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.

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.

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.

Antidepressants have been proposed to act via their influence on emotional processing. We investigated the effect of discontinuing maintenance antidepressant treatment on positive and negative self-referential recall and the association between self-referential recall and risk of relapse.

The ANTLER trial was a large (N = 478) pragmatic double-blind trial investigating the clinical effectiveness of long-term antidepressant treatment for preventing relapse in primary care patients. Participants were randomised to continue their maintenance antidepressants or discontinue via a taper to placebo. We analysed memory for positive and negative personality descriptors, assessed at baseline, 12- and 52-week follow-up.

The recall task was completed by 437 participants. There was no evidence of an effect of discontinuation on self-referential recall at 12 [positive recall ratio 1.00, 95% CI (0.90–1.11), p = 0.93; negative recall ratio 1.00 (0.87–1.14), p = 0.87] or 52 weeks [positive recall ratio 1.03 (0.91–1.17), p = 0.62; negative recall ratio 1.00 (0.86–1.15), p = 0.96; ratios larger than one indicate higher recall in the discontinuation group], and no evidence of an association between recall at baseline or 12 weeks and later relapse [baseline, positive hazard ratio (HR) 1.02 (0.93–1.12), p = 0.74; negative HR 1.01 (0.90–1.13), p = 0.87; 12 weeks, positive HR 0.99 (0.89–1.09), p = 0.81; negative HR 0.98 (0.84–1.14), p = 0.78; ratios larger than one indicate a higher frequency of relapse in those with higher recall].

We found no evidence that discontinuing long-term antidepressants altered self-referential recall or that self-referential recall was associated with risk of relapse. These findings suggest that self-referential recall is not a neuropsychological marker of antidepressant action.

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.

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 (#NCT 04137367).

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

The COVID-19 pandemic highlighted the need for mental health interventions that can be easily disseminated during a crisis. Behavioural activation (BA) is a cost-effective treatment that can be administered by non-specialists; however, it is unclear whether it is still effective during a time of lockdown and social distancing, when opportunities for positive activity are significantly constrained.

Between May and October 2020, we randomised 68 UK participants with mild to moderate low mood to either a 4-week online programme of non-specialist administered BA or to a passive control group. Before and after the intervention, we collected self-report data on mood and COVID-related disruption, as well as measuring emotional cognition as an objective marker of risk for depression.

In comparison to the control group, the BA group showed a significant decrease in depression, anxiety and anhedonia after the intervention, as well as an increase in self-reported activation and social support. Benefits persisted at 1-month follow-up. BA also decreased negative affective bias on several measures of the Facial Emotion Recognition Task and early change in bias was associated with later therapeutic gain. Participants rated the intervention as highly acceptable.

This study highlights the benefits of online BA that can be administered by non-specialists after brief training. These findings can help inform the policy response towards the rising incidence of mental health problems during a crisis situation such as a pandemic. They also highlight the use of objective cognitive markers of risk across different treatment modalities.

According to the cognitive neuropsychological model, antidepressants reduce symptoms of depression and anxiety by increasing positive relative to negative information processing. Most studies of whether antidepressants alter emotional processing use small samples of healthy individuals, which lead to low statistical power and selection bias and are difficult to generalise to clinical practice. We tested whether the selective serotonin reuptake inhibitor (SSRI) sertraline altered recall of positive and negative information in a large randomised controlled trial (RCT) of patients with depressive symptoms recruited from primary care.

The PANDA trial was a pragmatic multicentre double-blind RCT comparing sertraline with placebo. Memory for personality descriptors was tested at baseline and 2 and 6 weeks after randomisation using a computerised emotional categorisation task followed by a free recall. We measured the number of positive and negative words correctly recalled (hits). Poisson mixed models were used to analyse longitudinal associations between treatment allocation and hits.

A total of 576 participants (88% of those randomised) completed the recall task at 2 and 6 weeks. We found no evidence that positive or negative hits differed according to treatment allocation at 2 or 6 weeks (adjusted positive hits ratio = 0.97, 95% CI 0.90–1.05, p = 0.52; adjusted negative hits ratio = 0.99, 95% CI 0.90–1.08, p = 0.76).

In the largest individual placebo-controlled trial of an antidepressant not funded by the pharmaceutical industry, we found no evidence that sertraline altered positive or negative recall early in treatment. These findings challenge some assumptions of the cognitive neuropsychological model of antidepressant action.

Depression is characterised by negative views of the self. Antidepressant treatment may remediate negative self-schema through increasing processing of positive information about the self. Changes in affective processing during social interactions may increase expression of prosocial behaviours, improving interpersonal communications.

To examine whether acute administration of citalopram is associated with an increase in positive affective learning biases about the self and prosocial behaviour.

