Cognitive neuropsychological theory of antidepressant action: a modern-day approach to depression and its treatment

Beyond the serotonin deficit hypothesis: communicating a neuroplasticity framework of major depressive disorder

The serotonin deficit hypothesis explanation for major depressive disorder (MDD) has persisted among clinicians and the general public alike despite insufficient supporting evidence. To combat rising mental health crises and eroding public trust in science and medicine, researchers and clinicians must be able to communicate to patients and the public an updated framework of MDD: one that is (1) accessible to a general audience, (2) accurately integrates current evidence about the efficacy of conventional serotonergic antidepressants with broader and deeper understandings of pathophysiology and treatment, and (3) capable of accommodating new evidence. In this article, we summarize a framework for the pathophysiology and treatment of MDD that is informed by clinical and preclinical research in psychiatry and neuroscience. First, we discuss how MDD can be understood as inflexibility in cognitive and emotional brain circuits that involves a persistent negativity bias. Second, we discuss how effective treatments for MDD enhance mechanisms of neuroplasticity-including via serotonergic interventions-to restore synaptic, network, and behavioral function in ways that facilitate adaptive cognitive and emotional processing. These treatments include typical monoaminergic antidepressants, novel antidepressants like ketamine and psychedelics, and psychotherapy and neuromodulation techniques. At the end of the article, we discuss this framework from the perspective of effective science communication and provide useful language and metaphors for researchers, clinicians, and other professionals discussing MDD with a general or patient audience.

Amygdala Reactivity, Antidepressant Discontinuation, and Relapse

Importance

Antidepressant discontinuation substantially increases the risk of a depression relapse, but the neurobiological mechanisms through which this happens are not known. Amygdala reactivity to negative information is a marker of negative affective processes in depression that is reduced by antidepressant medication, but it is unknown whether amygdala reactivity is sensitive to antidepressant discontinuation or whether any change is related to the risk of relapse after antidepressant discontinuation.

Objective

To investigate whether amygdala reactivity to negative facial emotions changes with antidepressant discontinuation and is associated with subsequent relapse.

Design, Setting, and Participants

The Antidepressiva Absetzstudie (AIDA) study was a longitudinal, observational study in which adult patients with remitted major depressive disorder (MDD) and currently taking antidepressants underwent 2 task-based functional magnetic resonance imaging (fMRI) measurements of amygdala reactivity. Patients were randomized to discontinuing antidepressants either before or after the second fMRI measurement. Relapse was monitored over a 6-month follow-up period. Study recruitment took place from June 2015 to January 2018. Data were collected between July 1, 2015, and January 31, 2019, and statistical analyses were conducted between June 2021 and December 2023. The study took place in a university setting in Zurich, Switzerland, and Berlin, Germany. Of 123 recruited patients, 83 were included in analyses. Of 66 recruited healthy control individuals matched for age, sex, and education, 53 were included in analyses.

Exposure

Discontinuation of antidepressant medication.

Outcomes

Task-based fMRI measurement of amygdala reactivity and MDD relapse within 6 months after discontinuation.

Results

Among patients with MDD, the mean (SD) age was 35.42 (11.41) years, and 62 (75%) were women. Among control individuals, the mean (SD) age was 33.57 (10.70) years, and 37 (70%) were women. Amygdala reactivity of patients with remitted MDD and taking medication did not initially differ from that of control individuals (t125.136 = 0.33; P = .74). An increase in amygdala reactivity after antidepressant discontinuation was associated with depression relapse (3-way interaction between group [12W (waited) vs 1W2 (discontinued)], time point [MA1 (first scan) vs MA2 (second scan)], and relapse: β, 18.9; 95% CI, 0.8-37.1; P = .04). Amygdala reactivity change was associated with shorter times to relapse (hazard ratio, 1.05; 95% CI, 1.01-1.09; P = .01) and predictive of relapse (leave-one-out cross-validation balanced accuracy, 67%; 95% posterior predictive interval, 53-80; P = .02).

Conclusions and Relevance

An increase in amygdala reactivity was associated with risk of relapse after antidepressant discontinuation and may represent a functional neuroimaging marker that could inform clinical decisions around antidepressant discontinuation.

Breakthroughs and challenges for generating brain network-based biomarkers of treatment response in depression

Treatment outcomes widely vary for individuals diagnosed with major depressive disorder, implicating a need for deeper understanding of the biological mechanisms conferring a greater likelihood of response to a particular treatment. Our improved understanding of intrinsic brain networks underlying depression psychopathology via magnetic resonance imaging and other neuroimaging modalities has helped reveal novel and potentially clinically meaningful biological markers of response. And while we have made considerable progress in identifying such biomarkers over the last decade, particularly with larger, multisite trials, there are significant methodological and practical obstacles that need to be overcome to translate these markers into the clinic. The aim of this review is to review current literature on brain network structural and functional biomarkers of treatment response or selection in depression, with a specific focus on recent large, multisite trials reporting predictive accuracy of candidate biomarkers. Regarding pharmaco- and psychotherapy, we discuss candidate biomarkers, reporting that while we have identified candidate biomarkers of response to a single intervention, we need more trials that distinguish biomarkers between first-line treatments. Further, we discuss the ways prognostic neuroimaging may help to improve treatment outcomes to neuromodulation-based therapies, such as transcranial magnetic stimulation and deep brain stimulation. Lastly, we highlight obstacles and technical developments that may help to address the knowledge gaps in this area of research. Ultimately, integrating neuroimaging-derived biomarkers into clinical practice holds promise for enhancing treatment outcomes and advancing precision psychiatry strategies for depression management. By elucidating the neural predictors of treatment response and selection, we can move towards more individualized and effective depression interventions, ultimately improving patient outcomes and quality of life.

General and anxiety-linked influences of acute serotonin reuptake inhibition on neural responses associated with attended visceral sensation

Ordinary sensations from inside the body are important causes and consequences of our affective states and behaviour, yet the roles of neurotransmitters in interoceptive processing have been unclear. With a within-subjects design, this experiment tested the impacts of acute increases of endogenous extracellular serotonin on the neural processing of attended internal sensations and the links of these effects to anxiety using a selective serotonin reuptake inhibitor (SSRI) (20 mg CITALOPRAM) and a PLACEBO. Twenty-one healthy volunteers (fourteen female, mean age 23.9) completed the Visceral Interoceptive Attention (VIA) task while undergoing functional magnetic resonance imaging (fMRI) with each treatment. The VIA task required focused attention on the heart, stomach, or visual sensation. The relative neural interoceptive responses to heart sensation [heart minus visual attention] (heart-IR) and stomach sensation [stomach minus visual attention] (stomach-IR) were compared between treatments. Visual attention subtraction controlled for the general effects of CITALOPRAM on sensory processing. CITALOPRAM was associated with lower interoceptive processing in viscerosensory (the stomach-IR of bilateral posterior insular cortex) and integrative/affective (the stomach-IR and heart-IR of bilateral amygdala) components of interoceptive neural pathways. In anterior insular cortex, CITALOPRAM reductions of heart-IR depended on anxiety levels, removing a previously known association between anxiety and the region's response to attended heart sensation observed with PLACEBO. Preliminary post hoc analysis indicated that CITALOPRAM effects on the stomach-IR of the amygdalae corresponded to acute anxiety changes. This direct evidence of general and anxiety-linked serotonergic influence on neural interoceptive processes advances our understanding of interoception, its regulation, and anxiety.

Predictive modeling of antidepressant efficacy based on cognitive neuropsychological theory

BACKGROUND

We aimed to develop a clinical predictive model based on the cognitive neuropsychological (CNP) theory and machine-learning to examine SSRI efficacy in the treatment of MDD.

METHODS

Baseline assessments including clinical symptoms (HAMD, HAMA, BDI, and TEPS scores), negative biases (NEO-PI-R-N and NCPBQ scores), sociodemographic characteristics (social support and SES), and a 5-min eye-opening resting-state EEG were completed by 69 participants with first-episode major depressive disorder (MDD) and 36 healthy controls. The clinical symptoms and negative bias were again assessed after an 8-week treatment of depression with selective serotonin reuptake inhibitors (SSRIs). A multi-modality machine-learning model was developed to predict the effectiveness of SSRI antidepressants.

RESULTS

At baseline, we observed significant differences between MDD patients and healthy controls in terms of social support, clinical symptoms, and negative bias characteristics (p < 0.001). A negative association was found (p < 0.05) between neuroticism and alpha asymmetry in both the central and central-parietal areas, as well as between negative cognitive processing bias and alpha asymmetry in the parietal region. Compared to responders, non-responders exhibited less negative cognitive processing bias and greater alpha asymmetry in both central and central-parietal regions. Importantly, we developed a multi-modality machine-learning model with 83 % specificity using the above salient features.

CONCLUSIONS

Research results support the CNP theory of depression treatment. To some extent, the multimodal clinical model constructed based on the CNP theory effectively predicted the efficacy of this treatment in this population.

LIMITATIONS

Small sample and only focus on the mechanisms of delayed-onset SSRI treatment.

