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Background: The neurocognitive model of antidepressant treatment in depression states that antidepressants work by producing relatively immediate positive shifts in emotional processing, which translate into clinical improvement with time. St John's Wort has shown antidepressant potential in randomised controlled trials; however, its pharmacological actions are broad and it is unknown whether treatment also produces changes in emotional processing.Aims: We investigated whether short-term treatment with St John's wort has similar effects on emotional processing to those reported with other antidepressants such as selective serotonergic reuptake inhibitors.Methods: Forty-eight healthy participants were given St John's wort or placebo treatment for seven days. On day 7 they completed a battery of tasks to measure emotional processing and other elements of cognition.Results: St John's wort treatment produced similar changes to other antidepressants, for example reducing recognition of disgusted faces and attention to fearful faces, while increasing memory for positive words. We failed to find evidence for an effect of St John's wort on other aspects of cognition including working memory.Conclusions: These findings lend support to the theory that the production of early positive biases in emotional processing may be a common feature of all clinically effective antidepressants with diverse pharmacological mechanisms. [ABSTRACT FROM AUTHOR]

Background: Antidepressants are licensed for use in depressive disorders, but non-response and poor adherence to treatment affect a considerable number of patients. Pre-clinical and clinical evidence suggest that statins can augment the effects of antidepressants. However, the acceptability and tolerability of combining statins with antidepressants are unclear, and their add-on efficacy has only been shown in small, short-term clinical trials. Observational data can provide complementary information about treatment effects on larger samples over longer follow-ups. In this study, we therefore assessed the real-world acceptability, tolerability, and efficacy of concomitant antidepressant and statin treatment in depression. Methods: We conducted a population-based cohort study investigating QResearch primary care research database, which comprises the anonymised electronic healthcare records of 35 + million patients over 1574 English general practices. Patients aged 18–100 years, registered between January 1998 and August 2020, diagnosed with a new episode of depression, and commencing an antidepressant were included. Using a between-subject design, we identified two study groups: antidepressant + statin versus antidepressant-only prescriptions. Outcomes of interest included the following: antidepressant treatment discontinuations due to any cause (acceptability) and due to any adverse event (tolerability) and effects on depressive symptoms (efficacy) measured as response, remission, and change in depression score on the Patient Health Questionnaire-9. All outcomes were assessed at 2, 6, and 12 months using multivariable regression analyses, adjusted for relevant confounders, to calculate adjusted odds ratios (aORs) or mean differences (aMDs) with 99% confidence intervals (99% CIs). Results: Compared to antidepressant-only (N 626,335), antidepressant + statin (N 46,482) was associated with higher antidepressant treatment acceptability (aOR2months 0.88, 99% CI 0.85 to 0.91; aOR6months 0.81, 99% CI 0.79 to 0.84; aOR12months 0.78, 99% CI 0.75 to 0.81) and tolerability (aOR2months 0.92, 99% CI 0.87 to 0.98; aOR6months 0.94, 99% CI 0.89 to 0.99, though not long term aOR12 months 1.02, 99% CI 0.97 to 1.06). Efficacy did not differ between groups (range aOR2-12 months 1.00 and 1.02 for response and remission, range aOR2-12 months − 0.01 and − 0.02 for change in depression score). Conclusions: On real-world data, there is a positive correlation between antidepressant treatment adherence and statin use, partly explained by fewer dropouts due to adverse events. The main limitation of our study is its observational design, which restricts the potential to make causal inferences. [ABSTRACT FROM AUTHOR]

