Introducing Hasse Karlsson, Professor of Integrative Neuroscience and Psychiatry

A Holistic Approach to Understanding Brain Development  

Professor Hasse Karlsson is a pioneering researcher in brain development with an extensive career as a psychiatrist. He was appointed as a Professor of Integrative Neuroscience and Psychiatry at the University of Turku, where he founded the FinnBrain Birth Cohort together with Associate Professor Linnea Karlsson, one of the largest and most versatile birth cohorts in the world. He is currently the new Chair of Neurocenter Finland’s National Steering Board, a new step to strengthen neuroscience in Finland.

Early Career  

Becoming a doctor has been Hasse’s dream since he was a teenager, and his determination to pursue this path was unwavering. After joining medical school, he developed an interest in psychiatry and studying the brain, even though there was a direction toward the psychodynamic approach at that time. However, his interest in the brain persisted and, eventually, became a cornerstone of his career as a doctor and researcher. Hasse’s curiosity about the brain encouraged him to pursue a master’s degree in theoretical philosophy simultaneously with his medical degree, where he studied the brain-mind problem. He completed both degrees in the 1980s before starting his clinical work. 

Hasse started working on his PhD shortly after beginning his residency, focusing on studying patients with vague symptoms who frequently visited the clinics. He aimed to categorize them according to their symptoms to understand their overall situation, including psychiatric problems. The project ended in 1996 when Hasse obtained his PhD and decided to continue his brain research. 

“After the PhD, I joined Turku PET Center in their early clinical studies. Using PET imaging, I studied serotonin receptors in the brain and their role in depression. In addition, I was also involved in emotion-processing studies. While these studies were smaller in scale with minimal study groups, they were my first attempts to pursue my research studying the brain.”  

Hasse was then appointed as the Professor of Psychiatry at the University of Helsinki, where he was involved in several cross-sectional studies investigating certain illnesses and their brain correlation. “I became more skeptical about this approach and wanted to study the underlying mechanisms behind developing these illnesses and the brain over the years.”   

Driven by his interest in studying brain development, Hasse returned to Turku, where he drew the groundwork for the FinnBrain Birth Cohort in 2010 with the support of a grant from the Academy of Finland. Later in 2012, he became the Professor of Integrative Neuroscience and Psychiatry at the University of Turku, a new title emphasizing the vital role of integration in progressing neuroscience research. In addition, Hasse resumed his clinical work, in which he held the role of a chief physician at the Turku University Hospital. 

The FinnBrain Birth Cohort: A Comprehensive Look at Early Life Stress Exposure

Previously examined by epidemiological studies, stress was considered a triggering factor for the onset of many psychiatric and somatic disorders. However, it was not extensively studied, especially the impact of early stress exposure on brain development. To address this gap, Hasse started the FinnBrain Birth Cohort to study the role of environmental and genetic factors, specifically by collecting data starting from pregnancy as the earliest possible brain development phase. “Initially, our focus was only on maternal stress, but we have found interesting data showing that paternal early life stress is also associated with child brain development. We now realize that starting one generation earlier would have helped us get a more inclusive picture.” (e.g., JAMA Netw Open. 2020;3(11):e2024832. DOI:10.1001/jamanetworkopen.2020.2483)

After almost ten years of starting data collection, the children are now approaching their teenage years, marking a new phase in the research outcomes. 

“This next stage of the study is critical as the incidence of illnesses such as psychiatric disorders increases during puberty. Nevertheless, one unique aspect of the cohort is its longitudinal and integrative approach, as the impact of early life stress may not be seen until later in life, such as in dementia, cognitive decline, and cardiovascular diseases. Therefore, the cohort will continue to collect data on the children’s development to track long-term outcomes throughout their life span.”  

While the study aimed to recruit 10,000 families, the target was adjusted to 4,000, which took around three years of recruitment from Finland. Despite focusing on children’s brain development, samples from the parents were also collected. The data includes blood and cord blood samples, ultrasound measurements, neuroimaging data, genetic data, parental stress levels, psychiatric symptoms, and sperm samples from the parents, just to mention a few. 

“Most DNA has already been extracted, and there have been several publications on the topic. Furthermore, researchers are now exploring new areas of genetics, such as epigenetics, by measuring DNA methylation and the telomere lengths linked to aging and disease, analyzed from blood samples and the placenta. Additionally, the non-coding RNAs are measured from sperm samples.” (e.g., Neurobiol. of Stress. 2021 November;15. DOI:10.1016/j.ynstr.2021.100374)

On the other hand, FinnBrain research has expanded to include several topics, such as sleeping disturbances with Associate Professors Linnea Karlsson and Juulia Paavonen, gut microbiota with Dr. Anna Aatsinki, neuropsychological investigations with Professor Riikka Korja and her team, and speech and language pathology with Professor Elina Mainela-Arnold. One unexpected addition was the dental study initiated by Professor Satu Lahti, who was interested in studying dental fear and anxiety. Their latest publication found that smoking parents had higher dental anxiety levels than non-smokers. (Eur J Oral Sci. 2023;e12912. DOI:10.1111/eos.12912)

“This diversity in the topics, with over 150 published papers and nearly 20 PhD, revealed many interesting findings. For example, by linking the neuropsychological measurements with the brain imaging results, we could study the connection between parental stress levels to the development of the child’s brain structures.”  