Acute neural effects of the mood stabiliser lamotrigine on emotional processing in healthy volunteers: a randomised control trial

Lamotrigine is an effective mood stabiliser, largely used for the management and prevention of depression in bipolar disorder. The neuropsychological mechanisms by which lamotrigine acts to relieve symptoms as well as its neural effects on emotional processing remain unclear. The primary objective of this current study was to investigate the impact of an acute dose of lamotrigine on the neural response to a well-characterised fMRI task probing implicit emotional processing relevant to negative bias. 31 healthy participants were administered either a single dose of lamotrigine (300 mg, n = 14) or placebo (n = 17) in a randomized, double-blind design. Inside the 3 T MRI scanner, participants completed a covert emotional faces gender discrimination task. Brain activations showing significant group differences were identified using voxel-wise general linear model (GLM) nonparametric permutation testing, with threshold free cluster enhancement (TFCE) and a family wise error (FWE)-corrected cluster significance threshold of p < 0.05. Participants receiving lamotrigine were more accurate at identifying the gender of fearful (but not happy or angry) faces. A network of regions associated with emotional processing, including amygdala, insula, and the anterior cingulate cortex (ACC), was significantly less activated in the lamotrigine group compared to the placebo group across emotional facial expressions. A single dose of lamotrigine reduced activation in limbic areas in response to faces with both positive and negative expressions, suggesting a valence-independent effect. However, at a behavioural level lamotrigine appeared to reduce the distracting effect of fear on face discrimination. Such effects may be relevant to the mood stabilisation effects of lamotrigine.

Rationale and design of a double-blinded, randomized placebo-controlled trial of 40 Hz light neurostimulation therapy for depression (FELIX)

BACKGROUND

Major depressive disorder (MDD) is a debilitating condition that affects more than 300 million people worldwide. Current treatments are based on a trial-and-error approach, and reliable biomarkers are needed for more informed and personalized treatment solutions. One of the potential biomarkers, gamma-frequency (30-80 Hz) brainwaves, are hypothesized to originate from the excitatory-inhibitory interaction between the pyramidal cells and interneurons. The imbalance between this interaction is described as a crucial pathological mechanism in neuropsychiatric conditions, including MDD, and the modulation of this pathological interaction has been investigated as a potential target. Previous studies attempted to induce gamma activity in the brain using rhythmic light and sound stimuli (GENUS - Gamma Entrainment Using Sensory stimuli) that resulted in neuroprotective effects in Alzheimer's disease (AD) patients and animal models. Here, we investigate the antidepressant, cognitive, and electrophysiological effects of the novel light therapy approach using 40 Hz masked flickering light for patients diagnosed with MDD.

METHODS AND DESIGN

Sixty patients with a current diagnosis of a major depressive episode will be enrolled in a randomized, double-blinded, placebo-controlled trial. The active treatment group will receive 40 Hz masked flickering light stimulation while the control group will receive continuous light matched in color temperature and brightness. Patients in both groups will get daily light treatment in their own homes and will attend four follow-up visits to assess the symptoms of depression, including depression severity measured by Hamilton Depression Rating Scale (HAM-D17), cognitive function, quality of life and sleep, and electroencephalographic changes. The primary endpoint is the mean change from baseline to week 6 in depression severity (HAM-D6 subscale) between the groups.

Reward Sensitivity and Noise Contribute to Negative Affective Bias: A Learning Signal Detection Theory Approach in Decision-Making

In patients with mood disorders, negative affective biases - systematically prioritising and interpreting information negatively - are common. A translational cognitive task testing this bias has shown that depressed patients have a reduced preference for a high reward under ambiguous decision-making conditions. The precise mechanisms underscoring this bias are, however, not yet understood. We therefore developed a set of measures to probe the underlying source of the behavioural bias by testing its relationship to a participant's reward sensitivity, value sensitivity and reward learning rate. One-hundred-forty-eight participants completed three online behavioural tasks: the original ambiguous-cue decision-making task probing negative affective bias, a probabilistic reward learning task probing reward sensitivity and reward learning rate, and a gambling task probing value sensitivity. We modelled the learning task through a dynamic signal detection theory model and the gambling task through an expectation-maximisation prospect theory model. Reward sensitivity from the probabilistic reward task (β = 0.131, p = 0.024) and setting noise from the probabilistic reward task (β = -0.187, p = 0.028) both predicted the affective bias score in a logistic regression. Increased negative affective bias, at least on this specific task, may therefore be driven in part by a combination of reduced sensitivity to rewards and more variable responses.

Therapeutic doses of ketamine acutely attenuate the aversive effect of losses during decision-making

The discovery of rapid-acting antidepressant, ketamine has opened a pathway to a new generation of treatments for depression, and inspired neuroscientific investigation based on a new perspective that non-adaptive changes in the intrinsic excitatory and inhibitory circuitry might underlie the pathophysiology of depression. Nevertheless, it still remains largely unknown how the hypothesized molecular and synaptic levels of changes in the circuitry might mediate behavioral and neuropsychological changes underlying depression, and how ketamine might restore adaptive behavior. Here, we used computational models to analyze behavioral changes induced by therapeutic doses of ketamine, while rhesus macaques were iteratively making decisions based on gains and losses of tokens. When administered intramuscularly or intranasally, ketamine reduced the aversiveness of undesirable outcomes such as losses of tokens without significantly affecting the evaluation of gains, behavioral perseveration, motivation, and other cognitive aspects of learning such as temporal credit assignment and time scales of choice and outcome memory. Ketamine's potentially antidepressant effect was separable from other side effects such as fixation errors, which unlike outcome evaluation, was readily countered with strong motivation to avoid errors. We discuss how the acute effect of ketamine to reduce the initial impact of negative events could potentially mediate longer-term antidepressant effects through mitigating the cumulative effect of those events produced by slowly decaying memory, and how the disruption-resistant affective memory might pose challenges in treating depression. Our study also invites future investigations on ketamine's antidepressant action over diverse mood states and with affective events exerting their impacts at diverse time scales.

Family psychoeducation in schizophrenia and schizophrenia related disorder, treatment compliance, and suicidal risk reduction: questions about their relationship from a naturalistic observation

Introduction

The Profamille V3.2 multi-family psycho-educational program directed at caregivers of relatives with schizophrenia or schizophrenia related disorder has been shown to decrease the annual prevalence of suicide attempts. It has been reported that psychoeducation of families can sometimes improve compliance with treatment. This study investigates whether the Profamille program improves compliance and thus reduces the risk of suicide among patients.

Method

This is a retrospective study of 179 groups of family caregivers, encompassing 1946 participants enrolled in Module 1 of the Profamille program and followed up one year after completion of the module. Evaluations were conducted using questionnaires filled out by family caregivers at three distinct times: prior to beginning the program, upon its completion, and again one year following its conclusion. The annual prevalence of suicide attempts was measured both before the program began and one year after its conclusion, while compliance to treatment was evaluated at the start and end of the program.

Result

After the Profamille program, the annual prevalence of suicide attempts fell by a factor of 2 (p-value = 0.00002) and patient compliance improved (p-value <0.000001). This reduction in suicide attempts was observed independently of improved compliance. Compliance seems to have an additional effect, but only after participation in the program.

Conclusion

The Profamille program reduces patients' risk of suicide even when patients are not taking the treatment. When family psychoeducation is not proposed in schizophrenia or schizophrenia related disorder, this can represent a loss of chance for patients.

Rodent tests of depression and anxiety: Construct validity and translational relevance

Behavioral testing constitutes the primary method to measure the emotional states of nonhuman animals in preclinical research. Emerging as the characteristic tool of the behaviorist school of psychology, behavioral testing of animals, particularly rodents, is employed to understand the complex cognitive and affective symptoms of neuropsychiatric disorders. Following the symptom-based diagnosis model of the DSM, rodent models and tests of depression and anxiety focus on behavioral patterns that resemble the superficial symptoms of these disorders. While these practices provided researchers with a platform to screen novel antidepressant and anxiolytic drug candidates, their construct validity-involving relevant underlying mechanisms-has been questioned. In this review, we present the laboratory procedures used to assess depressive- and anxiety-like behaviors in rats and mice. These include constructs that rely on stress-triggered responses, such as behavioral despair, and those that emerge with nonaversive training, such as cognitive bias. We describe the specific behavioral tests that are used to assess these constructs and discuss the criticisms on their theoretical background. We review specific concerns about the construct validity and translational relevance of individual behavioral tests, outline the limitations of the traditional, symptom-based interpretation, and introduce novel, ethologically relevant frameworks that emphasize simple behavioral patterns. Finally, we explore behavioral monitoring and morphological analysis methods that can be integrated into behavioral testing and discuss how they can enhance the construct validity of these tests.

