Psychiatry - Journal Articles
Permanent URI for this collection
Browse
Recent Submissions
Item Gut–brain axis and neuropsychiatric health: recent advances(Nature Research, 2025) Doenyas, Ceymi; Clarke, Gerard; Cserjési, RenátaThe gut–brain axis, a bidirectional communication pathway, permits the central nervous system (CNS) to exert influence over gastrointestinal function in response to stress, while the gut microbiota regulates the CNS via immune, neuroendocrine, and vagal pathways. Current research highlights the importance of the gut microbiota in stress-related disorders and the need for further research into the mechanisms of gut–brain communication, with potential therapeutic implications for a wide range of health conditions. This is a challenge taken on in this Scientific Reports Collection on the Gut-Brain Axis. The gut–brain axis has significant implications for neurodegenerative, psychiatric, and metabolic disorders. Recent studies have underscored the role of the gut microbiome in conditions such as Parkinson’s disease (PD), with evidence indicating that gut dysfunction and pathological features can precede motor symptoms by decades. The use of in vivo animal models has demonstrated that preformed α-synuclein fibrils (PFFs) can travel from the gut to the brain in a dosage-dependent manner, thereby supporting the “gut-first” theory in the context of PD, a theory that is explored in this Collection using in vitro approaches. There is also evidence that the gut–brain axis plays a role in obesity and machine learning algorithms may assist in differentiating between obese and overweight individuals based on their microbiota data. There is also growing interest in the role of the gut at the interface between post-traumatic stress disorder (PTSD), sleep disturbances, and irritable bowel syndrome (IBS). The studies described in this Collection support and expand on the observations from previous preclinical and clinical investigations, while also providing essential novel insights that can drive discovery into previously unexplored avenues of brain-gut-microbiome interactions in health and disease. © The Author(s) 2025.Item The gut microbiota-immune-brain axis: Therapeutic implications(Cell Press, 2025) O'Riordan, Kenneth J.; Moloney, Gerard M.; Keane, Lily; Clarke, Gerard; Cryan, John F.; Ian's Friends Foundation; Saks-Kavanaugh Foundation; DuPont; Science Foundation Ireland; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen ForschungThe microbiota-gut-brain axis has major implications for human health including gastrointestinal physiology, brain function, and behavior. The immune system represents a key pathway of communication along this axis with the microbiome implicated in neuroinflammation in health and disease. In this review, we discuss the mechanisms as to how the gut microbiota interacts with the brain, focusing on innate and adaptive immunity that are often disrupted in gut-brain axis disorders. We also consider the implications of these observations and how they can be advanced by interdisciplinary research. Leveraging an increased understanding of how these interactions regulate immunity has the potential to usher in a new era of precision neuropsychiatric clinical interventions for psychiatric, neurodevelopmental, and neurological disorders. © 2025 The AuthorsItem More than just a number: the gut microbiota and brain function across the extremes of life(Taylor & Francis, 2024) Nuzum, Nathan D.; Deady, Clara; Kittel-Schneider, Sarah; Cryan, John F.; O'Mahony, Siobhain M.; Clarke, Gerard; Science Foundation IrelandUnderstanding the interrelationship between the gut microbiota and host physiology, although still in its relative infancy, has taken important steps forward over the past decade. In the context of brain disorders including those characterized by neurodevelopmental and neurodegenerative changes there have been important advances. However, initially research involved correlational analyses, had limited translational scope, and lacked functional assessments. Thus, largescale longitudinal clinical investigations that assess causation and underlying mechanisms via in depth analysis methods are needed. In neurodegeneration research, strong causal evidence now links the gut microbiome to Alzheimer's (AD), and Parkinson's Disease (PD), as supported by human-to-animal transplantation studies. Longitudinal interventions are being conducted in AD, PD, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis. Neurodevelopmental research has also seen a boon in microbiome-related clinical