Linnea Karlsson has had a successful career as a specialist and researcher in child and adolescent psychiatry. She is currently an associate professor at the Centre for Population Health Research, established in Turku in 2019. The University of Turku and the Hospital District of Southwest Finland coordinate several nationally and internationally significant cohort studies. Linnea Karlsson, together with her husband professor Hasse Karlsson, has conceived and launched one of the most significant birth cohorts in Southwest Finland, the FinnBrain study. The main aim of the study has been to investigate associations between early life stress and the development of a child’s brain and health. The cohort population consists of children born in the Turku area and Åland Islands in 2012-2015 and their parents.

My specialty is becoming clearer

Karlsson defended her dissertation at the University of Helsinki in the early 2000s on the epidemiology of depression in adolescents in Finland. After her dissertation, she completed the qualifications of a specialist in both child and adolescent psychiatry at the University of Turku.

However, a career as a doctor or researcher was not a dream of Linnea’s youth, instead, she was interested in her native language and literature, and thought she could become a language teacher or journalist. On the other hand, she was also very interested in the natural sciences, and in her last year of high school, studying medicine began to seem like the best option.

• The Faculty of Medicine began to sound like it would give a profession that allows you to do many things. In the Faculty of Medicine, around year 3-4 of my studies, I considered leaving, and I was still planning to study in the Faculty of Humanities, but then in the latter part of my studies with psychiatry courses I began to realize new opportunities to combine science to a humanistic attitude to life.

Linnea, a Bachelor of Medicine at the time, actually drifted into the field of adolescent psychiatry by chance because she worked for a summer at Peijas Hospital under the supervision of Mauri Marttunen, a professor of adolescent psychiatry. Mauri also came up with the idea to research depression in adolescents, and the research career in psychiatry gradually began to take shape.

The material in the dissertation was the pilot material of the current Health 2000 study, pioneering in the sense that adolescents themselves were asked about their symptoms of depression. Diagnostic interviews for adults had just been introduced in psychiatric epidemiology in the late 1990s: the persons themselves are interviewed about their symptoms, and this provides population-level information about the phenomenon. But the idea of asking adolescents themselves about their depressive symptoms was entirely new.

• After the dissertation I had already gone so far, and I realized that research work is really nice, and life without research started to be unthinkable to me.

Today, Linnea thinks that having also done clinical work with people is important for her research work. Methodological expertise alone may not provide the research topics that are important for the whole or for developing patient care.

My own cohort material is starting to take shape

After Linnea’s dissertation, ideas for her new, longitudinal study began to find direction. Together with Hasse Karlsson, they began to consider doing science with a glint in their eyes. Both Hasse and Linnea came from the field of depression research, and the first acronym describing their research was ”SAD brain – Stress, Attachment, Depression”. At that time, in the mid-2000s, there were hints that prenatal stress exposure might be an important factor in a child’s development and that the adverse effects of stress were of general interest.

• We were interested in the effects of stress exposure, interactions and depression. We specifically wanted to study the effects of prenatal stress and decided that the most sensible way to study this is to set up a birth cohort.

In 2010, FinnBrain received its first funding from the Academy of Finland. Since then, the research has expanded into a large, multidisciplinary research project with many work packages or smaller teams working under the “FinnBrain umbrella”. However, magnetic resonance imaging of infant brain has been one of the original research focuses. One of Linnea’s first grants was to start magnetic resonance imaging of infants’ brains. Now, this branch of research has also expanded, and the Neuroimaging lab is now led by Doctor of Medicine, Adjunct Professor Jetro Tuulari.

• Researchers have introduced their own ideas, and through these colleagues, who have joined, our project has expanded, and new research topics have been introduced, although the focus still is in stress exposure and its health effects.

Building a close-knit community has been a driving force in leading such a large but closely connected research community.

• From the beginning, Hasse and I had the idea that it should be nice to come to work. It has been important for us that the atmosphere at work remains good, and people’s well-being is important. Even during the corona pandemic, we have tried to maintain good team spirit by celebrating the publication of an article in the park, drinking champagne while wearing mittens.

Latest research results and future focuses

Linnea Karlsson leads FinnBrain’s “Gut-Brain Axis” lab. This team has discovered important new information about the development of the gut-brain axis in humans. MD Anna Aatsinki was the first researcher to defend her dissertation on this theme. According to the findings of the dissertation, the composition of the gut microbiota of early childhood is associated with later temperament and emotional attention. In addition, the dissertation showed that maternal stress during pregnancy appears to be associated with the child’s gut microbiota composition.

• MD Anna Aatsinki summed up her dissertation last year as follows: In the future, this new area of research may potentially contribute to the development of new therapies, although the long-term effects of the different composition of early gut microbiota and the underlying mechanisms remain partially unclarified.

In the case of gut microbiota, research methods have developed over the years, and it is now possible to determine more precisely both the composition of the microbiota and the metabolism. In the future, the idea is to find out more about the connection of gut microbiota metabolites to neuropsychological development and child psychiatric phenomena.

Importance of networks and communities

Linnea considers research collaboration important, and FinnBrain research is widely networked both nationally and internationally. Collaborative relationships have been formed internationally, either through substance know-how or, on the other hand, through having fun, when meeting people with whom cooperation is effortless while common research areas get developed.

Examples of domestic co-operation are a consortium in sleep research with the University of Tampere, the Finnish Institute for Health and Welfare and the University of Helsinki, or the paediatric sub-study being part of the FINMIC (Finnish Platform of Birth Cohorts) consortium, which, in addition to Turku, includes the University of Helsinki, the University of Eastern Finland, the Finnish Institute for Health and Welfare and the University of Oulu. There has been co-operation with the University of Tampere in eye movement research and the newly established InterLearn Centre of Excellence with the University of Jyväskylä, just to name few.

Finally, Linnea wants to emphasize the importance of community also for the development of children. In order to develop, children’s brains need unhurried human contact.

• Overall, the significance of other people is understood too little in our society. Support by other people and communities are super-important in nurturing the brain of a child. The human brain seems to need “live” interaction to grow, whereas digital interaction is not necessary for the brain, and it can be harmful to the developing brain if there is too little of the necessary stimulus when a less necessary stimulus takes up too much time.

The purpose of the FinnBrain study is to follow the children of the cohort until adulthood and possibly beyond. They are now starting the children’s 9-year visits. Early life stress exposure is still the focus of the research. Until now, the questionnaires have been aimed at parents, but in the future, researchers will want to ask children more about their own experiences, e.g. of negative life events. See the University of Turku’s bulletin on the subject: https://www.utu.fi/fi/ajankohtaista/mediatiedote/tutkimuksessa-selvitetaan-lasten-kokemuksia-kielteisista

Read more about Finnbrain study:
https://sites.utu.fi/finnbrain/en/