Roles of the medial and lateral orbitofrontal cortex in major depression and its treatment

We describe evidence for dissociable roles of the medial and lateral orbitofrontal cortex (OFC) in major depressive disorder (MDD) from structure, functional activation, functional connectivity, metabolism, and neurochemical systems. The reward-related medial orbitofrontal cortex has lower connectivity and less reward sensitivity in MDD associated with anhedonia symptoms; and the non-reward related lateral OFC has higher functional connectivity and more sensitivity to non-reward/aversive stimuli in MDD associated with negative bias symptoms. Importantly, we propose that conventional antidepressants act to normalize the hyperactive lateral (but not medial) OFC to reduce negative bias in MDD; while other treatments are needed to operate on the medial OFC to reduce anhedonia, with emerging evidence suggesting that ketamine may act in this way. The orbitofrontal cortex is the key cortical region in emotion and reward, and the current review presents much new evidence about the different ways that the medial and lateral OFC are involved in MDD.

Cognitive factors as mediators of the relationship between childhood trauma and depression symptoms: the mediating roles of cognitive overgeneralisation, rumination, and social problem-solving

Background: Childhood trauma has negative immediate and long-term impacts on depression. Questions remain, however, regarding the cognitive factors influencing this relationship. This study aimed to investigate the role of three cognitive factors - cognitive overgeneralisation, rumination and social problem-solving - as mediating factors in the relationship between childhood trauma and symptoms of depression.Methods: We conducted a cross-sectional study in Iran from March to July 2023. Participants (N = 227; Mean age 32.44 ± 8.95 years) with depression completed measures of childhood trauma, depression, self-overgeneralisation, cognitive errors, memory specificity, rumination and social problem-solving. The conceptual model was assessed using structural equation modelling.Results: Structural equation modelling indicated that childhood trauma had a positive direct effect on depression symptoms. Childhood trauma had a positive indirect effect on depression symptoms through both self-overgeneralisation and rumination and a negative indirect effect on depression through effective social problem-solving strategies.Conclusions: The findings suggest increased exposure to childhood trauma may be associated with elevated depression and self-overgeneralisation, rumination, and effective social problem-solving strategies may play an important role in this relationship. These findings hold potential implications for those working with patients with depression and a history of childhood trauma.

Amygdala biomarkers of treatment response in major depressive disorder: An fMRI systematic review of SSRI antidepressants

Functional neuroimaging studies have demonstrated abnormal activity and functional connectivity (FC) of the amygdala among individuals with major depressive disorder (MDD), which may be rectified with selective serotonin reuptake inhibitor (SSRI) treatment. This systematic review aimed to identify changes in the amygdala on functional magnetic resonance imaging (fMRI) scans among individuals with MDD who received SSRIs. A search for fMRI studies examining amygdala correlates of SSRI response via fMRI was conducted through OVID (MEDLINE, PsycINFO, and Embase). The end date was April 4th, 2023. In total, 623 records were screened, and 16 studies were included in this review. While the search pertained to SSRIs broadly, the included studies were escitalopram-, citalopram-, fluoxetine-, sertraline-, and paroxetine-specific. Decreases in event-related amygdala activity were found following 6-to-12-week SSRI treatment, particularly in response to negative stimuli. Eight-week courses of SSRI pharmacotherapy were associated with increased event-related amygdala FC (i.e., with the prefrontal [PFC] and anterior cingulate cortices, insula, thalamus, caudate nucleus, and putamen) and decreased resting-state effective connectivity (i.e., amygdala-PFC). Preliminary evidence suggests that SSRIs may alter amygdala activity and FC in MDD. Additional studies are needed to corroborate findings. Future research should employ long-term follow-ups to determine whether effects persist after treatment termination.

Functional brain responses to emotional faces after three to five weeks of intake of escitalopram in healthy individuals: a double-blind, placebo-controlled randomised study

Short-term intake of selective serotonin reuptake inhibitors (SSRIs) modulates threat-related amygdala responses in healthy individuals. However, how SSRI intake over a clinically relevant time period modulates threat-related amygdala responses is less clear. In a semi-randomised, double-blind, placebo-controlled study of 64 healthy individuals (SSRI n = 32, placebo n = 32), we examined the effect of 3-5 weeks of SSRI escitalopram (20 mg daily) on brain response to angry, fearful and neutral faces using BOLD fMRI. Data was analysed using a whole-brain region-wise approach extracting standardised effects (i.e., Cohen's D). The study was conducted at the Copenhagen University Hospital. A priori, we hypothesised that SSRI would attenuate amygdala responses to angry and fearful faces but not to neutral ones. Whether SSRI modulates correlations between amygdala responses to emotional faces and negative mood states was also explored. Compared to placebo, 3-5 weeks of SSRI intake did not significantly affect the amygdala response to angry, fearful, or neutral faces (|Cohen's D|< 0.2, PFWER = 1). Whole-brain, region-wise analyses revealed significant differences in frontal (|Cohen's D|< 0.6, PFWER < .01) and occipital regions (|Cohen's D|< 0.5, PFWER < .01). SSRI did not modulate correlations between amygdala responses to emotional faces and negative mood states. Our findings indicate that a 3-5 week SSRI intake impacts cortical responses to emotional stimuli, an effect possibly involved in SSRI's therapeutic efficacy.Trial registration Clinical Trials NCT04239339.

Rapid-acting antidepressant drugs modulate affective bias in rats

How rapid-acting antidepressants (RAADs), such as ketamine, induce immediate and sustained improvements in mood in patients with major depressive disorder (MDD) is poorly understood. A core feature of MDD is the prevalence of cognitive processing biases associated with negative affective states, and the alleviation of negative affective biases may be an index of response to drug treatment. Here, we used an affective bias behavioral test in rats, based on an associative learning task, to investigate the effects of RAADs. To generate an affective bias, animals learned to associate two different digging substrates with a food reward in the presence or absence of an affective state manipulation. A choice between the two reward-associated digging substrates was used to quantify the affective bias generated. Acute treatment with the RAADs ketamine, scopolamine, or psilocybin selectively attenuated a negative affective bias in the affective bias test. Low, but not high, doses of ketamine and psilocybin reversed the valence of the negative affective bias 24 hours after RAAD treatment. Only treatment with psilocybin, but not ketamine or scopolamine, led to a positive affective bias that was dependent on new learning and memory formation. The relearning effects of ketamine were dependent on protein synthesis localized to the rat medial prefrontal cortex and could be modulated by cue reactivation, consistent with experience-dependent neural plasticity. These findings suggest a neuropsychological mechanism that may explain both the acute and sustained effects of RAADs, potentially linking their effects on neural plasticity with affective bias modulation in a rodent model.

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α1-AR, α2-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

Neuropsychological Effects of Antidepressants: Translational Studies

Pharmacological treatments that improve mood were first identified serendipitously, but more than half a century later, how these drugs induce their antidepressant effects remains largely unknown. With the help of animal models, a detailed understanding of their pharmacological targets and acute and chronic effects on brain chemistry and neuronal function has been achieved, but it remains to be elucidated how these effects translate to clinical efficacy. Whilst the field has been dominated by the monoamine and neurotrophic hypotheses, the idea that the maladaptive cognitive process plays a critical role in the development and perpetuation of mood disorders has been discussed since the 1950s. Recently, studies using objective methods to quantify changes in emotional processing found acute effects with conventional antidepressants in both healthy volunteers and patients. These positive effects on emotional processing and cognition occur without a change in the subjective ratings of mood. Building from these studies, behavioural methods for animals that quantify similar cognitive affective processes have been developed. Integrating these behavioural approaches with pharmacology and targeted brain manipulations, a picture is beginning to emerge of the underlying mechanisms that may link the pharmacology of antidepressants, these neuropsychological constructs and clinical efficacy. In this chapter, we discuss findings from animal studies, experimental medicine and patients investigating the neuropsychological effects of antidepressant drugs. We discuss the possible neural circuits that contribute to these effects and discuss whether a neuropsychological model of antidepressant effects could explain the temporal differences in clinical benefits observed with conventional delayed-onset antidepressants versus rapid-acting antidepressants.

Effect of modernized collaborative care for depression on brain-derived neurotrophic factor (BDNF) and depressive symptom clusters: Data from the eIMPACT trial

Brain-derived neurotrophic factor (BDNF) levels are lower in people with depression and are normalized following pharmacological treatment. However, it is unknown if psychological treatments for depression improve BDNF and if change in BDNF is a mediator of intervention effects on depressive symptoms. Therefore, using data from the eIMPACT trial, we sought to determine the effect of modernized collaborative care for depression on 12-month changes in BDNF and cognitive/affective and somatic depressive symptom clusters and to examine whether BDNF changes mediate intervention effects on depressive symptoms. 216 primary care patients with depression from a safety net healthcare system were randomized to 12 months of the eIMPACT intervention (internet cognitive-behavioral therapy [CBT], telephonic CBT, and select antidepressant medications) or usual primary care. Plasma BDNF was measured with commercially available kits, and depressive symptom clusters were assessed by the Patient Health Questionnaire-9. The intervention did not influence BDNF but did improve both the cognitive/affective and somatic clusters over 12 months. Changes in BDNF did not mediate the intervention effect on either cluster. Our findings suggest that modernized collaborative care is an effective treatment for both the cognitive/affective and somatic symptoms of depression and that the mechanism of action is not improvements in BDNF. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02458690.

