaluate sex-specific biological abnormalities in a large group of individuals with LLD using an untargeted proteomic analysis. We quantified 344 plasma proteins using a multiplex assay in 430 individuals with LLD and 140 healthy comparisons (HC) (age range between 60 and 85 years old for both groups). Sixty-six signaling proteins were differentially expressed in LLD (both sexes). Thirty-three proteins were uniquely associated with LLD in females, while six proteins were uniquely associated with LLD in males. The main biological processes affected by these proteins in females were related to immunoinflammatory control. In contrast, despite the smaller number of associated proteins, males showed dysregulations in a broader range of biological pathways, including immune regulation pathways, cell cycle control, and metabolic control. Sex has a significant impact on biomarker changes in LLD. Despite some overlap in differentially expressed biomarkers, males and females show different patterns of biomarkers changes, and males with LLD exhibit abnormalities in a larger set of biological processes compared to females. Our findings can provide novel targets for sex-specific interventions in LLD.

Correction: Evaluating the Clinical Feasibility of an Artificial Intelligence-Powered, Web-Based Clinical Decision Support System for the Treatment of Depression in Adults: Longitudinal Feasibility Study.

[This corrects the article DOI: 10.2196/31862.].

CYP2D6 Phenotype Influences Pharmacokinetic Parameters of Venlafaxine: Results from a Population Pharmacokinetic Model in Older Adults with Depression.

In this study, we aimed to improve upon a published population pharmacokinetic (PK) model for venlafaxine (VEN) in the treatment of depression in older adults, then investigate whether CYP2D6 metabolizer status affected model-estimated PK parameters of VEN and its active metabolite O-desmethylvenlafaxine. The model included 325 participants from a clinical trial in which older adults with depression were treated with open-label VEN (maximum 300 mg/day) for 12 weeks and plasma levels of VEN and O-desmethylvenlafaxine were assessed at weeks 4 and 12. We fitted a nonlinear mixed-effect PK model using NONMEM to estimate PK parameters for VEN and O-desmethylvenlafaxine adjusted for CYP2D6 metabolizer status and age. At both lower doses (up to 150 mg/day) and higher doses (up to 300 mg/day), CYP2D6 metabolizers impacted PK model-estimated VEN clearance, VEN exposure, and active moiety (VEN + O-desmethylvenlafaxine) exposure. Specifically, compared with CYP2D6 normal metabolizers, (i) CYP2D6 ultra-rapid metabolizers had higher VEN clearance; (ii) CYP2D6 intermediate metabolizers had lower VEN clearance; (iii) CYP2D6 poor metabolizers had lower VEN clearance, higher VEN exposure, and higher active moiety exposure. Overall, our study showed that including a pharmacogenetic factor in a population PK model could increase model fit, and this improved model demonstrated how CYP2D6 metabolizer status affected VEN-related PK parameters, highlighting the importance of genetic factors in personalized medicine.

Psychosocial interventions to improve adherence in depressed and anxious older adults prescribed antidepressant pharmacotherapy: a scoping review.

Medication nonadherence in depressed and anxious older adults is prevalent and associated with non-response to antidepressant pharmacotherapy. Evidence-based options to improve medication adherence are limited in this population. To review the state of the literature on the types and efficacy of psychosocial interventions for improving antidepressant pharmacotherapy adherence in depressed and anxious older adults. We conducted a scoping review according to PRISMA-ScR guidelines. PubMed/Medline and article references starting in 1980 up to 28 February 2023 were reviewed. Of the 710 records screened, 4 psychosocial interventions were included in the review. All studies included depressed older adults, and none included anxious older adults. Samples included racial and ethnic minorities and were primarily women. The psychosocial interventions consisted mainly of psychoeducation with usual care as the control comparison. Measures of antidepressant adherence included self-reported adherence or pill counting. Three of the four randomized controlled trials improved medication adherence rates and reduced depression symptom burden. Effective interventions exist for improving antidepressant medication adherence in depressed older adults. Improved adherence can reduce depression symptom burden. The lack of interventions for anxious older adults highlights the need to develop and deliver interventions for anxious older adults prescribed antidepressant pharmacotherapy.

Life-Course Brain Health as a Determinant of Late-Life Mental Health: American Association for Geriatric Psychiatry Expert Panel Recommendations.

