IntroductionThe prevalence of psychological disorders remains stable despite steady increases in pharmacological treatments suggesting the need for auxiliary treatment options. Consideration of the brain–gut–microbiota axis (BGMA) has made inroads into reconceptualizing psychological illness from a more holistic perspective. While our understanding of the precise role of gut microbiota (GM) in psychological illness is in its infancy, it represents an attractive target for novel interventions.MethodAn extensive review of relevant literature was undertaken.ResultsGut microbiota are proposed to directly and indirectly influence mood, cognition, and behavior which are key components of mental health. This paper outlines how GM may be implicated in psychological disorders from etiology through to treatment and prevention using the Four P model of case formulation.ConclusionMoving forward, integration of GM into the conceptualization and treatment of psychological illness will require the discipline of psychology to undergo a significant paradigm shift. While the importance of the GM in psychological well‐being must be respected, it is not proposed to be a panacea, but instead, an additional arm to a multidisciplinary approach to treatment and prevention.

There is ongoing debate on the utility of trait emotional intelligence and whether it is distinguishable from the five-factor model of personality. In study 1, we investigated the incremental validity of trait emotional intelligence in predicting negative emotional states, after controlling for the five-factor model personality traits. The TEIQue, Mini-IPIP, and DASS-21 were administered to a community based Australian sample. Three significant predictive models emerged: (1) wellbeing, and neuroticism predicting depression; (2) emotionality, and neuroticism predicting anxiety; and (3) self-control, and neuroticism predicting stress. In Study 2, we further explored the relationship between TEIQue domains, neuroticism, and negative emotional states. Three partial mediation models were found: (1) wellbeing mediated the relationship between neuroticism and depression; (2) emotionality mediated the relationship between neuroticism and anxiety; and (3) self-control mediated the relationship between neuroticism and stress. The findings highlight that trait emotional intelligence is related to, and yet distinct from extraversion, conscientiousness, agreeableness, neuroticism, and openness. They also provide support for the incremental validity of the TEIQue domains in predicting depression, anxiety, and stress, beyond the five-factor model personality traits in a community based Australian sample, with the domains of trait emotional intelligence potentially operating as protective factors from pervasive negative moods.

Background Research into the brain-gut-microbiota axis (BGMA) continues to reveal associations between gut microbiota (GM) and psychological symptom expression, inspiring new ways of conceptualising psychological disorders. However, before GM modulation can be touted as a possible auxiliary treatment option, more research is needed as inconsistencies in previous findings regarding these associations are prevalent. Additionally, the concept of the microgenderome, which proposes that GM may interact with sex hormones, has received limited attention in studies using human samples to date. However, such research has demonstrated sex specific associations between GM and psychological symptom expression. Method This cross-sectional retrospective study explores associations between GM species (identified through faecal microbial analysis) and symptom severity across four psychological domains (Depressive, Neurocognitive, Stress and Anxiety, and Sleep and Fatigue) for males (N = 1143) and females (N = 3467) separately. Results GM species from several genera including Bifidobacterium, Clostridium, Enterococcus, and Leuconostoc were found to be differentially associated with psychological symptom severity for males and females. As such, the findings of the current study provide support for the concept of the microgenderome. Conclusion While further research is needed before their implementation in psychological treatment plans, the current findings suggest that modulation of GM at the species level may hold promise as auxiliary diagnostic or treatment options. These findings may give further insight into a client’s presenting problem from a more holistic, multidisciplinary perspective. The clear sex divergence in associations between GM and symptoms give insight into sex discrepancies in susceptibility to psychological disorders.

Health outcomes associated with Blastocystis sp. and Dientamoeba fragilis are disparate and controversial, ranging from health benefits, to years of asymptomatic carriage, through to severe illness. Evidence that Blastocystis sp. and D. fragilis are commensal members of the gut microbiota is growing. Despite this, little to no research exists investigating the potential effect of these protozoa on psychological symptom expression. As such, the aim of this retrospective cross-sectional study was to be the first to investigate the effect of protozoan carriage on severity of Depressive, Neurocognitive, Stress and Anxiety, and Sleep and Fatigue symptoms, and whether this effect changes as a function of sex. The prevalence of D. fragilis was significantly higher in females compared to males, however there were no sex differences in prevalence for Blastocystis sp. (data used in the current study contained ST1, ST3, and Blastocystis ST unspecified) or co-carriage of the two. Females reported significantly more severe symptoms across all four psychological domains compared to males. There was no significant interaction between sex and Blastocystis sp. carriage on psychological symptom severity, and no significant main effect of Blastocystis sp. on symptom severity compared to those who tested negative for protozoa. When investigating the sexes separately, there was no effect of protozoan carriage on psychological symptom expression in either males or females. These findings add weight to the argument that Blastocystis sp. and D. fragilis are not necessarily pathogenic and are likely to be part of a diverse gut (which is typically associated with better health outcomes). Further research is required given that protozoan members of the gut microbiota have been largely ignored in brain-gut-microbiota axis research.