Gut microbes associated with temperament traits in children

Summary: Study finds a correlation between early infant gut microbiota composition and temperament traits in toddlers. Positive emotionality was associated with higher Streptococcus and Bifidobacterium levels, while negative and fear reactivity was associated with reduced bacterial diversity.

Source: University of Turku

Scientists in the FinnBrain research project of the University of Turku, Finland, discovered that the gut microbes of a 2.5-month-old infant are associated with the temperament traits manifested at six months of age. Temperament describes individual differences in expressing and regulating emotions in infants, and the study provides new information on the association between behaviour and microbes. A corresponding study has never been conducted on infants so young or on the same scale.

Rodent studies have revealed that the composition of gut microbiota and its remodelling is connected to behaviour. In humans, gut microbes can be associated with different diseases, such as Parkinson’s disease, depression and autism spectrum disorders, but little research has been conducted on infants.

Doctoral Candidate, Doctor Anna Aatsinki from the FinnBrain research project at the University of Turku, Finland, discovered in her study on 303 infants that different temperament traits are connected with individual microbe genera, microbial diversity and different microbe clusters.

“It was interesting that, for example, the Bifidobacterium genus including several lactic acid bacteria was associated with higher positive emotions in infants. Positive emotionality is the tendency to experience and express happiness and delight, and it can also be a sign of an extrovert personality later in life,” says Aatsinki.

Temperament Can Predict Later Development

One of the findings was that greater diversity in gut bacteria is connected to lesser negative emotionality and fear reactivity. The study also considered other factors that significantly affect the diversity of the microbiota, such as the delivery method and breastfeeding.

This shows a baby and a little girl
The newly published study is first of its kind and gives evidence of an association between normal variation in behaviour and gut microbiota. The image is in the public domain.

The findings are interesting as a strong fear reaction and negative emotionality can be connected to depression risk later in life. However, the association with later diseases is not straightforward and they are also dependent on the environment.

“Although we discovered connections between diversity and temperament traits, it is not certain whether early microbial diversity affects disease risk later in life. It is also unclear what are the exact mechanisms behind the association,” adds Aatsinki.

“This is why we need follow-up studies as well as a closer examination of metabolites produced by the microbes.”

The newly published study is first of its kind and gives evidence of an association between normal variation in behaviour and gut microbiota. This might indicate that there is activity on the gut-brain axis already in infancy. The gut-brain axis is a functional relationship between gut flora and central nervous system via the nervous, immune and endocrine systems.

The FinnBrain research project of the University of Turku studies the combined influence of environmental and genetic factors on the development of children. Over 4,000 families participate in the research project and they are followed from infancy long into adulthood. The newly published study is part of FinnBrain’s gut-brain axis sub-project led by Adjunct Professor, Child and Adolescent Psychiatrist Linnea Karlsson.

About this neuroscience research article

University of Turku
Media Contacts:
Anna Aatsinki – Neuroscience News
Image Source:
The image is in the public domain.

Original Research: Open access
“Gut microbiota composition is associated with temperament traits in infants”. Anna Aatsinki et al.
Brain, Behavior, and Immunity. doi:10.1016/j.bbi.2019.05.035


Gut microbiota composition is associated with temperament traits in infants


One of the key behavioral phenotypes in infancy are different temperament traits, and certain early life temperament traits have been shown to precede later mental health problems. Differences in the gut microbiota composition (GMC) have been suggested to link with neurodevelopment. For example, toddler temperament traits have been found to associate with differences in GMC; however, studies in infants are lacking although infancy is a rapid period of neurodevelopment as well as GM development. Thus, we aimed to investigate association between infant GMC and temperament.

The study population (n = 301, 53% boys) was drawn from the FinnBrain Birth Cohort Study. Stool samples were collected from the 2.5-month-old infants and sequenced with 16S Illumina MiSeq platform. GMC taxonomic composition (at Genus and OTU level), observed sample clusters, diversity and richness were investigated in relation to the maternal reports of Infant Behavior Questionnaire -Revised (IBQ-R) at the age of 6 months.


Three sample clusters (Bifidobacterium/Enterobacteriaceae, Bacteroides, V. Dispar) based on GMC were identified, of which Bifidobacterium/Enterobacteriaceae–cluster presented with higher scores on the IBQ-R main dimension regulation and its subscale duration of orienting compared to Bacteroides-cluster. The clusters associated with temperament in a sex-dependent manner. The IBQ-R main dimension surgency (positive emotionality) was associated positively both with genus Bifidobacterium and Streptococcus. Alpha diversity had a negative association with negative emotionality and fear reactivity.


This is the first study demonstrating associations, but not causal connections, between GMC and temperament in young infants in a prospective design.

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