Subthreshold Depression: A Systematic Review and Network Meta-Analysis of Non-Pharmacological Interventions

Background

Subthreshold depression (StD) is considered to be the "precursor" stage of major depressive disorder (MDD), which could cause higher risk of suicide, disease burden and functional impairment. There have been various non-pharmacological interventions for StD. However, the comparison of their effectiveness still lacks sufficient evidence. We performed a systematic review and network meta-analysis to evaluate and rank the efficacy of multiple non-pharmacological interventions targeting StD.

Methods

We conducted a thorough search across various databases including PubMed, Medline, Embase, Web of Science and PsycINFO from inception to December 2022. All included studies were randomized controlled trials (RCTs) of non-pharmacological interventions for patients with StD compared with control group (CG). Several universal scales for measuring depression severity were used as efficacy outcomes. The surface under the cumulative ranking curve (SUCRA) was used to separately rank each intervention using the "Stata 17.0" software.

Results

A total of thirty-six trials were included, involving twenty-eight interventions and 7417 participants. The research found that most non-pharmacological interventions were superior to controls for StD. In each outcome evaluation by different scales for measuring depression, psychotherapy always ranked first in terms of treatment effectiveness, especially Problem-solving Therapy (PST), Behavioral Activation Therapy (BAT), Cognitive Behavioral Therapy (CBT)/Internet-based CBT (I-CBT)/Telephone-based CBT (T-CBT). Since different groups could not be directly compared, the total optimal intervention could not be determined.

Conclusion

Here, we show that psychotherapy may be the better choice for the treatment of StD. This study provides some evidence on StD management selection for clinical workers. However, to establish its intervention effect more conclusively, the content, format and operators of psychotherapy still require extensive exploration to conduct more effective, convenient and cost-effective implementation in primary healthcare. Notably, further research is also urgently needed to find the biological and neural mechanisms of StD by examining whether psychotherapy alters neuroplasticity in patients with StD.

The effect of attention bias modification on depressive symptoms in a comorbid sample: a randomized controlled trial

BACKGROUND

Studies investigating the long-term effect of attention bias modification (ABM) in clinical samples are lacking. This study investigates the 6-months follow-up effect of ABM on depressive symptoms in participant with major depressive disorder with and without comorbid disorders.

METHODS

We conducted a double-blind randomized sham-controlled trial in 101 participants between 19 November 2019, and 17 August 2021. Follow-up ended 3 April 2022. Participants were allocated to ABM or sham condition twice daily for 14 consecutive days. Primary outcomes were the total score on the Beck Depression Inventory-II (BDI-II) at 6 months, mean Brief State Rumination Inventory (BSRI) score post-treatment and reduction in BSRI post-treatment. Secondary outcome was change in attentional bias (AB). The trial was preregistered in ClinicalTrials.gov (#NCT04137367).

RESULTS

A total of 118 patients aged 18-65 years were assessed for eligibility, and 101 were randomized and subjected to intention-to-treat analyses. At 6 months, ABM had no effect on depression and anxiety compared to a sham condition. While rumination decreased during the intervention, there was no effect of condition on rumination and AB. Predictor analysis did not reveal differences between participants with ongoing major depressive episode or comorbid anxiety.

CONCLUSION

Compared to sham training, there was no effect of ABM on depressive symptoms at 6-months follow-up. Since the intervention failed at modifying AB, it is unclear whether changes in AB are related to long-term outcomes.

The effect of ketamine on affective modulation of the startle reflex and its resting-state brain correlates

Ketamine is a rapid-acting antidepressant that also influences neural reactivity to affective stimuli. However, the effect of ketamine on behavioral affective reactivity is yet to be elucidated. The affect-modulated startle reflex paradigm (AMSR) allows examining the valence-specific aspects of behavioral affective reactivity. We hypothesized that ketamine alters the modulation of the startle reflex during processing of unpleasant and pleasant stimuli and weakens the resting-state functional connectivity (rsFC) within the modulatory pathway, namely between the centromedial nucleus of the amygdala and nucleus reticularis pontis caudalis. In a randomized, double-blind, placebo-controlled, cross-over study, thirty-two healthy male participants underwent ultra-high field resting-state functional magnetic resonance imaging at 7 T before and 24 h after placebo and S-ketamine infusions. Participants completed the AMSR task at baseline and one day after each infusion. In contrast to our hypothesis, ketamine infusion did not impact startle potentiation during processing of unpleasant stimuli but resulted in diminished startle attenuation during processing of pleasant stimuli. This diminishment significantly correlated with end-of-infusion plasma levels of ketamine and norketamine. Furthermore, ketamine induced a decrease in rsFC within the modulatory startle reflex pathway. The results of this first study on the effect of ketamine on the AMSR suggest that ketamine might attenuate the motivational significance of pleasant stimuli in healthy participants one day after infusion.

Prediction of postpartum depression with an online neurocognitive risk screening tool for pregnant women

Postpartum depression (PPD) is a severe mental illness affecting 10-15% of mothers. Emerging evidence indicates that negative neurocognitive bias in response to infant distress during pregnancy marks an increased risk of PPD. This proof-of-concept study aimed to investigate the association between negatively biased neurocognitive processing of infant distress during pregnancy and subsequent PPD and to explore the feasibility of an online risk screening tool. In the second or third trimester of pregnancy, 87 participants underwent two online tests of reactivity to and evaluation of infant distress and completed questionnaires regarding psychosocial risk factors. After birth, participants rated their depressive symptoms online and underwent a diagnostic telephone interview concerning PPD. Irrespective of depressive symptoms during pregnancy, negative reactivity to and evaluation of infant distress predicted PPD (reactivity: Exp(B)=1.33, p = 0.04) and depressive symptoms after birth (reactivity: B = 0.04, p = 0.048; evaluation: B = 0.10, p = 0.04). The negative reactivity toward infant distress showed high sensitivity and moderate specificity (89% and 77%, respectively), while the evaluation of infant distressed cries showed lower sensitivity and specificity (67% and 66%, respectively). The relatively small sample size prevented the inclusion of additional risk variables in the regression models. The replication of an association between negative neurocognitive bias during pregnancy with PPD risk is noteworthy and has clinical implications in terms of early prevention. However, the low response rate indicates that this tool is not feasible in its current form. Future larger-scale studies are needed to further investigate candidate risk factors in a brief online screening tool.

The pharmacological bases for repurposing statins in depression: a review of mechanistic studies

Statins are commonly prescribed medications widely investigated for their potential actions on the brain and mental health. Pre-clinical and clinical evidence suggests that statins may play a role in the treatment of depressive disorders, but only the latter has been systematically assessed. Thus, the physiopathological mechanisms underlying statins' putative antidepressant or depressogenic effects have not been established. This review aims to gather available evidence from mechanistic studies to strengthen the pharmacological basis for repurposing statins in depression. We used a broad, well-validated search strategy over three major databases (Pubmed/MEDLINE, Embase, PsychINFO) to retrieve any mechanistic study investigating statins' effects on depression. The systematic search yielded 8068 records, which were narrowed down to 77 relevant papers. The selected studies (some dealing with more than one bodily system) described several neuropsychopharmacological (44 studies), endocrine-metabolic (17 studies), cardiovascular (6 studies) and immunological (15 studies) mechanisms potentially contributing to the effects of statins on mood. Numerous articles highlighted the beneficial effect of statins on depression, particularly through positive actions on serotonergic neurotransmission, neurogenesis and neuroplasticity, hypothalamic-pituitary axis regulation and modulation of inflammation. The role of other mechanisms, especially the association between statins, lipid metabolism and worsening of depressive symptoms, appears more controversial. Overall, most mechanistic evidence supports an antidepressant activity for statins, likely mediated by a variety of intertwined processes involving several bodily systems. Further research in this area can benefit from measuring relevant biomarkers to inform the selection of patients most likely to respond to statins' antidepressant effects while also improving our understanding of the physiopathological basis of depression.

An online experimental medicine trial on the effect of 28-day simvastatin administration on emotional processing, reward learning, working memory and salivary cortisol in healthy volunteers at risk for depression: OxSTEP protocol

BACKGROUND

Evidence suggests inflammation may be a key mechanism by which psychosocial stress, including loneliness, predisposes to depression. Observational and clinical studies have suggested simvastatin, with its anti-inflammatory properties, may have a potential use in the treatment of depression. Previous experimental medicine trials investigating 7-day use of statins showed conflicting results, with simvastatin displaying a more positive effect on emotional processing compared with atorvastatin. It is possible that statins require longer administration in predisposed individuals before showing the expected positive effects on emotional processing.

AIMS

Here, we aim to test the neuropsychological effects of 28-day simvastatin administration versus placebo, in healthy volunteers at risk for depression owing to loneliness.

METHOD

This is a remote experimental medicine study. One hundred participants across the UK will be recruited and randomised to either 28-day 20 mg simvastatin or placebo in a double-blind fashion. Before and after administration, participants will complete an online testing session involving tasks of emotional processing and reward learning, processes related to vulnerability to depression. Working memory will also be assessed and waking salivary cortisol samples will be collected. The primary outcome will be accuracy in identifying emotions in a facial expression recognition task, comparing the two groups across time.