Clinical depression is a common, debilitating and heterogenous disorder. Existing treatments for depression are inadequate for a significant minority of patients and new approaches are urgently needed. A wealth of evidence implicates the serotonin 1A (5-HT1A) receptor in the pathophysiology of depression. Stimulation of the 5-HT1A receptor is an existing therapeutic target for treating depression and anxiety, using drugs such as buspirone and tandospirone. However, activation of 5-HT1A raphe autoreceptors has also been suggested to be responsible for the delay in the therapeutic action of conventional antidepressants such as selective serotonin reuptake inhibitors (SSRIs). This narrative review provides a brief overview of the 5-HT1A receptor, the evidence implicating it in depression and in the effects of conventional antidepressant treatment. We highlight that pre- and post-synaptic 5-HT1A receptors may have divergent roles in the pathophysiology and treatment of depression. To date, developing this understanding to progress therapeutic discovery has been limited, partly due to a paucity of specific pharmacological probes suitable for use in humans. The development of 5-HT1A 'biased agonism', using compounds such as NLX-101, offers the opportunity to further elucidate the roles of pre- and post-synaptic 5-HT1A receptors. We describe how experimental medicine approaches can be helpful in profiling the effects of 5-HT1A receptor modulation on the different clinical domains of depression, and outline some potential neurocognitive models that could be used to test the effects of 5-HT1A biased agonists. [ABSTRACT FROM AUTHOR]

Background: Adolescent major depressive disorder (MDD) is associated with disrupted processing of emotional stimuli and difficulties in cognitive reappraisal. Little is known however about how current pharmacotherapies act to modulate the neural mechanisms underlying these key processes. The current study therefore investigated the neural effects of fluoxetine on emotional reactivity and cognitive reappraisal in adolescent depression. Methods: Thirty-one adolescents with MDD were randomised to acute fluoxetine (10 mg) or placebo. Seventeen healthy adolescents were also recruited but did not receive any treatment for ethical reasons. During functional magnetic resonance imaging (fMRI), participants viewed aversive images and were asked to either experience naturally the emotional state elicited ('Maintain') or to reinterpret the content of the pictures to reduce negative affect ('Reappraise'). Significant activations were identified using whole-brain analysis. Results: No significant group differences were seen when comparing Reappraise and Maintain conditions. However, when compared to healthy controls, depressed adolescents on placebo showed reduced visual activation to aversive pictures irrespective of the condition. The depressed adolescent group on fluoxetine showed the opposite pattern, i.e. increased visuo-cerebellar activity in response to aversive pictures, when compared to depressed adolescents on placebo. Conclusions: These data suggest that depression in adolescence may be associated with reduced visual processing of aversive imagery and that fluoxetine may act to reduce avoidance of such cues. This could reflect a key mechanism whereby depressed adolescents engage with negative cues previously avoided. Future research combining fMRI with eye-tracking is nonetheless needed to further clarify these effects. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Serotonin and Depression," by D. Healy in the April 21, 2015 issue.

There has been increasing interest in the antidepressant effects of the muscarinic cholinergic receptor antagonist scopolamine. Here we assess, for the first time, whether a transdermal scopolamine patch is sufficient to induce changes in cognition that are consistent with the reported cognitive and antidepressant effects of scopolamine. A scopolamine or placebo patch was administered to healthy volunteers ( n=33) for 17 h in a double-blind, between-subject procedure. There was no clear effect of scopolamine patch on emotional cognition, verbal or working memory, suggesting that the effective dose of scopolamine available through the patch is too low to represent a viable antidepressant mechanism. [ABSTRACT FROM AUTHOR]