This position statement of the Expert Panel on Brain Health of the American Association for Geriatric Psychiatry (AAGP) emphasizes the critical role of life course brain health in shaping mental well-being during the later stages of life. Evidence posits that maintaining optimal brain health earlier in life is crucial for preventing and managing brain aging-related disorders such as dementia/cognitive decline, depression, stroke, and anxiety. We advocate for a holistic approach that integrates medical, psychological, and social frameworks with culturally tailored interventions across the lifespan to promote brain health and overall mental well-being in aging adults across all communities. Furthermore, our statement underscores the significance of prevention, early detection, and intervention in identifying cognitive decline, mood changes, and related mental illness. Action should also be taken to understand and address the needs of communities that traditionally have unequal access to preventive health information and services. By implementing culturally relevant and tailored evidence-based practices and advancing research in geriatric psychiatry, behavioral neurology, and geroscience, we can enhance the quality of life for older adults facing the unique challenges of aging. This position statement emphasizes the intrinsic link between brain health and mental health in aging, urging healthcare professionals, policymakers, and a broader society to prioritize comprehensive strategies that safeguard and promote brain health from birth through later years across all communities. The AAGP Expert Panel has the goal of launching further activities in the coming months and years.

Change in patient-centered outcomes of psychological well-being, sleep, and suicidality following treatment with intravenous ketamine for late-life treatment-resistant depression.

OBJECTIVE: To examine whether psychological well-being, sleep, and suicidality improved with treatment with intravenous (IV) ketamine for late-life treatment-resistant depression (TRD). METHODS: This is an analysis of secondary outcomes in an open-label late-life TRD study examining the safety, tolerability, and feasibility of IV ketamine infusions. In the acute phase, participants (N = 25) aged 60 years or older received twice-a-week IV ketamine for 4 weeks. Then, participants with Montgomery-Asberg Depression Rating Scale (MADRS) total score <10 or ≥ 30% reduction from baseline proceeded to the continuation phase, an additional four weeks of once-a-week IV ketamine. The secondary outcomes analyzed here are based on the National Institute of Health Toolbox Psychological Well-Being subscales for Positive Affect and General Life Satisfaction, the Pittsburgh Sleep Quality Index, and the Scale for Suicidal Ideation. RESULTS: Psychological well-being, sleep, and suicidality improved during the acute phase and those improvements were sustained during the continuation phase. Greater improvements in measures of psychological well-being and sleep were seen in participants who had greater improvements in MADRS scores and moved onto the continuation phase. All but one of the few participants with high suicidality at baseline improved; there were no cases of treatment-emergent suicidality. CONCLUSIONS: Psychological well-being, sleep, and suicidality improved in participants with late-life TRD who received IV ketamine for 8 weeks. A future larger and longer controlled trial is needed to confirm and extend these findings. REGISTRATION: ClinicalTrials.gov identifier: NCT04504175.

Exploratory genome-wide analyses of cortical inhibition, facilitation, and plasticity in late-life depression.

Late-life depression (LLD) is a heterogenous mood disorder influenced by genetic factors. Cortical physiological processes such as cortical inhibition, facilitation, and plasticity may be markers of illness that are more strongly associated with genetic factors than the clinical phenotype. Thus, exploring the relationship between genetic factors and these physiological processes may help to characterize the biological mechanisms underlying LLD and improve diagnosis and treatment selection. Transcranial magnetic stimulation (TMS) combined with electromyography was used to measure short interval intracortical inhibition (SICI), cortical silent period (CSP), intracortical facilitation (ICF), and paired associative stimulation (PAS) in 79 participants with LLD. We used exploratory genome-wide association and gene-based analyses to assess for genetic correlations of these TMS measures. MARK4 (which encodes microtubule affinity-regulating kinase 4) and PPP1R37 (which encodes protein phosphatase 1 regulatory subunit 37) showed genome-wide significant association with SICI. EGFLAM (which encodes EGF-like fibronectin type III and laminin G domain) showed genome-wide significant association with CSP. No genes met genome-wide significant association with ICF or PAS. We observed genetic influences on cortical inhibition in older adults with LLD. Replication with larger sample sizes, exploration of clinical phenotype subgroups, and functional analysis of relevant genotypes is warranted to better characterize genetic influences on cortical physiology in LLD. This work is needed to determine whether cortical inhibition may serve as a biomarker to improve diagnostic precision and guide treatment selection in LLD.