Multispecies probiotic administration reduces emotional salience and improves mood in subjects with moderate depression: a randomised, double-blind, placebo-controlled study

BACKGROUND

The potential antidepressant properties of probiotics have been suggested, but their influence on the emotional processes that may underlie this effect is unclear.

METHODS

Depressed volunteers (n = 71) were recruited into a randomised double-blind, placebo-controlled study to explore the effects of a daily, 4-week intake of a multispecies probiotic or placebo on emotional processing and cognition. Mood, anxiety, positive and negative affect, sleep, salivary cortisol and serum C-reactive peptide (CRP) were assessed before and after supplementation.

RESULTS

Compared with placebo, probiotic intake increased accuracy at identifying faces expressing all emotions (+12%, p < 0.05, total n = 51) and vigilance to neutral faces (mean difference between groups = 12.28 ms ± 6.1, p < 0.05, total n = 51). Probiotic supplementation also reduced reward learning (-9%, p < 0.05, total n = 51), and interference word recall on the auditory verbal learning task (-18%, p < 0.05, total n = 50), but did not affect other aspects of cognitive performance. Although actigraphy revealed a significant group × night-time activity interaction, follow up analysis was not significant (p = 0.094). Supplementation did not alter salivary cortisol or circulating CRP concentrations. Probiotic intake significantly reduced (-50% from baseline, p < 0.05, n = 35) depression scores on the Patient Health Questionnaire-9, but these did not correlate with the changes in emotional processing.

CONCLUSIONS

The impartiality to positive and negative emotional stimuli or reward after probiotic supplementation have not been observed with conventional antidepressant therapies. Further studies are required to elucidate the significance of these changes with regard to the mood-improving action of the current probiotic.

Unblinding and demand characteristics in the treatment of depression

Blinding of treatment allocation in clinical trials in psychiatry is regarded as an ideal. The potential impact of unblinding chimes with a general concern for psychological research: so-called demand characteristics can undermine confidence in findings from experimental and clinical studies. Scepticism can result in nihilism. The reliance on subjective report of symptoms in clinical trials of drug efficacy in depression provides an important example. It is regularly implied that if subjective effects, including specific adverse reactions, unblind participants to an active treatment then evidence for its efficacy is suspect. In fact, the strong association between dose and subjective effects does not translate into a strong relationship with efficacy in randomised controlled trials (RCTs) of conventional antidepressant drugs; this observation falsifies the proposition that unblinding is the principal mechanism driving RCT outcomes in studies of depression. Instead, changes in brain function, that occur soon after treatment starts, do predict treatment outcomes and align with our understanding of neurotransmitter effects from neuroscience. Psychedelic experience for the treatment of depression must be unblinding, but the effect results directly from serotonergic receptor activation and changes in brain connectivity. Where such effects are part of a novel mechanism of action, a strong dose response relationship would be expected, irrespective of unblinding. We highlight the importance of exploring blinding as a mechanism, confirming dose-related outcomes, and dissociating unblinding effects from efficacy. Unblinding does not necessarily invalidate the subjective experience of sustained recovery from depression.

Use of experimental medicine approaches for the development of novel psychiatric treatments based on orexin receptor modulation

Despite progress in understanding the pathological mechanisms underlying psychiatric disorders, translation from animal models into clinical use remains a significant bottleneck. Preclinical studies have implicated the orexin neuropeptide system as a potential target for psychiatric disorders through its role in regulating emotional, cognitive, and behavioral processes. Clinical studies are investigating orexin modulation in addiction and mood disorders. Here we review performance-outcome measures (POMs) arising from experimental medicine research methods which may show promise as markers of efficacy of orexin receptor modulators in humans. POMs provide objective measures of brain function, complementing patient-reported or clinician-observed symptom evaluation, and aid the translation from preclinical to clinical research. Significant challenges include the development, validation, and operationalization of these measures. We suggest that collaborative networks comprising clinical practitioners, academics, individuals working in the pharmaceutical industry, drug regulators, patients, patient advocacy groups, and other relevant stakeholders may provide infrastructure to facilitate validation of experimental medicine approaches in translational research and in the implementation of these approaches in real-world clinical practice.

Anhedonia and sensitivity to punishment in schizophrenia, depression and opiate use disorder

BACKGROUND

From a behavioural perspective anhedonia is defined as diminished interest in the engagement of pleasurable activities. Despite its presence across a range of psychiatric disorders, the cognitive processes that give rise to anhedonia remain unclear.

METHODS

Here we examine whether anhedonia is associated with learning from positive and negative outcomes in patients diagnosed with major depression, schizophrenia and opiate use disorder alongside a healthy control group. Responses in the Wisconsin Card Sorting Test - a task associated with healthy prefrontal cortex function - were fitted to the Attentional Learning Model (ALM) which separates learning from positive and negative feedback.

RESULTS

Learning from punishment, but not from reward, was negatively associated with anhedonia beyond other socio-demographic, cognitive and clinical variables. This impairment in punishment sensitivity was also associated with faster responses following negative feedback, independently of the degree of surprise.

LIMITATIONS

Future studies should test the longitudinal association between punishment sensitivity and anhedonia also in other clinical populations controlling for the effect of specific medications.

CONCLUSIONS

Together the results reveal that anhedonic subjects, because of their negative expectations, are less sensitive to negative feedbacks; this might lead them to persist in actions leading to negative outcomes.

Investigating neuropsychological and reward-related deficits in a chronic corticosterone-induced model of depression

Chronic stress is a known risk factor for the development of major depression (MDD) and is commonly used to induce a depression-like phenotype in rodents. Similar phenotypic effects are also observed in rodents when treated chronically with the stress hormone corticosterone. In this study, we investigated the neuropsychological consequences of chronic corticosterone treatment in male rats using two translational rodent assays of affective bias, the judgement bias task (JBT) and affective bias test (ABT). We also used the reward learning assay (RLA) and sucrose preference test (SPT) to quantify reward-related behaviours. Negative biases in decision-making were observed in the chronic corticosterone-treated group but only when the treatment was given shortly before each behavioural session. The same dose of corticosterone, when given daily after completion of the behavioural session had no effects. Chronic corticosterone treatment did not potentiate negative affective biases in the ABT induced by either an acute pharmacological or stress manipulation but both reward learning and reward sensitivity were blunted. Analysis of the brain tissue from animals receiving chronic corticosterone found reduced hippocampal neurogenesis consistent with previous studies suggesting corticosterone-induced neurotrophic deficits. Taken together, these data suggest chronic corticosterone treatment induces neuropsychological effects related to changes in reward learning, memory and negative biases in decision making, but these decision-making biases depend on whether rewarding outcomes were experienced during the acute effects of the drug. These findings suggest an important interaction between psychological and biological factors resulting in negative biases in decision-making in this model.

The Use of Psychotropic Medication in Pediatric Oncology for Acute Psychological and Psychiatric Problems: Balancing Risks and Benefits

Severe acute behavioral and emotional problems represent one of the most serious treatment-related adverse effects for children and adolescents who have cancer. The critical and severe nature of these symptoms often makes necessary the use of psychotropic drugs. A working group composed of experts in multiple disciplines had the task of creating an agreement regarding a management plan for severe acute behavioral and emotional problems (SABEPs) in children and adolescents treated for cancer. To obtain global information on the use of psychotropic drugs in pediatric oncology, the working group first developed and mailed a 15-item questionnaire to many Italian pediatric oncology centers. Overall, an evident lack of knowledge and education regarding the use of psychotropic medications for the treatment of SABEPs was found. Thus, by referring to an adapted version of the Delphi method of consensus and standard methods for the elaboration of clinical questions (PICOs), the working group elaborated evidence-based recommendations for psychotropic drugs in the pediatric oncology setting. Furthermore, based on a thorough multivariate analysis of needs and difficulties, a comprehensive management flow was developed to optimize therapeutic interventions, which allows more accurate and efficient matching of the acute needs of patients while guiding treatment options.

Exploring the Mechanism of Action of Trachelospermi Caulis et Folium for Depression Based on Experiments: Combining Network Pharmacology and Molecular Docking

Objective

To reveal the safety, efficacy, and mechanism of action of Trachelospermi Caulis et Folium (TCEF) for treating depression.

Methods

The maximum dose method was employed to evaluate the safety of TCEF, and its antidepressant activity was assessed using the tail suspension and sugar water depletion tests. The main components of TCEF were determined using ultrahigh performance liquid chromatography coupled with quadrupole exactive orbitrap mass spectrometer (UHPLC-Q-EOMS). The active ingredients and their action targets were obtained using network pharmacology with SwissADME and SwissTargetPrediction screening, and the targets of depression were obtained using GeneCards, DrugBank, etc. The drug and depression-related targets were intersected and analyzed via PPI network, GO, and KEGG. Subsequently, the binding ability of the core components of TCEF to the core targets was validated via molecular docking and simulation.