Introduction: Statins have been proposed as a strategy for treating depression, but their benefit in the absence of concurrent antidepressant treatment is unclear. This meta-analysis investigated the antidepressant effects of statin monotherapy in the general population.Methods: We conducted a literature search of randomised controlled trials using any statin monotherapy versus any control condition for depressive symptoms. Our primary efficacy outcome was the mean value on any standardised scale for depression at study endpoint. We also measured efficacy at three further timepoints (<6 months, 6-12 months, >12 months), as well as acceptability, tolerability, and safety. Respectively, continuous and dichotomous outcomes were computed using standardised mean difference (SMD) or relative risk (RR) with 95% confidence intervals (CI) using a random-effect model.Results: Pooled analyses did not show that statin monotherapy improves depressive symptoms at endpoint (N = 2712 SMD = -0.18; 95% CI = -0.41 to 0.04), nor at any other specific timepoint. No difference between statins and control was identified for any of the other outcome measures.Discussion: These results differ from those of previous meta-analyses and, compounded by more recently available evidence, suggest that statins may not have intrinsic antidepressant properties, but may be useful for the management of depression in add-on to antidepressants.Limitations: Data from heterogeneous populations and using different statins were pooled, though several sensitivity and subgroup analyses were performed to account for that. PROSPERO registration: CRD42022306653. https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=306653. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rationale: Bright light treatment (BLT) is an efficacious antidepressant intervention, but its mechanism of action is not well understood. Antidepressant drugs acutely affect how emotional information is processed, pushing the brain to prioritise positive relative to negative input. Whether BLT could have a similar effect is not known to date. Objective: To test whether BLT acutely influences emotional information processing similar to antidepressant drugs, using an established healthy volunteer assay. Methods: Following a double-blind, parallel-group design, 49 healthy volunteers (18–65 years, 26 females) were randomly allocated to 60-min BLT (≥ 10,000 lux) or sham-placebo treatment early in the morning in autumn/winter. Immediately after treatment, emotional information processing was assessed using the Oxford Emotional Test Battery, a validated set of behavioural tasks tapping into emotional information processing in different cognitive domains. Participants also completed questionnaires before and after treatment to assess changes in subjective state. Results: The BLT group did not show significantly more positively biased emotional information processing compared to the placebo group (p > 0.05 for all measures). After adjustment for pre-treatment scores, there were also no significant post-treatment differences between groups in subjective state (p > 0.05 for all measures). Conclusions: BLT did not show immediate effects on emotional information processing in an established healthy volunteer assay. Thus, BLT might exert its clinical effects through a different (cognitive) mechanism than other antidepressant interventions. Future studies should corroborate this finding including clinical populations and more intensive treatment regimes, and control for potential chronobiological effects. [ABSTRACT FROM AUTHOR]

Background: Growing evidence from clinical trials and epidemiological studies suggests that statins can have clinically significant antidepressant effects, potentially related to anti-inflammatory action on several neurobiological structures. However, the underlying neuropsychological mechanisms of these effects remain unexplored. Aims: In this experimental medicine trial, we investigated the 7-day effects of the lipophilic statin, atorvastatin on a battery of neuropsychological tests and inflammation in healthy volunteers. Methods: Fifty healthy volunteers were randomised to either 7 days of atorvastatin 20 mg or placebo in a double-blind design. Participants were assessed with psychological questionnaires and a battery of well-validated behavioural tasks assessing emotional processing, which is sensitive to putative antidepressant effects, reward learning and verbal memory, as well as the inflammatory marker, C-reactive protein. Results: Compared to placebo, 7-day atorvastatin increased the recognition (p = 0.006), discriminability (p = 0.03) and misclassifications (p = 0.04) of fearful facial expression, independently from subjective states of mood and anxiety, and C-reactive protein levels. Otherwise, atorvastatin did not significantly affect any other psychological and behavioural measure, nor peripheral C-reactive protein. Conclusions: Our results reveal for the first time the early influence of atorvastatin on emotional cognition by increasing the processing of anxiety-related stimuli (i.e. increased recognition, discriminability and misclassifications of fearful facial expression) in healthy volunteers, in the absence of more general effects on negative affective bias. Further studies exploring the effects of statins in depressed patients, especially with raised inflammatory markers, may clarify this finding and inform future clinical trials. [ABSTRACT FROM AUTHOR]

Animal experimental studies suggest that 5-HT4 receptor activation holds promise as a novel target for the treatment of depression and cognitive impairment. 5-HT4 receptors are post-synaptic receptors that are located in striatal and limbic areas known to be involved in cognition and mood. Consistent with this, 5-HT4 receptor agonists produce rapid antidepressant effects in a number of animal models of depression, and pro-cognitive effects in tasks of learning and memory. These effects are accompanied by molecular changes, such as the increased expression of neuroplasticity-related proteins that are typical of clinically useful antidepressant drugs. Intriguingly, these antidepressant-like effects have a fast onset of their action, raising the possibility that 5-HT4 receptor agonists may be a particularly useful augmentation strategy in the early stages of SSRI treatment. Until recently, the translation of these effects to humans has been challenging. Here, we review the evidence from animal studies that the 5-HT4 receptor is a promising target for the treatment of depression and cognitive disorders, and outline a potential pathway for the efficient and cost-effective translation of these effects into humans and, ultimately, to the clinic. [ABSTRACT FROM AUTHOR]