Healthy volunteers (n = 41) were randomised to either an acute 20 mg dose of citalopram or matched placebo in a between-subjects double-blind design. Participants completed computer-based cognitive tasks designed to measure referential affective processing, social cognition and expression of prosocial behaviours.

Participants administered citalopram made more cooperative choices than those administered placebo in a prisoner's dilemma task (β = 20%, 95% CI: 2%, 37%). Exploratory analyses indicated that participants administered citalopram showed a positive bias when learning social evaluations about a friend (β = 4.06, 95% CI: 0.88, 7.24), but not about the self or a stranger. Similarly, exploratory analyses found evidence of increased recall of positive words and reduced recall of negative words about others (β = 2.41, 95% CI: 0.89, 3.93), but not the self, in the citalopram group.

Participants administered citalopram showed greater prosocial behaviours, increased positive recall and increased positive learning of social evaluations towards others. The increase in positive affective bias and prosocial behaviours towards others may, at least partially, be a mechanism of antidepressant effect. However, we found no evidence that citalopram influenced self-referential processing.

Studies suggest that d-cycloserine (DCS) may have antidepressant potential through its interaction with the glycine site of the N-methyl-D-aspartate receptor; however, clinical evidence of DCS's efficacy as a treatment for depression is limited. Other evidence suggests that DCS affects emotional learning which may also be relevant for the treatment of depression and anxiety. The aim of the present investigation was to assess the effect of DCS on emotional processing in healthy volunteers and to further characterise its effects on emotional and autobiographical memory.

Forty healthy volunteers were randomly allocated to a single dose of 250 mg DCS or placebo in a double-blind design. Three hours later, participants performed an Emotional Test Battery [including Facial Expression Recognition Task (FERT), Emotional Categorisation Task (ECAT), Emotional Recall Task (EREC), Facial Dot-Probe Task (FDOT) and Emotional Recognition Memory Task (EMEM)] and an Autobiographical Memory Test (AMT). Also, participants performed the FERT, EREC and AMT tasks again after 24 h in order to assess longer lasting effects of a single dose of DCS.

DCS did not significantly affect the FERT, EMEM and FDOT performance but significantly increased emotional memory and classification for positive words v. negative words. Also, DCS enhanced the retrieval of more specific autobiographical memories, and this effect persisted at 24 h.

These findings support the suggestion that low-dose DCS increases specific autobiographical memory retrieval and positive emotional memory. Such effects make it an intriguing agent for further investigation in clinical depression, which is characterised by decreased autobiographical memory specificity and increased negative bias in memory recall. It also underscores the potential role of DCS as an adjunct to cognitive behavioural therapy in depression.

There is demand for new, effective and scalable treatments for depression, and development of new forms of cognitive bias modification (CBM) of negative emotional processing biases has been suggested as possible interventions to meet this need.

We report two double blind RCTs, in which volunteers with high levels of depressive symptoms (Beck Depression Inventory ii (BDI-ii) > 14) completed a brief course of emotion recognition training (a novel form of CBM using faces) or sham training. In Study 1 (N = 36), participants completed a post-training emotion recognition task whilst undergoing functional magnetic resonance imaging to investigate neural correlates of CBM. In Study 2 (N = 190), measures of mood were assessed post-training, and at 2-week and 6-week follow-up.

In both studies, CBM resulted in an initial change in emotion recognition bias, which (in Study 2) persisted for 6 weeks after the end of training. In Study 1, CBM resulted in increases neural activation to happy faces, with this effect driven by an increase in neural activity in the medial prefrontal cortex and bilateral amygdala. In Study 2, CBM did not lead to a reduction in depressive symptoms on the BDI-ii, or on related measures of mood, motivation and persistence, or depressive interpretation bias at either 2 or 6-week follow-ups.

CBM of emotion recognition has effects on neural activity that are similar in some respects to those induced by Selective Serotonin Reuptake Inhibitors (SSRI) administration (Study 1), but we find no evidence that this had any later effect on self-reported mood in an analogue sample of non-clinical volunteers with low mood (Study 2).

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.

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.

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.

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.

Patients with bipolar disorder (BD) experience persistent impairments in both affective and non-affective cognitive function, which is associated with a worse course of illness and poor functional outcomes. Nevertheless, the temporal progression of cognitive dysfunction in BD remains unclear and the identification of objective endophenotypes can inform the aetiology of BD.

The present study is a cross-sectional investigation of cognitive baseline data from the longitudinal Bipolar Illness Onset-study. One hundred seventy-two remitted patients newly diagnosed with BD, 52 of their unaffected relatives (UR), and 110 healthy controls (HC) were compared on a large battery of behavioural cognitive tasks tapping into non-affective (i.e. neurocognitive) and affective (i.e. emotion processing and regulation) cognition.