Results

No statistically significant difference was observed between the normal and TCEF groups in terms of body weight, visceral index, and biochemical parameters (P > 0.05). Compared with the model group, all dose groups of TCEF had reduced the immobility time of tail suspension (P < 0.05) and increased the rate of sugar water consumption (P < 0.05). UHPLC-Q-EOMS was employed to identify 59 major components of TCEF, and network pharmacology analysis was used to screen 48 active components of TCEF for treating depression, corresponding to 139 relevant targets, including ALB, AKT1, TNF, ESR1, and CTNNB1. The involved pathways include neuroactive ligand-receptor interaction. The molecular docking results indicated that the core components have a good binding activity to the core targets.

Conclusions

TCEF is a relatively safe antidepressant medicine that exerts therapeutic effects through multiple components, targets, and pathways, providing a new idea and theoretical basis for future use of TCEF to treat depression.

Evaluating cognitive disturbances as treatment target and predictor of antidepressant action in major depressive disorder: A NeuroPharm study

Cognitive disturbances in major depressive disorder (MDD) constitute a critical treatment target and hold promise as an early predictor of antidepressant treatment response; yet their clinical relevance is not fully established. Therefore, we here investigate if (1) cognitive performance improves over the course of antidepressant treatment and (2) cognitive performance at baseline is predictive of antidepressant treatment response. In the NeuroPharm study (clinical trial id: NCT02869035), 92 antidepressant-free patients with a moderate to severe depressive episode were assessed with a comprehensive cognitive test battery including both cold (emotion-independent) and hot (emotion-dependent) tasks. Patients were tested before and after 12 weeks of standard antidepressant treatment with escitalopram in flexible doses of 10-20 mg. Performance improved across most cognitive domains over the course of antidepressant treatment. Notably, these improvements were independent of improvement in mood symptoms, emphasizing that cognitive disturbances are a distinct symptom and therefore treatment target in MDD. Results did not suggest that performance on any single cognitive measure at baseline was associated with later clinical response to antidepressant treatment. However, a small cluster of patients (N = 28) with globally disturbed cognition at baseline exhibited poorer clinical response after 8 but not 12 weeks of antidepressant treatment, suggesting that severe cognitive disturbances may delay treatment response. Thus, while pretreatment cognitive performance on individual tests may not be useful as clinical markers of treatment response, profiles capturing performance across different cognitive domains may be useful for stratification of patients with MDD and could be helpful in future intervention trials.

Nonpharmacological interventions for subthreshold depression in adults: A systematic review and network meta-analysis

Subthreshold depression (StD) is very common, with an estimated global incidence of 25%, and is associated with other clinical conditions. Nonpharmacological interventions have been demonstrated to be effective, but which one is best should be further investigated. This study aims to compare and rank the efficacy of nonpharmacological interventions in adults with StD. Ten databases were searched, and comparisons were made using a random-effects network meta-analysis using the frequentist framework. The assumption of local consistency was assessed by using the node-splitting method. The surface under the cumulative ranking curve (SUCRA) was used to separately rank each intervention. A total of 32 randomized controlled trials (RCTs) were included. The results showed that psychotherapy, as an intervention class, had significantly positive effects compared to control groups (SMD = -0.78, 95% CI: -1.06, -0.49) and had the highest rank (SUCRA, 79.0%; mean rank, 1.6). Cognitive behavioral therapy (CBT), as an individual intervention, had significantly positive effects relative to all control groups and had the highest rank (SUCRA, 82.5%; mean rank, 3.1). We speculate that psychotherapy, especially CBT, may be the most effective nonpharmacological intervention to improve StD in adults. More RCTs examining the efficacy of different nonpharmacological interventions are needed.

Evaluation of Early Ketamine Effects on Belief-Updating Biases in Patients With Treatment-Resistant Depression

IMPORTANCE

Clinical research has shown that persistent negative beliefs maintain depression and that subanesthetic ketamine infusions induce rapid antidepressant responses.

OBJECTIVE

To evaluate whether ketamine alters belief updating and how such cognitive effects are associated with the clinical effects of ketamine.

DESIGN, SETTING, AND PARTICIPANTS

This study used an observational case-control protocol with a mixed-effects design that nested 2 groups by 2 testing time points. Observers were not blinded. Patients with treatment-resistant depression (TRD) and healthy volunteer participants aged 34 to 68 years were included. Patients with TRD were diagnosed with major depressive disorder or bipolar depression, had a Montgomery-Åsberg Depression Rating Scale score greater than 20, a Maudsley Staging Method score greater than 7, and failed to respond to at least 2 prior antidepressant trials. Exclusion criteria were any other psychiatric, neurological, or neurosurgical comorbidities, substance use or addictive disorders, and recreational ketamine consumption. Data were collected from January to February 2019 and from May to December 2019, and data were analyzed from January 2020 to July 2021.

EXPOSURES

Patients with TRD were observed 24 hours before single ketamine infusion, 4 hours after the infusion, and 4 hours after the third infusion, which was 1 week after the first infusion. Healthy control participants were observed twice 1 week apart without ketamine exposure.

MAIN OUTCOMES AND MEASURES

Montgomery-Åsberg Depression Rating Scale score and belief updating after belief updating when patients received good news and bad news measured by a cognitive belief-updating task and mathematically formalized by a computational reinforcement learning model.

RESULTS

Of 56 included participants, 29 (52%) were male, and the mean (SEM) age was 52.3 (1.2) years. A total of 26 patients with TRD and 30 control participants were included. A significant group × testing time point × news valence interaction showed that patients with TRD updated their beliefs more after good than bad news following a single ketamine infusion (controlled for age and education: β = -0.91; 95% CI, -1.58 to -0.24; t216 = -2.67; P = .008) than controls. Computational modeling showed that this effect was associated with asymmetrical learning rates (LRs) after ketamine treatment (good news LRs after ketamine, 0.51 [SEM, 0.04]; bad news LRs after ketamine 0.36 [SEM, 0.03], t25 = 3.8; P < .001) and partially mediated early antidepressant responses (path a*b: β = -1.00 [SEM, 0.66]; t26 = -1.53; z = -1.98; P = .04).

CONCLUSIONS AND RELEVANCE

These findings provide novel insights into the cognitive mechanisms of the action of ketamine in patients with TRD, with promising perspectives for augmented psychotherapy for individuals with mood disorders.

Statins in depression: a repurposed medical treatment can provide novel insights in mental health

Depression has a large burden, but the development of new drugs for its treatment has proved difficult. Progresses in neuroscience have highlighted several physiopathological pathways, notably inflammatory and metabolic ones, likely involved in the genesis of depressive symptoms. A novel strategy proposes to repurpose established medical treatments of known safety and to investigate their potential antidepressant activity. Among numerous candidates, growing evidence suggests that statins may have a positive role in the treatment of depressive disorders, although some have raised concerns about possible depressogenic effects of these widely prescribed medications. This narrative review summarises relevant findings from translational studies implicating many interconnected neurobiological and neuropsychological, cardiovascular, endocrine-metabolic, and immunological mechanisms by which statins could influence mood. Also, the most recent clinical investigations on the effects of statins in depression are presented. Overall, the use of statins for the treatment of depressive symptoms cannot be recommended based on the available literature, though this might change as several larger, methodologically robust studies are being conducted. Nevertheless, statins can already be acknowledged as a driver of innovation in mental health, as they provide a novel perspective to the physical health of people with depression and for the development of more precise antidepressant treatments.

Sex differences in inflammation in the hippocampus and amygdala across the lifespan in rats: associations with cognitive bias

Background

Cognitive symptoms of major depressive disorder, such as negative cognitive bias, are more prevalent in women than in men. Cognitive bias involves pattern separation which requires hippocampal neurogenesis and is modulated by inflammation in the brain. Previously, we found sex differences in the activation of the amygdala and the hippocampus in response to negative cognitive bias in rats that varied with age. Given the association of cognitive bias to neurogenesis and inflammation, we examined associations between cognitive bias, neurogenesis in the hippocampus, and cytokine and chemokine levels in the ventral hippocampus (HPC) and basolateral amygdala (BLA) of male and female rats across the lifespan.

Results

After cognitive bias testing, males had more IFN-γ, IL-1β, IL-4, IL-5, and IL-10 in the ventral HPC than females in adolescence. In young adulthood, females had more IFN-γ, IL-1β, IL-6, and IL-10 in the BLA than males. Middle-aged rats had more IL-13, TNF-α, and CXCL1 in both regions than younger groups. Adolescent male rats had higher hippocampal neurogenesis than adolescent females after cognitive bias testing and young rats that underwent cognitive bias testing had higher levels of hippocampal neurogenesis than controls. Neurogenesis in the dorsal hippocampus was negatively associated with negative cognitive bias in young adult males.

Conclusions

Overall, the association between negative cognitive bias, hippocampal neurogenesis, and inflammation in the brain differs by age and sex. Hippocampal neurogenesis and inflammation may play greater role in the cognitive bias of young males compared to a greater role of BLA inflammation in adult females. These findings lay the groundwork for the discovery of sex-specific novel therapeutics that target region-specific inflammation in the brain and hippocampal neurogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00299-4.

• Adolescent male rats had more hippocampal inflammation than females after cognitive bias testing.

• Adult female rats had more basolateral amygdalar inflammation than males after cognitive bias testing.