Background: 5-HT4 receptor stimulation has pro-cognitive and antidepressant-like effects in animal experimental studies; however, this pharmacological approach has not yet been tested in humans. Here we used the 5-HT4 receptor partial agonist prucalopride to assess the translatability of these effects and characterise, for the first time, the consequences of 5-HT4 receptor activation on human cognition and emotion. Methods: Forty one healthy volunteers were randomised, double-blind, to a single dose of prucalopride (1 mg) or placebo in a parallel group design. They completed a battery of cognitive tests measuring learning and memory, emotional processing and reward sensitivity. Results: Prucalopride increased recall of words in a verbal learning task, increased the accuracy of recall and recognition of words in an incidental emotional memory task and increased the probability of choosing a symbol associated with a high likelihood of reward or absence of loss in a probabilistic instrumental learning task. Thus acute prucalopride produced pro-cognitive effects in healthy volunteers across three separate tasks. Conclusions: These findings are a translation of the memory enhancing effects of 5-HT4 receptor agonism seen in animal studies, and lend weight to the idea that the 5-HT4 receptor could be an innovative target for the treatment of cognitive deficits associated with depression and other neuropsychiatric disorders. Contrary to the effects reported in animal models, prucalopride did not reveal an antidepressant profile in human measures of emotional processing. [ABSTRACT FROM AUTHOR]

• The severity of childhood trauma experience contributes to lack of response to antidepressant treatment. • Untreated depressed patients show increased diurnal cortisol levels compared with those on antidepressant medication both treatment responder and non-responder patients. • The severity of childhood trauma contributes to increased HPA axis activity and higher cortisol production specifically in depressed patients who present glucocorticoid resistance. • Glucocorticoid resistance may be a novel target for development of personalised treatment for a subgroup of depressed patients with a history of childhood trauma. Childhood trauma is among the most potent contributing risk factors for depression and is associated with poor treatment response. Hypothalamic-pituitary-adrenal (HPA) axis abnormalities have been linked to both childhood trauma and depression, but the underlying mechanisms are poorly understood. The present study aimed to investigate the link between childhood trauma, HPA axis activity and antidepressant response in patients with depression. As part of the Wellcome Trust NIMA consortium, 163 depressed patients and 55 healthy volunteers were included in this study. Adult patients meeting Structured Clinical Interview for Diagnostic and Statistical Manual Version-5 criteria for major depression were categorised into subgroups of treatment responder (n = 42), treatment non-responder (n = 80) and untreated depressed (n = 41) based on current depressive symptom severity measured by the 17-item Hamilton Rating Scale for Depression and exposure to antidepressant medications established by Antidepressant Treatment Response Questionnaire. Childhood Trauma Questionnaire was obtained. Baseline serum C-reactive protein was measured using turbidimetric detection. Salivary cortisol was analyzed at multiple time points during the day using the ELISA technique. Glucocorticoid resistance was defined as the coexistence of hypercortisolemia and inflammation. Our results show that treatment non-responder patients had higher exposure to childhood trauma than responders. No specific HPA axis abnormalities were found in treatment non-responder depressed patients. Untreated depressed showed increased diurnal cortisol levels compared with patients on antidepressant medication, and higher prevalence of glucocorticoid resistance than medicated patients and controls. The severity of childhood trauma was associated with increased diurnal cortisol levels only in individuals with glucocorticoid resistance. Therefore, our findings suggest that the severity of childhood trauma experience contributes to a lack of response to antidepressant treatment. The effects of childhood trauma on increased cortisol levels are specifically evident in patients with glucocorticoid resistance and suggest glucocorticoid resistance as a target for the development of personalized treatment for a subgroup of depressed patients with a history of childhood trauma rather than for all patients with resistance to antidepressant treatment. [ABSTRACT FROM AUTHOR]

Controversy continues with regard to antidepressants and withdrawal. Recent debates have focused on the prevalence and length of withdrawal, and some continue to state that withdrawal from these compounds constitutes 'addiction'. In this editorial we examine the evidence underlying these recent debates. We acknowledge gaps in knowledge, and make suggestions for how the field can progress. [ABSTRACT FROM AUTHOR]