research including in autism, Attention-deficit/hyperactivity disorder, and schizophrenia, which is confirming prior animal model work regarding the key time-windows in the gut microbiome important for infant cognition. While recent research advances represent important progress, fundamental knowledge gaps and obstacles remain. Knowing how and why the gut microbiome changes at the extremes of life will develop our mechanistic understanding and help build the evidence base as we strive toward counteracting microbial missteps with precision therapeutic interventions.Item Differential cortical aspartate uptake across the oestrous cycle is associated with changes in gut microbiota in Wistar-Kyoto rats(Elsevier B.V., 2024-12-26) Sajjad, Jahangir; Morael, Jennifer; Melo, Thieza G.; Foley, Tara; Murphy, Amy; Keane, James; Popov, Jelena; Stanton, Catherine; Dinan, Timothy G.; Clarke, Gerard; Cryan, John F.; Collins, James M.; O’Mahony, Siobhain M.; Science Foundation IrelandPain and psychological stress are intricately linked, with sex differences evident in disorders associated with both systems. Glutamatergic signalling in the central nervous system is influenced by gonadal hormones via the hypothalamic–pituitary–adrenal axis and is central in pain research. Emerging evidence supports an important role for the gut microbiota in influencing pain signalling. Here, the functional activity of excitatory amino acid transporters (EAATs) in the anterior cingulate cortex (ACC) and lumbosacral spinal cord of male and female Wistar-Kyoto rats, an animal model of comorbid visceral hypersensitivity and enhanced stress responsivity, was investigated across the oestrous cycle. Correlations between the gut microbiota and changes in the functional activity of the central glutamatergic system were also investigated. EAAT function in the lumbosacral spinal cord was similar between males and females across the oestrous cycle. EAAT function was higher in the ACC of dioestrus females compared to proestrus and oestrus females. In males, aspartate uptake in the ACC positively correlated with Bacteroides, while aspartate uptake in the spinal cord positively correlated with the relative abundance of Lachnospiraceae NK4A136. Positive associations with aspartate uptake in the spinal cord were also observed for Alistipes and Bifidobacterium during oestrus, and Eubacterium coprostanoligenes during proestrus. Clostridium sensu stricto1 was negatively associated with aspartate uptake in the ACC in males and dioestrus females. These data indicate that glutamate metabolism in the ACC is oestrous stage-dependent and that short-chain fatty acid-producing bacteria are positively correlated with aspartate uptake in males and during specific oestrous stages in females.Item Occurrence and co-occurrence of hallucinations by modality in schizophrenia-spectrum disorders(Elsevier B.V., 2017-03-06) McCarthy-Jones, Simon; Smailes, David; Corvin, Aiden; Gill, Michael; Morris, Derek W.; Dinan, Timothy G.; Murphy, Kieran C.; O′Neill, F. Anthony; Waddington, John L.; Donohoe, Gary; Dudley, RobertIt is not only unclear why hallucinations in schizophrenia occur with different prevalence by modality, but also to what extent they do. Reliable prevalence estimates of hallucinations by modality in schizophrenia are currently lacking, particularly for non-auditory hallucinations. Studies have also tended to report lifetime, not point prevalence by modality. This study assessed the prevalence and co-occurrence of hallucinations, for both lifetime and point prevalence, across the auditory, visual, olfactory, and tactile modalities, in people diagnosed with chronic schizophrenia-spectrum disorders in Ireland (N=693) and Australia (N=218). Lifetime prevalence was 64–80% auditory, 23–31% visual, 9–19% tactile, and 6–10% olfactory. Past month prevalence was 23–27% auditory, 5–8% visual, 4–7% tactile, and 2% olfactory. The majority of participants had only hallucinated in one modality, with this nearly always being the auditory. Approximately one-third had hallucinated in two modalities, most commonly the auditory and visual. Most currently hallucinating patients also hallucinated in a single modality, again, nearly always the auditory. Whereas 30–37% of patients with lifetime auditory hallucinations had experienced visual hallucinations, 83–97% of patients with experience of visual hallucinations had experienced auditory hallucinations. These findings help delineate the modality distribution of hallucinations in schizophrenia, and provide an explanatory target for theoretical models.