Relative to HCs, patients with BD exhibited global neurocognitive deficits (ps < 0.001), as well as aberrant emotion processing and regulation (ps ⩽ 0.011); including decreased emotional reactivity to positive social scenarios, impaired ability to down-regulate positive emotion, as well as a specific deficit in the ability to recognise surprised facial expressions. Their URs also showed a trend towards difficulties identifying surprised faces (p = 0.075). No other differences in cognitive function were found for URs compared to HCs.

Neurocognitive deficits and impairments within emotion processing and regulation may be illness-related deficits of BD that present after illness-onset, whereas processing of emotional faces may represent an early risk marker of BD. However, longitudinal studies are needed to examine the association between cognitive impairments and illness progression in BD.

The neuropharmacological actions of antidepressants are well characterised but our understanding of how these changes translate into improved mood are still emerging.

To investigate whether actions of antidepressant drugs on emotional processing are a mediating factor in the effects of these drugs in depression.

We examined key published findings that explored the effects of antidepressants on behavioural and functional magnetic resonance imaging (fMRI) measures of emotional processing.

Negative emotional bias has been reliably associated with depression. Converging results suggest that antidepressants modulate emotional processing and increase positive emotional processing much earlier than effects on mood. These changes in emotional processing are associated with neural modulation in limbic and prefrontal circuitry.

Antidepressants may work in a manner consistent with cognitive theories of depression. Antidepressants do not act as direct mood enhancers but rather change the relative balance of positive to negative emotional processing, providing a platform for subsequent cognitive and psychological reconsolidation.

Selective serotonin reuptake inhibitors (SSRIs) are typically thought to have a delay of several weeks in the onset of their clinical effects. However, recent reports suggest they may have a much earlier therapeutic onset. A reduction in amygdala responsivity has been implicated in the therapeutic action of SSRIs.

To investigate the effect of a single dose of an SSRI on the amygdala response to emotional faces.

Twenty-six healthy volunteers were randomised to receive a single oral dose of citalopram (20 mg) or placebo. Effects on the processing of facial expressions were assessed 3 h later using functional magnetic resonance imaging.

Volunteers treated with citalopram displayed a significantly reduced amygdala response to fearful facial expressions compared with placebo.

Such an immediate effect of an SSRI on amygdala responses to threat supports the idea that antidepressants have an earlier onset of therapeutically relevant effects than conventionally thought.

Depression is associated with neural abnormalities in emotional processing.

This study explored whether these abnormalities underlie risk for depression.

We compared the neural responses of volunteers who were at high and low-risk for the development of depression (by virtue of high and low neuroticism scores; high-N group and low-N group respectively) during the presentation of fearful and happy faces using functional magnetic resonance imaging (fMRI).

The high-N group demonstrated linear increases in response in the right fusiform gyrus and left middle temporal gyrus to expressions of increasing fear, whereas the low-N group demonstrated the opposite effect. The high-N group also displayed greater responses in the right amygdala, cerebellum, left middle frontal and bilateral parietal gyri to medium levels of fearful v. happy expressions.

Risk for depression is associated with enhanced neural responses to fearful facial expressions similar to those observed in acute depression.

We previously found that children of parents with depression showed impaired performance on a task of emotional categorisation.

To test the hypothesis that children of parents with depression would show abnormal neural responses in the anterior cingulate cortex, a brain region involved in the integration of emotional and cognitive information.

Eighteen young people (mean age 19.8 years) with no personal history of depression but with a biological parent with a history of major depression (FH+ participants) and 16 controls (mean age 19.9 years) underwent functional magnetic resonance imaging while completing an emotional counting Stroop task.

Controls showed significant activation in the pregenual anterior cingulate cortex to both positive and negative words during the emotional Stroop task. This activation was absent in FH+ participants.

Our findings show that people at increased familial risk of depression demonstrate impaired modulation of the anterior cingulate cortex in response to emotionally valenced stimuli.

Cognitive theories associate depression with negative biases in information processing. Although negatively biased cognitions are well documented in depressed patients and to some extent in recovered patients, it remains unclear whether these abnormalities are present before the first depressive episode.

High neuroticism (N) is a well-recognized risk factor for depression. The current study therefore compared different aspects of emotional processing in 33 high-N never-depressed and 32 low-N matched volunteers. Awakening salivary cortisol, which is often elevated in severely depressed patients, was measured to explore the neurobiological substrate of neuroticism.

High-N volunteers showed increased processing of negative and/or decreased processing of positive information in emotional categorization and memory, facial expression recognition and emotion-potentiated startle (EPS), in the absence of global memory or executive deficits. By contrast, there was no evidence for effects of neuroticism on attentional bias (as measured with the dot-probe task), over-general autobiographical memory, or awakening cortisol levels.

These results suggest that certain negative processing biases precede depression rather than arising as a result of depressive experience per se and as such could in part mediate the vulnerability of high-N subjects to depression. Longitudinal studies are required to confirm that such cognitive vulnerabilities predict subsequent depression in individual subjects.