The timely selection of the optimal treatment for depressed patients is critical to improve remission rates. The detection of pre-treatment variables able to predict differential treatment response may provide novel approaches for treatment selection. Selective serotonin reuptake inhibitors (SSRIs) modulate the fronto-limbic functional response and connectivity, an effect preceding the overt clinical antidepressant effects. Here we investigated whether the cortico-limbic connectivity associated with emotional bias measured before SSRI administration predicts the efficacy of antidepressant treatment in MDD patients. fMRI and Dynamic Causal Modeling (DCM) were combined to study if effective connectivity might differentiate healthy controls (HC) and patients affected by major depression who later responded (RMDD, n =21), or failed to respond (nRMDD, n =12), to 6 weeks of escitalopram administration. Sixteen DCMs exploring connectivity between anterior cingulate cortex (ACC), ventrolateral prefrontal cortex (VLPFC), Amygdala (Amy), and fusiform gyrus (FG) were constructed. Analyses revealed that nRMDD had reduced endogenous connectivity from Amy to VLPFC and to ACC, with an increased connectivity and modulation of the ACC to Amy connectivity when processing of fearful emotional stimuli compared to HC. RMDD and HC did not significantly differ among themselves. Pre-treatment effective connectivity in fronto-limbic circuitry could be an important factor affecting antidepressant response, and highlight the mechanisms which may be involved in recovery from depression. These results suggest that fronto-limbic connectivity might provide a neural biomarker to predict the clinical outcome to SSRIs administration in major depression. [ABSTRACT FROM AUTHOR]

The antidepressant, agomelatine, has a novel pharmacological profile, with agonist properties at M1 and M2 receptors and antagonist properties at 5HT2C receptors. Whether the antidepressant effects of this treatment are mediated by the drug's effects at the M1 and M2 receptors or the 5HT2C receptor or a synergy between these actions remains unclear. In the present study, a healthy volunteer model of emotional processing, which discriminates between effective and non-effective antidepressant compounds, was used to assess the contribution of melatonin agonism to the efficacy of agomelatine. Fifty-eight healthy volunteers were randomised to receive 7 days of once daily treatment with either 1 mg melatonin, 3 mg melatonin or placebo. Seven days treatment with 3 mg melatonin resulted in earlier bedtimes consistent with a phase advance in circadian rhythm. Some marginal effects of melatonin were observed on emotional processing; however, these were neither consistent with nor comparable to those seen following conventional antidepressant treatment or with agomelatine itself. These data suggest that the antidepressant action of agomelatine cannot be accounted for solely by its action at the M1 and M2 receptors. [ABSTRACT FROM AUTHOR]

Treatment with the dopamine D2/D3 receptor agonist pramipexole has demonstrated promising clinical effects in patients with depression. However, the mechanisms through which pramipexole might alleviate depressive symptoms are currently not well understood. Conventional antidepressant drugs are thought to work by biasing the processing of emotional information in favour of positive relative to negative appraisal. In this study, we used an established experimental medicine assay to explore whether pramipexole treatment might have a similar effect. Employing a double-blind, parallel-group design, 40 healthy volunteers (aged 18 to 43 years, 50% female) were randomly allocated to 12 to 15 days of treatment with either pramipexole (at a peak daily dose of 1.0 mg pramipexole salt) or placebo. After treatment was established, emotional information processing was assessed on the neural level by measuring amygdala activity in response to positive and negative facial emotional expressions, using functional magnetic resonance imaging (MRI). In addition, behavioural measures of emotional information processing were collected at baseline and on drug, using an established computerized task battery, tapping into different cognitive domains. As predicted, pramipexole-treated participants, compared to those receiving placebo, showed decreased neural activity in response to negative (fearful) vs. positive (happy) facial expressions in bilateral amygdala. Contrary to our predictions, however, pramipexole treatment had no significant antidepressant-like effect on behavioural measures of emotional processing. This study provides the first experimental evidence that subacute pramipexole treatment in healthy volunteers modifies neural responses to emotional information in a manner that resembles the effects of conventional antidepressant drugs. [ABSTRACT FROM AUTHOR]