Ola Olén

Ola Olén

Adjunct Senior Lecturer | Docent
Visiting address: Maria Aspmans gata 30A, 17164 Solna
Postal address: K2 Medicin, Solna, K2 KEP Olén O, 171 77 Stockholm

About me

  • Olén is an associate professor (docent in Swedish), group leader, and adjunct senior lecturer (lektor in Swedish) at the Division of Clinical Epidemiology at the Department of Medicine Solna, Karolinska Institutet. He is also a senior consultant (överläkare in Swedish) at the Department of pediatric gastroenterology and nutrition at Sachs’ children and youth hospital, Stockholm.



    The aim of my research is to improve health care and ultimately quality of 

  • life for patients suffering from diseases such as inflammatory bowel disease
    (IBD) or functional gastrointestinal disorders such as irritable bowel
    syndrome (IBS).

    As a pediatric gastroenterologist, most of my clinical time is devoted to
    patients with IBD. They are sometimes severely ill and require advanced
    treatment. In my research group, we use large register-based linkages including all IBD
    patients in Sweden and matched controls. Our IBD research is conducted in 

  • national and international collaboration and is based on clinical data in
    national health registers and local registers or biobanks.

    Important research questions that we explore are for instance: Why do some people get IBD? What is the
    prognosis for different patient groups with IBD (and especially for patients with childhood onset)? Different treatments for IBD
  • Are they effective? Are they safe? And are they cost effective?

    Dr Olén is a member of the steering committee for the national quality register for IBD care (www.swibreg.se), the steering group for the Swedish national guidelines in pediatric IBD, and of the Pediatric IBD Porto group of ESPGHAN (European Society for Paediatric Gastroenterology, Hepatology, and Nutrition). He is also a member of the steering groups for the Swedish national guidelines for pediatric functional abdominal pain disorders and pediatric celiac disease.

    Irritable bowel syndrome (IBS) and other types of functional abdominal pain disorders are very common: Approximately 3% of all visits to the general practitioner, 10% of visits to general pediatricians and 20% of visits to a pediatric gastroenterology unit.

    It is well known that cognitive behavior therapy and hypnotherapy are effective for children and adolescents with IBS, but access to trained therapists is very limited. In randomized clinical trials we test if it is possible to treat children and adolescents with IBS or functional abdominal pain via internet, thereby increasing accessibility to evidence-based treatments for these large patient groups.

    I am also trying to understand why so many children suffer from IBS by studying risk factors for disease in birth cohorts and national health registers. In these data sources we are studying the effects of genetics, perinatal risk factors, lifestyle, co-morbidity, gut flora, and use of antibiotics.


    *Olén O*, Erichsen R, Sachs MC, Pedersen L, Halfvarson J, Askling J, Ekbom
    A, Toft-Sørensen H, Ludvugsson JF. Colorectal cancer in ulcerative colitis:
    a Scandinavian population-based cohort study. *Lancet*. 2020

    *Olén O*, Askling J, Sachs MC, Frumento P, Neovius M, Smedby KE, Ekbom A,
    Malmborg P, Ludvigsson JF.
    Childhood onset inflammatory bowel disease and risk of cancer: a Swedish
    nationwide cohort study 1964-2014. *BMJ* 2017

    *Olén O*, Askling J, Sachs MC, Frumento P, Neovius M, Smedby KE, Ekbom A,
    Malmborg P, Ludvigsson JF.
    Increased Mortality of Patients with Childhood-onset Inflammatory Bowel
    Diseases, Compared With the General Population. *Gastroenterology* 2018

    Everhov ÅH, Halfvarson J, Myrelid P, Sachs MC, Nordenvall C, Söderling J,
    Ekbom A, Neovius M, Ludvigsson JF, Askling J, *Olén O*.
    Incidence and Treatment of Patients Diagnosed With Inflammatory Bowel
    Diseases at 60 Years or Older in Sweden. *Gastroenterology* 2018

    Bonnert M, *Olén O*, Lalouni M, Benninga MA, Bottai M, Engelbrektsson J,
    Hedman E, Lenhard F, Melin B, Simrén M, Vigerland S, Serlachius E, Ljótsson
    B. Internet-Delivered Cognitive Behavior Therapy for Adolescents With
    Irritable Bowel Syndrome: A Randomized Controlled Trial. *Am J
    Gastroenterol*. 2017

    Lalouni M, Ljótsson B, Bonnert M, Ssegonja R, Benninga M, Bjureberg J,
    Högström J, Sahlin H, Simrén M, Feldman I, Hedman-Lagerlöf E, Serlachius
    E, *Olén O*. Clinical and Cost Effectiveness of Online Cognitive
    Behavioral Therapy in Children with Functional Abdominal Pain
    Disorders. *Clin Gastroenterol Hepatol*. 2018


  • Dr Olén is a valued teacher, regularly and often engaged as a lecturer regarding inflammatory bowel disease, irritable bowel syndrome, and epidemiology. Apart from his regular lectures, seminars, and bedside education of medical students at Karolinska Institutet, dr Olén has served as the director of studies 2009-2013 for the widely acclaimed Research school in epidemiology for clinicians at the Karolinska Instituet (Department of Medicine Solna) and 2014-2015 he was the director of studies for the Clinical research school (Department of Clinical Science and Education). He has been director of a national course in pediatric gastroenterology, hepatology, and nutrition, funded by the National Board of Health and Welfare 2012-2017. 

  • Former PhD students: Bonnert M, Uusijärvi A, Lalouni M, Granlund J,
    Schollin-Ask L, Forss A, Mouratidou N, Mahmood M, Thulin H
    Current PhD students: Sjölund J, Jossan N, Andersson F

    Former Postodocs: Arnell H, Malmborg P, Everhov ÅH
    Current Postdocs: Bröms G, Eriksson C, Rolandsdotter H, Forss A, Soini T


All other publications



  • Senior consultant in paediatrics, Sachs' Children and Youth Hospital, 2016-
  • Adjunct Senior Lecturer, Department of Medicine, Karolinska Institutet, 2023-2025

Degrees and Education

  • Docent, Karolinska Institutet, 2020
  • Degree Of Doctor Of Philosophy, Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, 2008

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