• HPC neurogenesis was negatively associated to cognitive bias in young adult male rats.

Associations Between Statin Use and Negative Affective Bias During COVID-19: An Observational, Longitudinal UK Study Investigating Depression Vulnerability

BACKGROUND

There is growing interest in the antidepressant potential of statins. We tested whether statin use is associated with cognitive markers previously found to indicate psychological vulnerability to depression within the context of the COVID-19 pandemic.

METHODS

Between April 2020 and February 2021, we conducted an observational online study of 2043 adults in the United Kingdom. Participants completed cognitive tasks assessing processes related to depression vulnerability, including affective bias and reward processing. We also measured working memory, medication use, and current psychiatric symptoms. Using mixed analysis of covariance and regression models, we compared participants on statins alone (n = 81), antihypertensive medication alone (n = 126), both medications (n = 111), and on neither medication (n = 1725).

RESULTS

Statin use was associated with reduced recognition of angry and fearful faces (F₁ = 9.19, p = .002; F₁ = 6.9, p = .009) and with increased misclassification of these expressions as positive. Increased recognition of angry faces at baseline predicted increased levels of depression and anxiety 10 months later (β = 3.61, p = .027; β = 2.37, p = .002). Statin use was also associated with reduced learning about stimuli associated with loss (F_1,1418 = 9.90, p = .002). These indicators of reduced negative bias were not seen in participants taking antihypertensive medication alone, suggesting that they were related to statin use in particular rather than nonspecific demographic factors. In addition, we found no evidence of an association between statin use and impairment in working memory.

CONCLUSIONS

Statin use was associated with cognitive markers indicative of reduced psychological vulnerability to depression, supporting their potential use as a prophylactic treatment for depression.

Regulation of Antidepressant Prescription for the Effective Treatment of Mental Disorders in Turkey: A Narrative Review

Background

This non-systematic narrative review aims to summarize the results of clinical studies evaluating the effectiveness of antidepressants used to treat mental illnesses including major depressive disorder, obsessive-compulsive disorder, somatization disorder, and anxiety disorders in Turkey. Conclusions drawn from this article can guide ongoing efforts by Turkish health policymakers to improve public health development in the country by further regulating the prescription of antidepressants.

Methods

Relevant articles regarding the effectiveness of antidepressant use were collected in June 2021 using Cumulative Index to Nursing and Allied Health Literature (CINAHL) Plus and Academic Search Complete online databases. The collected articles were then appraised using the Critical Appraisal Skills Programme to determine the reliability and quality of each article and to assess the risk of bias in each article. The summary of key findings/evidence, Critical Appraisal Skills Programme appraisal summary results, funding, study designs applied, settings covered, period covered (years), and additional comments were extracted from each article for analysis. The inclusion criteria involved articles that recounted adverse effects and effectiveness of antidepressant use in Turkey to treat mental illnesses, including anxiety disorders, major depressive disorder, somatization disorder, and obsessive-compulsive disorder. The exclusion criteria consisted of articles that included participants who resided outside of the geographic region of Turkey, abstracts, the pharmacology of antidepressant use, antidepressant off-label use, and alternative treatments.

Results

A total of 15 articles out of the 104 derived from the databases were included in the study that fell into 1 of the following main themes, "adverse effects" and "mixed results," which accounted for 53% (8 articles) and 40% (6 articles), respectively. One outlying article was identified (7%).

Conclusions

Totally 8 out of 15 articles that recounted antidepressants prescribed for mental illnesses produced adverse effects without treatment success and 6 out of 15 articles recounted adverse effects with treatment success. One outlying article found a confound that precluded determining whether an adverse effect was caused by antidepressant use or confounded by pre-existing conditions. Given that 14 out of 15 articles recounted adverse effects associated with antidepressant use and 6 out of 15 articles recounted antidepressant treatment success, Turkish policymakers are encouraged to adopt a restrictive drug policy strategy. To sum up, antidepressant prescription and consumption should be conducted with caution to limit unnecessary risk of exposure to adverse effects associated with antidepressant use. Limitations in the research included using a non-systematic tool instead of conducting a systematic review, a limited number of articles (15 out of 104), and risk of bias was detected from appraising the articles via Critical Appraisal Skills Programme.

Escitalopram should be investigated in anorexia nervosa: Rationale and review of mechanisms

One of the biggest ambitions in the field of anorexia nervosa (AN) research is to find a reliable and effective pharmacological treatment. The fact that currently no pharmacological treatment is safe and effective in this disease is worrying and also challenging. On the basis of the progress in our understanding of AN neurobiology, we propose that escitalopram, a widely available drug, might be a safe and effective option that needs to be investigated. Escitalopram is the only selective serotonin reuptake inhibitor, without any catecholaminergic effect. As studies have shown decreased serotonergic and increased dopaminergic transmission in AN, we hypothesized that an ideal drug for AN management should boost serotonin levels to increase serotonergic and decrease dopaminergic transmission, the two main features of escitalopram action. Here, we present a short overview of pharmacological research in AN and discuss the theoretical rationale for escitalopram use in AN. We also call for double-blind, randomized, placebo-controlled trials to test whether this theoretical framework translates into clinical efficacy.

Relationship between change in social evaluation learning and mood in early antidepressant treatment: A prospective cohort study in primary care

BACKGROUND

Antidepressants are proposed to work by increasing sensitivity to positive versus negative information. Increasing positive affective learning within social contexts may help remediate negative self-schema. We investigated the association between change in biased learning of social evaluations about the self and others, and mood during early antidepressant treatment.

METHOD

Prospective cohort assessing patients recruited from primary care in South West England at four timepoints over the first 8 weeks of antidepressant treatment (n = 29). At each timepoint, participants completed self-report measures of depression (Beck Depression Inventory II (BDI-II) and Patient Health Questionnaire 9 (PHQ-9)), anxiety (Generalised Anxiety Disorder Questionnaire 7 (GAD-7)), and a computerised task measuring learning of social evaluations about the self, a friend and a stranger.

RESULTS

We did not find evidence that learning about the self was associated with a reduction in PHQ-9 (b = 0.08, 95% CI: -0.05, 0.20, p = 0.239) or BDI-II scores (b = 0.10, 95% CI: -0.18, 0.38, p = 0.469). We found some weak evidence that increased positive learning about the friend was associated with a reduction in BDI-II scores (b = 0.30, 95% CI: -0.02, 0.62, p = 0.069). However, exploratory analyses indicated stronger evidence that increased positive learning about the self (b = 0.18, 95% CI: 0.07, 0.28, p = 0.002) and a friend (b = 0.22, 95% CI: 0.10, 0.35, p = 0.001) was associated with reductions in anxiety.

CONCLUSIONS

Change in social evaluation learning was associated with a reduction in anxiety but not depression. Antidepressants may treat anxiety symptoms by remediating negative affective biases towards socially threatening information directed towards the self and close others. However, our findings are based on exploratory analyses within a small sample without a control group and are therefore at risk of type 1 errors and order effects. Further research with larger samples is required.

Serotonin modulates asymmetric learning from reward and punishment in healthy human volunteers

Instrumental learning is driven by a history of outcome success and failure. Here, we examined the impact of serotonin on learning from positive and negative outcomes. Healthy human volunteers were assessed twice, once after acute (single-dose), and once after prolonged (week-long) daily administration of the SSRI citalopram or placebo. Using computational modelling, we show that prolonged boosting of serotonin enhances learning from punishment and reduces learning from reward. This valence-dependent learning asymmetry increases subjects' tendency to avoid actions as a function of cumulative failure without leading to detrimental, or advantageous, outcomes. By contrast, no significant modulation of learning was observed following acute SSRI administration. However, differences between the effects of acute and prolonged administration were not significant. Overall, these findings may help explain how serotonergic agents impact on mood disorders.

An experimental medicine study of the effects of simvastatin on emotional processing, reward learning, verbal memory, and inflammation in healthy volunteers

RATIONALE

Clinical studies suggest that the highly lipophilic, anti-inflammatory molecule, simvastatin, might be an ideal candidate for drug repurposing in the treatment of depression. The neuropsychological effects of simvastatin are not known, but their ascertainment would have significant translational value about simvastatin's influence on mood and cognition.

OBJECTIVES

We aimed to investigate the effects of simvastatin on a battery of psychological tests and inflammatory markers in healthy volunteers.

METHODS

Fifty-three healthy subjects were randomly assigned to 7 days of either simvastatin (N = 27) or sucrose-based placebo (N = 26) given in a double-blind fashion. Then, participants were administered questionnaires measuring subjective rates of mood and anxiety, and a battery of tasks assessing emotional processing, reward learning, and verbal memory. Blood samples for C-reactive protein were also collected.

RESULTS

Compared to placebo, participants on simvastatin showed a higher number of positively valenced intrusions in the emotional recall task (F1,51 = 4.99, p = 0.03), but also an increase in anxiety scores (F1,51 = 5.37, p = 0.02). An exploratory analysis of the females' subgroup (N = 27) showed lower number of misclassifications as sad facial expression in the simvastatin arm (F1,25 = 6.60, p = 0.02). No further statistically significant changes could be observed on any of the other outcomes measured.