Dynamic Feedback Between Antidepressant Placebo Expectancies and Mood.

Importance: Despite high antidepressant placebo response rates, the mechanisms underlying the persistence of antidepressant placebo effects are still poorly understood. Objective: To investigate the neurobehavioral mechanisms underlying the evolution of antidepressant placebo effects using a reinforcement learning (RL) framework. Design, Setting, and Participants: In this acute within-patient cross-sectional study of antidepressant placebos, patients aged 18 to 55 years not receiving medication for major depressive disorder (MDD) were recruited at the University of Pittsburgh between February 21, 2017, to March 1, 2021. Interventions: The antidepressant placebo functional magnetic resonance imaging task manipulates placebo-associated expectancies using visually cued fast-acting antidepressant infusions and controls their reinforcement with sham visual neurofeedback while assessing expected and experienced mood improvement. Main Outcomes and Measures: The trial-by-trial evolution of expectancies and mood was examined using multilevel modeling and RL, relating model-predicted signals to spatiotemporal dynamics of blood oxygenation level-dependent (BOLD) response. Results: A bayesian RL model comparison in 60 individuals (mean [SE] age, 24.5 [0.8] years; 51 females [85%]) with MDD revealed that antidepressant placebo trial-wise expectancies were updated by composite learning signals multiplexing sensory evidence (neurofeedback) and trial-wise mood (bayesian omnibus risk <0.001; exceedance probability = 97%). Placebo expectancy, neurofeedback manipulations, and composite learning signals modulated the visual cortex and dorsal attention network (threshold-free cluster enhancement [TFCE] = 1 - P >.95). As participants anticipated antidepressant infusions, learned placebo expectancies modulated the salience network (SN, TFCE = 1 - P >.95), positively scaling with depression severity. Conclusions and Relevance: Results of this cross-sectional study suggest that on a timescale of minutes, antidepressant placebo effects were maintained by positive feedback loops between expectancies and mood improvement. During learning, representations of placebos and their perceived effects were enhanced in primary and secondary sensory cortices. Latent learned placebo expectancies were encoded in the SN.

Antidepressant Augmentation versus Switch in Treatment-Resistant Geriatric Depression.

BACKGROUND: The benefits and risks of augmenting or switching antidepressants in older adults with treatment-resistant depression have not been extensively studied. METHODS: We conducted a two-step, open-label trial involving adults 60 years of age or older with treatment-resistant depression. In step 1, patients were randomly assigned in a 1:1:1 ratio to augmentation of existing antidepressant medication with aripiprazole, augmentation with bupropion, or a switch from existing antidepressant medication to bupropion. Patients who did not benefit from or were ineligible for step 1 were randomly assigned in step 2 in a 1:1 ratio to augmentation with lithium or a switch to nortriptyline. Each step lasted approximately 10 weeks. The primary outcome was the change from baseline in psychological well-being, assessed with the National Institutes of Health Toolbox Positive Affect and General Life Satisfaction subscales (population mean, 50; higher scores indicate greater well-being). A secondary outcome was remission of depression. RESULTS: In step 1, a total of 619 patients were enrolled; 211 were assigned to aripiprazole augmentation, 206 to bupropion augmentation, and 202 to a switch to bupropion. Well-being scores improved by 4.83 points, 4.33 points, and 2.04 points, respectively. The difference between the aripiprazole-augmentation group and the switch-to-bupropion group was 2.79 points (95% CI, 0.56 to 5.02; P = 0.014, with a prespecified threshold P value of 0.017); the between-group differences were not significant for aripiprazole augmentation versus bupropion augmentation or for bupropion augmentation versus a switch to bupropion. Remission occurred in 28.9% of patients in the aripiprazole-augmentation group, 28.2% in the bupropion-augmentation group, and 19.3% in the switch-to-bupropion group. The rate of falls was highest with bupropion augmentation. In step 2, a total of 248 patients were enrolled; 127 were assigned to lithium augmentation and 121 to a switch to nortriptyline. Well-being scores improved by 3.17 points and 2.18 points, respectively (difference, 0.99; 95% CI, -1.92 to 3.91). Remission occurred in 18.9% of patients in the lithium-augmentation group and 21.5% in the switch-to-nortriptyline group; rates of falling were similar in the two groups. CONCLUSIONS: In older adults with treatment-resistant depression, augmentation of existing antidepressants with aripiprazole improved well-being significantly more over 10 weeks than a switch to bupropion and was associated with a numerically higher incidence of remission. Among patients in whom augmentation or a switch to bupropion failed, changes in well-being and the occurrence of remission with lithium augmentation or a switch to nortriptyline were similar. (Funded by the Patient-Centered Outcomes Research Institute; OPTIMUM ClinicalTrials.gov number, NCT02960763.).

