Ola Olén, Senior researcher

Ola Olén

Adjunct senior lecturer

About me

Ola Olén is a senior consultant at the Department of pediatric gastroenterology and nutrition at Sachs’ children and youth hospital and an associate professor at the Clinical Epidemiology Division at the Department of Medicine Solna, Karolinska Insitutet.

Research description

My research

The aim of my research is to improve healthcare 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. I am PI for a large register-based linkage including all IBD patients in Sweden and matched controls. My IBD research is conducted in national and international collaboration and is based on clinical data in national health registers and local 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 safe? And are they cost effective?

I am  a member of the steering committee for the national quality register for IBD care (www.swibreg.se), the steering group for the Swedish guidelines in pediatric IBD, and of the Pediatric IBD Porto group of ESPGHAN (European Society for Paediatric Gastroenterology, Hepatology, and Nutrition).


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 25% of visits to a pediatric gastroenterology unit.

It is well known that cognitive behavior therapy is 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 (read more on www.ontimagen.nu). 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.


Selected references:

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

Khalili H, Granath F, Smedby KE, Ekbom A, Neovius M, Chan AT, Olen O.
Association Between Long-term Oral Contraceptive Use and Risk of Crohn's Disease Complications in a Nationwide Study. Gastroenterology. 2016

Olén O, Askling J, Sachs MC, Neovius M, Smedby KE, Ekbom A, Ludvigsson JF. Mortality in adult-onset and elderly-onset IBD: a nationwide register-based cohort study 1964-2014. Gut. 2019

Ludvigsson JF, Mahl M, Sachs MC, Björk J, Michaelsson K, Ekbom A, Askling J, Backman AS, Olén O. Fracture Risk in Patients With Inflammatory Bowel Disease: A Nationwide Population-Based Cohort Study From 1964 to 2014. Am J Gastroenterol. 2019

Khalili H, Neovius M, Ekbom A, Ludvigsson JF, Askling J, Chan AT, Olen O.
Oral Contraceptive Use and Risk of Ulcerative Colitis Progression: A Nationwide Study. Am J Gastroenterol. 2016

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

Teaching portfolio

Dr Olén served as the director of studies 2009-2013 for the widely acclaimed Research school in epidemiology for clinicians at the Karolinska Instituet. He has been director of a national course in pediatric gastroenterology, hepatology, and nutrition, funded by the National Board of Health and Welfare 2013-2017. Dr Olén is a valued teacher and often engaged as a lecturer regarding inflammatory bowel disease, irritable bowel syndrome, and epidemiology.

Former PhD students: Bonnert M, Uusijärvi A, Lalouni M, Granlund J, Schollin-Ask L

Current PhD students: Mouratidou N, Thulin H, Forss A, Sjölund J, Jossan N, Mahmood M

Former Postodocs: Arnell H, Malmborg P, Everhov ÅH

Current Postdocs: Bröms G, Eriksson C, Rolandsdotter H



Specialist in pediatrics, 2011

PhD, 2008, Karolinska Institutet

Medical degree, 2000, Uppsala University.


Clinical positions:

2017 – : Senior Consultant, Sachs’ Children’s hospital. Researcher, Karolinska Institutet.

2014 – 2016: Consultant, Sachs’ Children’s hospital. Postdoc, Karolinska Institutet.

2011 – 2013: Specialist in pediatrics, Sachs’ Children’s hospital (0% research)

2002 – 2010: Specialist training, Sachs’ (incl. parental leave and PhD-studies.)

2000 – 2002: Internship, Sunderby Sjukhus

Academic honours, awards and prizes

- Young scholar award 2018, Strategic Research Area Epidemiology (SfoEpi) at Karolinska Institutet

- Clinical researcher award 2017 ("klinisk forskartjänst"), Karolinska Institutet/Stockholm County

- Mag- Tarmfondens stora pris 2016 (”the great prize of the Swedish gastro society”).

- Bengt Ihre research fellowship in gastroenterology 2014-2016 (www.ihrefellowship.se). Awarded by the Swedish medical association to promising future research leaders in gastroenterology. Includes a 2 year grant and networking activities with prominent researchers in gastroenterology during the grant period and afterwards.

- ìShizu Matsumuraîs donation 2013, to prominent pediatric research at KI.


Our research is also conducted with support from: The Swedish Research Council, The Swedish Research Council for Health, Working Life, and Welfare, The Swedish Medical Society, and the Regional Agreement on Medical Training and Clinical Research between Stockholm County Council and Karolinska Institutet (ALF).