Really? What about all this research?
Stomach–brain synchronisation is associated with poorer mental health
Edwin S. Dalmaijer edwin.dalmaijer@bristol.ac.uk Affiliations & Notes Show Outline
Abstract
In common parlance, ‘being in touch with your body’ is often used positively. However, in a recent study, Banellis, Rebollo, and colleagues show that better stomach–brain synchronisation is actually associated with increased anxiety and depression scores. These findings add an interesting dimension to debates on the role of interoception in mental health.Keywords
Main text The brain is intimately connected to the rest of the body to maintain homeostasis. It can be figuratively described as conducting the visceral orchestra. Key to this process is interoception: monitoring and actively predicting internal physiological signals [1]. For over a century, researchers have centred these peripheral signals in theories of emotion and, more recently, as a contributor to mental health [2]. New insights into the mechanism behind this link are presented in a recent publication by Banellis, Rebollo,et al., who found that increased synchronisation between brain and stomach was associated with poorer mental health [3]. While traditional (ex vivo) anatomical work has identified connections between brain and stomach, more recently, the combination of electrogastrography and functional magnetic resonance imaging has been used to study the gastric network in living human brains [4]. This approach allows for identifying the sequence of brain areas that covary with the slow (0.05 Hz) normogastric rhythm of the stomach. Using this approach, Banellis, Rebollo, et al. mapped the neurogastric synchrony of 243 participants. They also mapped participants’ psychological profile using a battery of mental health and lifestyle questionnaires. These data are challenging to analyse due to their high dimensionality and the likely tendency for variables to covary more strongly within each data modality. An elegant solution was found in canonical correlation analysis, which identifies pairs of highly correlated canonical variates across data modalities. The result was a single pair in which the stomach–brain variate loaded negatively on posterior frontal and parietal regions, including posterior superior frontal gyrus, inferior parietal lobule, and posterior intraparietal sulcus. Higher scores on this variate thus meant lower stomach–brain synchrony. The psychological variate loaded negatively onto symptoms of anxiety, depression, stress, fatigue, and a variety of other markers of poor mental health, and positively on wellbeing and quality of life scores. Higher scores on this variate thus meant better mental health. Because the variates are correlated, the results showed that higher general mental health was associated with lower stomach–brain connectivity.Banellis, Rebollo,et al. carefully avoided causal claims, as it remains unclear whether higher neurogastric connectivity was cause, consequence, or only consonant with poorer mental health. Nevertheless, the direction of the association is surprising: it goes against the common idea that ‘more’ interoception (‘listening to your body’) should be better for mental health. This contrast, however, is only superficial. Healthy interoception is adaptive and aligned with the state of the body [2], and increased neurogastric coupling could reflect increased monitoring of the stomach for the wrong reasons.The idea of context-dependent interoception is echoed in the interpretation of somatic signals. Recent studies in this field have found no direct associations between pain characteristics and anxiety or depression symptoms in people with chronic pain [5], nor between mental health scores and lab-assessed pain sensitivity in a community sample [6]. However, those who thought of their body as an adversary were less willing to experience pain or to engage in valued daily activities and they showed higher anxiety scores [5]. In addition, the self-reported experience of somatic symptoms (including gastrointestinal discomfort) did correlate strongly with depression scores [6]. Thus, mental health does not appear to be associated with objective sensitivity to internal signals, but rather their subjective experience or interpretation.
In the study by Banellis, Rebollo, et al. [3], the relationship between mental health and neurogastric coupling was found to be selective, in the sense that no associations with cardiac rhythms were found. This is noteworthy, because specific aberrations of stomach rhythms (collectively referred to as ‘proto-nausea’) are associated with the experience of disgust [7]. This is of transdiagnostic relevance, as disgust is a risk and maintenance factor in conditions such as eating disorders [8], obsessive compulsive disorder, and specific phobias [9]. Disgust renders current therapeutic tools less effective due to its ‘cognitive impenetrability’, likely because of its close association with the stomach. Recent experimental work suggests that pharmacologically normalising stomach rhythm reduces disgust avoidance [10]. If replicated in clinical samples, this could offer a potential adjuvant to cognitive behavioural therapy.
In sum, Banellis, Rebollo, et al. found that poorer mental health was associated with better neurogastric synchronisation. This is key empirical evidence that ‘more interoception’ is not always better. Instead, the findings align with the idea that interoception is gated by attention to bodily signals, which can increase due to their negative subjective experience. These new findings also underscore the need to better understand the role of the stomach and related emotions across diagnostic categories. Perhaps the folk wisdom should be updated: ‘Listen to your body, but only if it has something useful to say’.
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