Association between lean muscle mass and treatment-resistant late-life depression in the IRL-GRey randomized controlled trial.

OBJECTIVE: To investigate the relationship between lean muscle mass and treatment response in treatment-resistant late-life depression (TR-LLD). We hypothesized that lower lean muscle mass would be associated with older age, higher physical comorbidities, higher depressive symptom severity, and poorer treatment response. DESIGN: Secondary analysis of a randomized, placebo-controlled trial. SETTING: Three academic hospitals in the United States and Canada. PARTICIPANTS: Adults aged 60+ years with major depressive disorder who did not remit following open treatment with venlafaxine extended-release (XR) (n = 178). MEASUREMENTS: We estimated lean muscle mass using dual-energy X-ray absorptiometry (DEXA) scans prior to and following randomized treatment with aripiprazole or placebo added to venlafaxine XR. Multivariate regressions estimated influence of demographic and clinical factors on baseline lean muscle mass, and whether baseline lean muscle mass was associated with treatment response, adjusted for treatment arm. RESULTS: Low lean muscle mass was present in 22 (12.4%) participants. Older age and female sex, but not depressive symptom severity, were independently associated with lower lean muscle mass at baseline. Marital status, baseline depressive symptom severity, and treatment group were associated with improvement of depressive symptoms in the randomized treatment phase. Baseline lean muscle mass was not associated with improvement, regardless of treatment group. CONCLUSION: As expected, older age and female sex were associated with lower lean muscle mass in TR-LLD. However, contrary to prior results in LLD, lean muscle mass was not associated with depression severity or outcome. This suggests that aripiprazole augmentation may be useful for TR-LLD, even in the presence of anomalous body composition.clinicaltrials.gov Identifier: NCT00892047.

Sleep continuity, timing, quality, and disorder are associated with suicidal ideation and suicide attempts among college students.

Objective: To evaluate sleep continuity, timing, quality, and disorder in relation to suicidal ideation and attempts among college students. Participants: Eight hundred eighty-five undergraduates aged 18-25 in the southwestern United States. Methods: Participants completed questionnaires on sleep, suicide risk, mental health, and substance use. Differences in sleep variables were compared by lifetime and recent suicidal ideation and suicide attempts using covariate-adjusted and stepwise regression models. Results: A total of 363 (41.0%) individuals reported lifetime suicidal ideation, of whom 172 (47.4%) reported suicidal ideation in the last 3 months and 97 (26.7%) had attempted suicide in their lifetime. Sleep disturbances were prevalent among those with lifetime suicidal ideation or a lifetime suicide attempt. Insomnia was identified as the best predictor of recent suicidal ideation, but this relationship did not survive adjustment for covariates. Conclusions: Sleep continuity, quality, and sleep disorders are broadly associated with suicidal thoughts and behaviors among college students.

Back Pain Consortium (BACPAC): Protocol and Pilot Study Results for a Randomized Comparative-Effectiveness Trial of Antidepressants, Fear Avoidance Rehabilitation, or the Combination for Chronic Low Back Pain and Comorbid High Negative Affect.

OBJECTIVE: Patients with chronic low back pain (CLBP) and comorbid depression or anxiety disorders are highly prevalent. Negative affect (NA) refers to a combination of negative thoughts, emotions, and behaviors. Patients with CLBP with high NA have greater pain, worse treatment outcomes, and greater prescription opioid misuse. We present the protocol for SYNNAPTIC (SYNergizing Negative Affect & Pain Treatment In Chronic pain). DESIGN: A randomized comparative-effectiveness study of antidepressants, fear-avoidance rehabilitation, or their combination in 300 patients with CLBP with high NA. In the antidepressant- or rehabilitation-only arms, SYNNAPTIC includes an adaptive design of re-randomization after 4 months for nonresponders. SETTING: A multisite trial conducted in routine pain clinical treatment settings: pain clinics and physical and occupational therapy treatment centers. METHODS: Inclusion criteria include CLBP with elevated depression and anxiety symptoms. Antidepressant and rehabilitation treatments follow validated and effective protocols for musculoskeletal pain in patients with high NA. Power and sample size are based on superior outcomes of combination therapy with these same treatments in a 71-subject 4-arm pilot randomized controlled trial. CONCLUSIONS: SYNNAPTIC addresses the lack of evidence-based protocols for the treatment of the vulnerable subgroup of patients with CLBP and high NA. We hypothesize that combination therapy of antidepressants plus fear-avoidance rehabilitation will be more effective than each treatment alone. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT04747314.

