Gut-brain axis: Study uncovers microbiota differences in impulsive and non-impulsive female convicts

A study comparing impulsively violent female convicts with age-matched non-impulsive female convicts identified four groups of bacterial species with differing abundances between the two groups. Genera Bacteroides, Barnesiella, and the order Rhodospirillales were more abundant in impulsive women, while bacteria from the genus Catenisphaera were more abundant in non-impulsive women. The research was published in Neuropsychobiology.

Impulsivity refers to the tendency to act quickly without considering the consequences, often driven by immediate desires or emotions. Impulsive individuals struggle with self-control and are prone to behaviors such as interrupting others, making hasty decisions, or engaging in risky activities. While some degree of impulsivity is normal, excessive impulsivity is linked to various mental health conditions, including ADHD, substance use disorders, criminal behavior, and suicide.

The neurotransmitters dopamine and serotonin play critical roles in impulsive behavior. Neurons that use these neurotransmitters are prominent in brain regions associated with impulse control regulation. These regions include the prefrontal cortex, amygdala, ventral tegmental area, substantia nigra, nucleus accumbens, and hippocampus. Previous research has indicated that dysregulated serotonin and dopamine activity contributes to impulsivity.

Study authors Michaela Langmajerová and Janet Ježková sought to explore whether gut microbiome composition might be associated with individual differences in impulsivity. They investigated differences in gut microbiome composition between impulsive, violent female convicts and non-impulsive, non-violent female convicts.

Scientists have relatively recently discovered the existence of a bidirectional pathway linking the brain with bacteria living in the human gut. This pathway, known as the microbiota-gut-brain axis, suggests that gut microbes can influence critical processes in the body, including human behavior. The study authors hypothesized that the composition of the gut microbiome and its metabolites might also influence the cognitive regulation of behavior.

The study participants were female convicts recruited from the Opava Prison and Forensic Detention Facility in the Czech Republic. Thirty-three of the participants had impulse control issues (i.e., they were impulsive and violent), while 20 were non-impulsive and non-violent.

Participants provided blood and stool samples. Blood samples were analyzed to determine neurotransmitter levels, while stool samples were analyzed to identify the composition of the participants’ gut microbiota and the levels of short-chain fatty acids, which are important metabolites produced by gut microbes.

The results revealed no significant differences between the two groups (impulsive and non-impulsive) in the overall diversity of their gut microbiota. However, there were differences in the relative abundances of four bacterial groups. Genera Bacteroides, Barnesiella, and the order Rhodospirillales were more abundant in impulsive women, whereas bacteria from the genus Catenisphaera were more abundant in non-impulsive women.

“We determined four differentially abundant bacterial taxa in the stool samples of non-impulsive and impulsive women; the most interesting was the genus Bacteroides regarding its potential effect on serotonin and DA [dopamine] metabolic pathways. In addition to higher fecal tryptophan levels in impulsive women, associations between gut bacteria and their metabolites might suggest a contribution of the gut microbiome in maladaptive behaviors such as impulsive aggression,” the study authors concluded.

The study provides preliminary insights into potential links between gut microbiota composition and impulsivity. However, it is important to note that the study’s design does not allow for causal inferences. Additionally, other factors beyond impulsivity might explain the observed differences in gut microbiota composition.

The paper, “Gut Microbiome in Impulsively Violent Female Convicts,” was authored by Michaela Langmajerováa Janet Ježkováb, Jakub Kreisingerd, Jaroslav Semerád, Ivan Titov, Petra Procházková, Tomáš Cajthaml, Václav Jiřička, Jan Vevera, and Radka Roubalová.