Rationale The gut-brain axis includes bidirectional communication between intestinal microbiota and the central nervous system. Bifidobacterium and Lactobacillus spp. have been implicated in psychological health, such as depression, through various pathways (e.g. inflammation). Research needs a better understanding of direct and indirect effects through examination of psychological factors that make people susceptible to, or offer protection against, depression. Objective This study investigated the relationships between gut microbiota, inflammation and psychological risk and resilience factors for depression. Methods Forty participants (13 m/27 f) recruited from the general population completed self-report questionnaires for depression, self-judgement, over-identification and affective and cognitive empathy. Faecal and blood samples were taken to assay microbiota ( Bifidobacterium ; Lactobacillus spp.) and pro-inflammatory molecules (C-reactive protein, CRP and interleukin-6, IL-6), respectively. Results Hierarchical regression analyses (controlling for sex, age and the shared variance of risk and resilience factors) showed that (i) cognitive depression was significantly predicted by negative self-judgement and reduced cognitive empathy; (ii) abundance of Lactobacillus spp. was directly related to positive self-judgement but only indirectly to cognitive depression and lower affective empathy (both through self-judgement); and (iii) CRP was the strongest predictor of reduced cognitive empathy, with suppression effects seen for age (negative) and IL-6 (positive) after controlling for CRP. Conclusions Findings suggest that lactobacilli and inflammation may be differentially associated with mood disorder via brain mechanisms underpinning self-judgement and cognitive empathy, respectively. Further trials investigating interventions to increase Lactobacillus spp. in depression would benefit from direct measures of self-judgement and affective empathic distress, whilst those that aim to reduce inflammation should investigate cognitive empathy. Electronic supplementary material The online version of this article (10.1007/s00213-019-05230-2) contains supplementary material, which is available to authorized users.

Schizotypy is a latent organisation of a cluster of personality styles, such as magical thinking, disorganisation and anhedonia, which are in the normal range of the psychosis continuum. Schizotypy relates to an increased likelihood of perceiving expressed emotion (EE). EE is characterised by criticism, rejection, and emotional over-involvement and less warmth from a close relative. Neuroimaging studies have found normal frontal lobe activation to EE-criticism in people with high schizotypy. Alternatively, electroencephalography measures emotion processing, such as frontal theta power and occipital alpha. Frontal theta power responds to cognitive and affective processes and occipital alpha power denotes less consciousness and emotional attention. This study aimed to determine the relation of these electroencephalography responses during criticism and praise to perceived emotional support. Participants (n=32) representing the full (low-to-high) range of positive schizotypy listened to and rated the self-relevance of EE-like criticism and praise and affectively neutral comments while undergoing electroencephalography. Participants completed self-report measures of schizotypy, depression and anxiety. A subset of those with a high positive schizotypy score (n=22) completed a measure of perceived EE-lack of emotional support. Higher perceived EE-lack of emotional support correlated with lower frontal theta power and lower occipital alpha power during criticism and praise in schizotypal participants. The findings suggest that these neural responses may relate to less perceived emotional support in people with high schizotypy, of which a reduction of frontal theta power denotes less emotional arousal and lower occipital alpha power denotes more alertness to emotional information.

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