Currently, the group comprises around 20 to 30 core researchers, but the whole group is around 200 with over 45 PhD candidates working on the project. Additionally, the FinnBrain has started its international congress to gather interested researchers in the field. This year’s theme will cover prenatal and early life stress and its implications for brain development.  

Regional and Global Collaborations in Brain Development  

National and international collaboration comes into the heart of Hasse’s and FinnBrain’s work. Since the beginning, the FinnBrain has cooperated with other cohorts inside Finland, such as the cardiovascular cohort with Professor Olli Raitakari and the child-sleep cohort with Professor Tiina Paunio, among others. “The Population Research Center helped boost the collaboration between research groups in Finland by collecting the major cohorts data in the region.”  

Internationally, the FinnBrain has been actively involved in several projects. Hasse and his group have worked with leading researchers from several institutions in Europe and America. 

“We are collaborating internationally with different research groups on different levels. For example, we work with John Lewis at Montreal Neurological Institute in neuroimaging data analysis. We also collaborated with researchers from Cork, Ireland, to study gut microbiota. From Berlin, we are working with Claudia Buss and Sonja Entringer to study early stress exposure and Ana Rodriguez’s and Nuno Sousa’s animal model studies. Furthermore, we have been working with Michelle Fernandes in the UK on her neurocognitive development research with her big cohorts. We also have some collaborations in the US, Belgium, and Spain.”  

“The Generation R Birth Cohort group in Rotterdam, the Netherlands has been a source of inspiration for starting FinnBrain. During the first stages of the project, the group played a crucial role and made a significant contribution, providing details about all the practicalities and obstacles we could face.” 

Furthermore, the FinnBrain Birth Cohort has recently joined three significant projects. The first is a Center of Excellence-funded study with the University of Jyväskylä to study learning disabilities. The second project, granted by Strategic Research – STN, will investigate the sense of loneliness in children. Lastly, the INITIALISE project, coordinated by Professor Matej Orešič at the University of Turku, delves into the impact of environmental factors on immune system development. With their expertise in neurocognitive data analysis, Hasse’s team will study the association between early immune system development and neurocognitive outcomes and brain maturation. 

Turku’s Neuroscience Research: A Journey of Collaboration and Progress  

In addition to his extensive research and clinical work, Hasse was involved in the early formation of the Turku Brain and Mind Center (TBMC) 20 years ago. Originally established as the Turku Neuroscience Center, the idea was to create an entity to gather neuroscience researchers in the Turku area. The project then lost momentum after the appointment of Hasse and two of its central figures, including Professors Esa Korpi and Antti Pertovaara, as professors at the University of Helsinki. However, after Hasse’s return to Turku, the project was revived with other interested researchers’ support. As a result, TBMC was officially established in 2011 as an umbrella for interested researchers to work together. 

“At its early stages, TBMC was based on its members’ efforts without financial support from the university, which was a challenging obstacle at the beginning. Gradually, we secured some funding from various faculties at the University of Turku and Åbo Akademi University. With the universities’ support, we could start the first master’s degree in neuroscience in Turku in 2018.”  

TBMC has made remarkable progress over the years. The educational part has been the essential aspect thus far with the Master’s Degree Program in Human Neuroscience, attracting students from inside and outside Finland. TBMC is now part of the Network of European Neuroscience Schools (NENS), which could facilitate collaboration with other institutions. Looking to the future, the TBMC could benefit from increased collaboration with industry and among research groups in Turku. 

“Turku has a solid standing in neuroscience research, with many exceptional research groups operating in the area. TBMC could facilitate communication between these groups to create harmony for better research outcomes. We could also have a future doctoral program in neuroscience to have a whole educational curriculum and good researchers.”  

Hasse has been acting as TBMC’s Chair since its inception, and now the current Chair is Associate Professor Juho Joutsa

Advancing the Finnish Neuroscience Community  

As of January 2023, Hasse has taken on a new role as the Chair of the National Steering Board at Neurocenter Finland. One of his main goals is to form a stronger neuroscience community in Finland by creating a collaborative environment that fosters communication and collaboration among different research groups. To achieve this goal, Hasse is working with Neurocenter Finland’s board to establish clear visions for the future and take their first practical steps in achieving them. 

“Although we have strong neuroscience research in Finland, the groups have been scattered around the country, and there has not been that much collaboration. Neurocenter Finland has been aiming to be a platform through which researchers can communicate, collaborate on research projects, and find synergies among each other since its early beginning. Our main vision for the upcoming years is to build a big cohesive community of neuroscience researchers and create more collaborations on the national and international levels as well as build contacts with commercial companies.”  

“Neurocenter Finland has already started to promote research activities and collaborations in Finland by organizing events such as the regular BrainBreak online meetings. However, there is a need now for more in-person social gatherings in addition to current online meetings to encourage researchers of diverse backgrounds to participate and share their knowledge.”  

The importance of building a neuroscience research community cannot be overstated. Researchers can share their knowledge and expertise, collaborate on projects, and address common challenges by coming together. Moreover, as the neuroscience sector grows, researchers must work together to advance the field and make discoveries that will benefit society. 

“Now that we have the structure, plan, and finances, the work is in progress. Hopefully, in a couple of years, we can have a bigger Finnish neuroscience community and see the impact we aimed for.”