Background Research has revealed associations between microbes of the gastrointestinal tract and stress, anxiety and depression in pregnant or postpartum women. While these studies suggest a gut-brain-behaviour axis, no studies have examined microbes of the oral cavity in relation to maternal mental health. Objective To explore a potential oral-brain-behaviour axis related to maternal mental health. Methods Microbes were measured in saliva obtained from 224 second-trimester (mean±SD = 17±2 weeks) women oversampled for stress. Oralome data were associated with women’s recent or cumulative pregnancy stress, trait and state anxiety, depression symptoms and post-traumatic stress disorder (PTSD) symptoms. Covariates explored included age, income, alcohol and tobacco use, dental issues and physical health problems. Results Pregnant women in the high trait anxiety or depression symptom groups had higher oral alpha diversity, indicating higher richness of species within samples. Groups with hi

Background Cannabis use during adolescence and young adulthood has been associated with brain harm, yet despite a rapid increase in cannabis use among older adults in the past decade, the impact on brain health in this population remains understudied. Objective To explore observational and genetic associations between cannabis use and brain structure and function. Methods We examined 3641 lifetime cannabis users (mean (SD) age 61.0 (7.1) years) and 12 255 controls (mean (SD) age 64.5 (7.5) years) from UK Biobank. Brain structure and functional connectivity were measured using multiple imaging-derived phenotypes. Associations with cannabis use were assessed using multiple linear regression controlling for potential confounds. Bidirectional two-sample Mendelian randomisation analyses were used to investigate potential causal relationships. Findings Cannabis use was associated with multiple measures of brain structure and function. Participants with a history of cannabis use had poorer wh