Psychobiotics were previously defined as live bacteria (probiotics) which, when ingested, confer mental health benefits through interactions with commensal gut bacteria. We expand this definition to encompass prebiotics, which enhance the growth of beneficial gut bacteria. We review probiotic and prebiotic effects on emotional, cognitive, systemic, and neural variables relevant to health and disease. We discuss gut–brain signalling mechanisms enabling psychobiotic effects, such as metabolite production. Overall, knowledge of how the microbiome responds to exogenous influence remains limited. We tabulate several important research questions and issues, exploration of which will generate both mechanistic insights and facilitate future psychobiotic development. We suggest the definition of psychobiotics be expanded beyond probiotics and prebiotics to include other means of influencing the microbiome.

Objective To identify risk factors for fear of childbirth (FOC) according to parity and socioeconomic status, and to evaluate associations between FOC and adverse perinatal outcomes.Design A cohort study.Setting The Finnish Medical Birth Register.Population All 788 317 singleton births during 1997-2010 in Finland.Methods Fear of childbirth was defined according to the International Classification of Diseases code O99.80, and its associations with several risk factors and perinatal outcomes were analysed by multivariable logistic regression.Main outcome measures Prevalence of, risk factors for and outcomes of FOC.Results Fear of childbirth was experienced by 2.5% of nulliparous women and 4.5% of multiparous women. The strongest risk factors for FOC in nulliparous women were depression [adjusted odds ratio (aOR), 6.35; 95% confidence interval (CI), 5.25-7.68], advanced maternal age (aOR, 3.78; 95% CI, 3.23-4.42) and high or unspecified socioeconomic status. In multiparous women, the strongest risk factors for FOC were depression (aOR, 5.47; 95% CI, 4.67-6.41), previous caesarean section (CS) (aOR, 3.02; 95% CI, 2.93-3.11) and high or unspecified socioeconomic status. Among both nulliparous and multiparous women, FOC was associated with higher rates of CS (3.3-fold and 4.5-fold higher, respectively) and a lower incidence of low birthweight (<2500 g), small for gestational age babies, preterm birth and low Apgar scores at 1 minute.Conclusions High and unspecified socioeconomic status, advanced maternal age and depression are predisposing factors for FOC regardless of parity. Among multiparous women, a previous CS increases vulnerability to FOC. FOC is associated with increased rates of CS, but does not adversely affect other pregnancy outcomes.

ObjectivesTo identify risk factors for and the consequences (several adverse perinatal outcomes) of physician-diagnosed major depression during pregnancy treated in specialised healthcare.DesignA population-based cross-sectional study.SettingData were gathered from Finnish health registers for 1996–2010.ParticipantsAll singleton births (n=511 938) for 2002–2010 in Finland.Primary outcome measuresPrevalence, risk factors and consequences of major depression during pregnancy.ResultsAmong 511 938 women, 0.8% experienced major depression during pregnancy, of which 46.9% had a history of depression prior to pregnancy. After history of depression, the second strongest associated factor for major depression was fear of childbirth, with a 2.6-fold (adjusted OR (aOR=2.63, 95% CI 2.39 to 2.89) increased prevalence. The risk profile of major depression also included adolescent or advanced maternal age, low or unspecified socioeconomic status (SES), single marital status, smoking, prior pregnancy terminations, anaemia and gestational diabetes regardless of a history of depression. Outcomes of pregnancies were worse among women with major depression than without. The contribution of smoking was substantial to modest for small-for-gestational age newborn (<−2 SD below mean birth), low birth weight (<2500 g), preterm birth (<37 weeks) and admission to neonatal intensive care associated with major depression, whereas SES made only a minor contribution.ConclusionsPhysician-diagnosed major depression during pregnancy was found to be rare. The strongest risk factor was history of depression prior to pregnancy. Other associated factors were fear of childbirth, low SES, lack of social support and unhealthy reproductive behaviour such as smoking. Outcomes of pregnancies were worse among women with major depression than without. Smoking during pregnancy made a substantial to modest contribution to adverse outcomes associated with depression during pregnancy.