Intravenous Ketamine for Late-Life Treatment-Resistant Depression: A Pilot Study of Tolerability, Safety, Clinical Benefits, and Effect on Cognition.

OBJECTIVE: Evidence-based treatment options for late-life treatment-resistant depression (TRD) are limited. Ketamine is a promising treatment for TRD; however, there is a paucity of data on its safety and efficacy in older adults. METHODS: In this pilot clinical trial, 25 adults aged ≥60 years with TRD received IV ketamine openly twice a week for 4 weeks; partial responders at the end of this acute phase were eligible to receive weekly infusions for 4 more weeks in a continuation phase. Acceptability, tolerability, and safety, including adverse and serious adverse events (AEs and SAEs), blood pressure changes, dissociation, craving, in addition to rates of depression response and remission were evaluated. The NIH Toolbox Cognitive Battery was used to assess specific measures of executive function (EF) and overall fluid cognition. RESULTS: Completion rates were 88% for the acute phase and 100% for the continuation phase. No AEs resulted in participant discontinuation, and there were no SAEs. Treatment-emergent elevation of blood pressure, dissociation, and craving were transient and did not result in any participant discontinuation. Depressive symptoms improved significantly and 48% of participants responded. During the acute phase, the EF measures and the fluid cognition composite score improved (Cohen's d = 0.61), and these improvements were sustained in the continuation phase. CONCLUSION: This pilot study suggests that repeated IV ketamine infusions are well-tolerated and are associated with improvement in depression and EF in older adults with TRD. These promising findings need to be confirmed and extended in a larger randomized controlled trial.

A digital health intervention to stabilize the 24-hour rhythm of sleep, meals, and physical activity for reducing depression among older bereaved spouses: Protocol for a randomized controlled trial.

BACKGROUND: Despite the high prevalence of depression and disruption to 24-h sleep-wake routines following the death of a spouse in late-life, no bereavement interventions have been developed to re-entrain a regular sleep-wake routine among older widow(er)s. We describe the rationale and methodology of the NIH-funded WELL Study (Widowed Elders' Lifestyle after Loss), a randomized controlled trial (RCT) comparing the efficacy of a digital health intervention (DHI) to enhanced usual care (EUC) arm for reducing depression symptoms in older spousally-bereaved adults. METHODS: We will randomize approximately 200 recently bereaved (<12 months) adults aged 60+ years to one of two 12-week interventions: digital monitoring of the timing and regularity of sleep, meals, and physical activity plus weekly motivational health coaching; or enhanced usual care consisting of weekly telephone calls and similar assessment schedules. Participants will complete self-report and clinical assessments at baseline, post-intervention, and 3-, 6-, and 12-months post-intervention, and objective actigraphic assessments of their 24-h rest-activity rhythm (RAR) at baseline and 1-, 2-, and 3-months during the intervention. The primary outcome is change in depression symptoms burden (using the Hamilton Rating Scale for Depression) from pre- to post-intervention and over 12 months of follow-up. DISCUSSION: WELL Study findings will inform the development of widely generalizable and scalable technology-based interventions to support bereaved spouses in community-based settings. Clinical http://Trials.gov Identifier: NCT04016896.

Differential Placebo Responses for Pharmacotherapy and Neurostimulation in Late-Life Depression.