CONCLUSIONS

We found limited evidence that 7-day simvastatin use in healthy volunteer induces a positive emotional bias while also being associated with an increase in anxiety, potentially reflecting the early effects of antidepressants in clinical practice. Such effect might be more evident in female subjects. Different drug dosages, treatment lengths, and sample selection need consideration in further experimental medicine and clinical studies.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT04652089.

Brain serotonin transporter is associated with cognitive-affective biases in healthy individuals

Cognitive affective biases describe the tendency to process negative information or positive information over the other. These biases can be modulated by changing extracellular serotonin (5-HT) levels in the brain, for example, by pharmacologically blocking and downregulating the 5-HT transporter (5-HTT), which remediates negative affective bias. This suggests that higher levels of 5-HTT are linked to a priority of negative information over positive, but this link remains to be tested in vivo in healthy individuals. We, therefore, evaluated the association between 5-HTT levels, as measured with [¹¹ C]DASB positron emission tomography (PET), and affective biases, hypothesising that higher 5-HTT levels are associated with a more negative bias. We included 98 healthy individuals with measures of [¹¹ C]DASB binding potential (BP_ND ) and affective biases using The Emotional Faces Identification Task by subtracting the per cent hit rate for happy from that of sad faces (EFIT_AB ). We evaluated the association between [¹¹ C]DASB BP_ND and EFIT_AB in a linear latent variable model, with the latent variable (5-HTT_LV ) modelled from [¹¹ C]DASB BP_ND in the fronto-striatal and fronto-limbic networks implicated in affective cognition. We observed an inverse association between 5-HTT_LV and EFIT_AB (β = -8% EFIT_AB per unit 5-HTT_LV , CI = -14% to -3%, p = .002). These findings show that higher 5-HTT levels are linked to a more negative bias in healthy individuals. High 5-HTT supposedly leads to high clearance of 5-HT, and thus, a negative bias could result from low extracellular 5-HT. Future studies must reveal if a similar inverse association exists in individuals with affective disorders.

Pro-cognitive effect of acute imipramine administration correlates with direct interaction of BDNF with its receptor, Trkβ

Given the important role of brain-derived neurotrophic factor (BDNF)-mediated Trkβ signalling in the mechanism of action of antidepressants (ADs), we examined ligand-receptor interactions in the rat cingulate cortex using a proximity ligation assay (PLA) in response to acute and repeated administration of imipramine (IMI), followed by various drug-free periods. Both the acute and chronic administration of IMI increased the BDNF-Trkβ interaction observed 3 h after drug administration. Withdrawal of IMI for 72 h or 7 days did not alter BDNF-Trkβ interaction. A significant reduction in this interaction after chronic IMI administration followed by 21 drug-free days was observed, but it returned to the control value when a new dose of IMI was given after this time. The level of mRNA encoding BDNF or Trkβ did not change in the experimental groups of animals, so one can conclude that alterations in the BDNF-Trkβ interaction depend not on acute vs. repeated treatment with IMI but on the presence of the drug in the body. This effect correlates well with the strong pro-cognitive effect of acute IMI, assessed by the novel object recognition (NOR) test.

The Potential Use of Ebselen in Treatment-Resistant Depression

Ebselen is an organoselenium compound developed as an antioxidant and subsequently shown to be a glutathione peroxidase (GPx) mimetic. Ebselen shows some efficacy in post-stroke neuroprotection and is currently in trial for the treatment and prevention of hearing loss, Meniere's Disease and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In vitro screening studies show that ebselen is also an effective inhibitor of the enzyme inositol monophosphatase (IMPase), which is a key target of the mood-stabilising drug lithium. Further, in animal experimental studies, ebselen produces effects on the serotonin system very similar to those of lithium and also decreases behavioural impulsivity. The antidepressant effects of lithium in treatment-resistant depression (TRD) have been attributed to its ability to facilitate presynaptic serotonin activity; this suggests that ebselen might also have a therapeutic role in this condition. Human studies utilising magnetic resonance spectroscopy support the notion that ebselen, at therapeutic doses, inhibits IMPase in the human brain. Moreover, neuropsychological studies support an antidepressant profile for ebselen based on positive effects on emotional processing and reward seeking. Ebselen also lowers a human laboratory measure of impulsivity, a property that has been associated with lithium's anti-suicidal effects in patients with mood disorders. Current clinical studies are directed towards assessment of the neuropsychological effects of ebselen in TRD patients. It will also be important to ascertain whether ebselen is able to lower impulsivity and suicidal behaviour in clinical populations. The objective of this review is to summarise the developmental history, pre-clinical and clinical psychopharmacological properties of ebselen in psychiatric disorders and its potential application as a treatment for TRD.

Placebo induced expectations of mood enhancement generate a positivity effect in emotional processing

A perceptual bias towards negative emotions is a consistent finding in mood disorders and a major target of therapeutic interventions. Placebo responses in antidepressant treatment are substantial, but it is unclear whether and how underlying expectancy effects can modulate response biases to emotional inputs. In a first attempt to approach this question, we investigated how placebo induced expectation can shape the perception of specific emotional stimuli in healthy individuals. In a controlled cross-over design, positive treatment expectations were induced by verbal instructions and a hidden training manipulation combined with an alleged oxytocin nasal spray before participants performed an emotion classification task on happy and fearful facial expressions with varying intensity. Analyses of response criterion and discrimination ability as derived from emotion-specific psychometric functions demonstrate that expectation specifically lowered participants’ threshold for identifying happy emotions in general, while they became less sensitive to subtle differences in emotional expressions. These indications of a positivity bias were directly correlated with participants’ treatment expectations as well as subjective experiences of treatment effects and went along with a significant mood enhancement. Our findings show that expectations can induce a perceptual positivity effect in healthy individuals which is probably modulated by top-down emotion regulation and which may be able to improve mood state. Clinical implications of these promising results now need to be explored in studies of expectation manipulation in patients with mood disorders.

A neurobiological perspective on social influence: Serotonin and social adaptation

Humans are inherently social beings. Being suggestible to each other's expectations enables pro-social skills that are crucial for social learning and adaptation. Despite its high relevance for psychiatry, the neurobiological mechanisms underlying social adaptation are still not well understood. This review therefore provides a conceptual framework covering various distinct mechanisms underlying social adaptation and explores the neuropharmacology - in particular the role of the serotonin (5-HT) system - modulating these mechanisms. This article therefore reviews empirical results on social influence processing and reconciles them with recent findings from psychedelic research on social processing to elucidate neurobiological and neuropharmacological underpinnings of social adaptation. Various computational, neurobiological, and neurochemical processes are involved in distinct mechanisms underlying social adaptation such as the multisensory process of social information integration that is crucial for the forming of self-representation and representations of social norms. This is again associated with self- and other-perception during social interactions as well as value-based decision making that guides our behaviour in daily interactions. We highlight the critical role of 5-HT in these processes and suggest that 5-HT can facilitate social learning and may represent an important target for treating psychiatric disorders characterized by impairments in social functioning. This framework also has important implications for psychedelic-assisted therapy as well as for the development of novel treatment approaches and future research directions.

Update on GPCR-based targets for the development of novel antidepressants

Traditional antidepressants largely interfere with monoaminergic transport or degradation systems, taking several weeks to have their therapeutic actions. Moreover, a large proportion of depressed patients are resistant to these therapies. Several atypical antidepressants have been developed which interact with G protein coupled receptors (GPCRs) instead, as direct targeting of receptors may achieve more efficacious and faster antidepressant actions. The focus of this review is to provide an update on how distinct GPCRs mediate antidepressant actions and discuss recent insights into how GPCRs regulate the pathophysiology of Major Depressive Disorder (MDD). We also discuss the therapeutic potential of novel GPCR targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles. Finally, we highlight recent advances in understanding GPCR pharmacology and structure, and how they may provide new avenues for drug development.

A single oral dose of citalopram increases interoceptive insight in healthy volunteers

RATIONALE

Interoception is the signalling, perception, and interpretation of internal physiological states. Many mental disorders associated with changes of interoception, including depressive and anxiety disorders, are treated with selective serotonin reuptake inhibitors (SSRIs). However, the causative link between SSRIs and interoception is not yet clear.

OBJECTIVES

To ascertain the causal effect of acute changes of serotonin levels on cardiac interoception.

METHODS

Using a within-participant placebo-controlled design, forty-seven healthy human volunteers (31 female, 16 male) were tested on and off a 20 mg oral dose of the commonly prescribed SSRI, citalopram. Participants made judgements on the synchrony between their heartbeat and auditory tones and then expressed confidence in each judgement. We measured three types of interoceptive cognition.

RESULTS

Citalopram increased cardiac interoceptive insight, measured as correspondence of self-reported confidence to the likelihood that interoceptive judgements were actually correct. This effect was driven by enhanced confidence for correct interoceptive judgements and was independent of measured cardiac and reported subjective effects of the drug.

CONCLUSIONS

An acute change of serotonin levels can increase insight into the reliability of inferences made from cardiac interoceptive sensations.