BACKGROUND: The magnitude of the placebo response depends on both the modality used as the "placebo" and the intervention with which it is compared, both of which can complicate the interpretation of randomized controlled trials (RCTs) for depression in late life. Given that neurostimulation and pharmacotherapy are among the most common interventions studied for late-life depression, comparing the relative placebo responses in studies of these interventions can aid interpretation of relative effect sizes. MATERIALS AND METHODS: We analyzed data from two RCTs of adults aged ≥60 years in an episode of treatment-resistant major depression, one comparing aripiprazole and matching placebo pills and the other comparing deep repetitive transcranial magnetic stimulation (rTMS) and sham rTMS. In both RCTs, depression was assessed using the 17-item Hamilton Depression Rating Scale (HDRS-17). The primary comparison occurred after four weeks using analysis of covariance (ANCOVA) of HDRS-17 scores in participants who received placebo pills or sham rTMS. Relevant covariates included years of education, duration of depressive episode, and baseline HDRS-17 score. RESULTS: Accounting for covariates, there was a larger reduction of HDRS-17 after four weeks in the sham rTMS group (estimated marginal mean ± SE: -5.90 ± 1.45; 95% CI: [-8.82, 2.98]) than in the placebo pills group (-1.07 ± 1.45; [-3.98, 1.85]). There were no significant differences between these groups in the binary outcome analysis of response and remission rates at four weeks or any outcome at trial end point comparison. CONCLUSIONS: Sham rTMS may have a larger placebo response than placebo pills early in the treatment of older adults with treatment-resistant depression. Differential placebo responses should be considered in both the interpretation and design of RCTs.

Late-Life Depression is Associated With Increased Levels of GDF-15, a Pro-Aging Mitokine.

OBJECTIVE: In older adults, major depressive disorder (MDD) is associated with accelerated physiological and cognitive aging, generating interest in uncovering biological pathways that may be targetable by interventions. Growth differentiation factor-15 (GDF-15) plays a significant role in biological aging via multiple biological pathways relevant to age and age-related diseases. Elevated levels of GDF-15 correlate with increasing chronological age, decreased telomerase activity, and increased mortality risk in older adults. We sought to evaluate the circulating levels of GDF-15 in older adults with MDD and its association with depression severity, physical comorbidity burden, age of onset of first depressive episode, and cognitive performance. DESIGN: This study assayed circulating levels of GDF-15 in 393 older adults (mean ± SD age 70 ± 6.6 years, male:female ratio 1:1.54), 308 with MDD and 85 non-depressed comparison individuals. RESULTS: After adjusting for confounding variables, depressed older adults had significantly higher GDF-15 serum levels (640.1 ± 501.5 ng/mL) than comparison individuals (431.90 ± 223.35 ng/mL) (t=3.75, d.f.= 391, p=0.0002). Among depressed individuals, those with high GDF-15 had higher levels of comorbid physical illness, lower executive cognitive functioning, and higher likelihood of having late-onset depression. CONCLUSION: Our results suggest that depression in late life is associated with GDF-15, a marker of amplified age-related biological changes. GDF-15 is a novel and potentially targetable biological pathway between depression and accelerated aging, including cognitive aging.

Low-Dose Augmentation With Buprenorphine for Treatment-Resistant Depression: A Multisite Randomized Controlled Trial With Multimodal Assessment of Target Engagement.

Background: The experimental therapeutics approach that combines a placebo-controlled clinical trial with translational neuroscience methods can provide a better understanding of both the clinical and physiological effects of pharmacotherapy. We aimed to test the efficacy and tolerability of low-dose augmentation with buprenorphine (BPN) for treatment-resistant depression, combined with multimodal assessment of target engagement. Methods: In this multisite randomized clinical trial, 85 participants ≥50 years of age with a major depressive episode that had not responded to venlafaxine extended release were randomized to augmentation with BPN or placebo for 8 weeks. The primary outcome measure was the Montgomery-Åsberg Depression Rating Scale. In addition, three linked experiments were conducted to test target engagement: 1) functional magnetic resonance imaging using the monetary incentive delay task, 2) brain positron emission tomography of healthy participants using a novel kappa opioid receptor antagonist tracer [11C]LY2795050, and 3) transcranial magnetic stimulation measure of cortical transmission after daily BPN administration. Results: The mean ± SD dosage of BPN was 0.59 ± 0.33 mg/day. There were no significant differences between the BPN and placebo groups in Montgomery-Åsberg Depression Rating Scale changes over time or adverse effects. BPN administration had minimal effects on functional magnetic resonance imaging blood oxygen level-dependent responses in regions involved in reward anticipation and response, no significant displacement of kappa opioid receptor radioligand in positron emission tomography imaging, and no significant changes in transcranial magnetic stimulation measures of inhibitory and excitatory cortical transmission. Conclusions: Our findings suggest a lack of clinical effect of low-dose BPN augmentation and lack of target engagement with this dosage and physiological probes.