My research group has strong skills in advanced epidemiological analyses and uses the unique possibilities in Sweden to perform psychiatric epidemiological research based on national health registers, twin research using the Swedish twin register and molecular epidemiology using large scale data collections of DNA. The group has also developed strong links to clinic research, where we perform translation research based on quality registers, randomized control trials, and clinically based data collections.
2003-2005: Doctoral student, Dept. of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm
2006: Post-doctoral fellow, Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London.
2007-2009: Postdoctoral position at the Dept. of Medical Epidemiology and Biostatistics, Karolinska Institutet.
2010: Assistant professor at the Karolinska Institutet Center of Neurodevelopmental Disorders and Dept. of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm
2011-: Associate Professor at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm
2013-2015: Director of Doctoral Education in Epidemiology at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet
2016- Guest Professor at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet
2016- Professor at the School of Medical Sciences, Örebro University
Our research group has strong skills in advanced epidemiological analyses and uses the unique possibilities in Sweden to perform psychiatric epidemiological research based on national health registers, twin research using the Swedish twin register and molecular epidemiology using large scale data collections of DNA. Our group has also developed strong links to clinic research, where we perform translation research based on quality registers, randomized control trials, and clinically based data collections.
Short presentation of current research on ADHD
What are the benefits and risks associated with ADHD medication use?
We have shown that ADHD medication reduce the risk for serious and public-health relevant outcomes, including criminality and traffic accidents. Our studies found no evidence for harmful effects of ADHD medication on substance abuse; rather the association between ADHD and substance abuse was explained by shared familial risk factors. Our studies also suggest that the co-occurrence of ADHD and suicidal behavior is due to shared familial factors, rather than to harmful effects of ADHD medications.
Is ADHD characterized by both continuity and change across the life span?
This far, we have been able to demonstrate that symptoms of inattention tend to persist from childhood into adolescence to a greater extent than symptoms of hyperactivity-impulsivity. We have also shown that the level of the inattention symptoms may increase in some individuals from childhood to adolescence, which may lend developmental insight into how the presentation of ADHD symptoms changes from childhood to adulthood. We have used twin data to demonstrate that both stable and dynamic genetic risk factors influence ADHD over the course of the development from childhood into adulthood. We have recently shown that physical activity in adolescence might decrease ADHD symptoms in early adulthood.
Is ADHD best viewed as a categorical disorder or as an extreme of a continuous trait?
We have used twin data to demonstrate a strong genetic link between the extreme and the sub-threshold variation of ADHD symptoms. We have also shown that the association between reduced birth weight and ADHD symptoms extend beyond the extreme end of the ADHD distribution, including the sub-diagnostic threshold range. Together, this suggest that ADHD is best viewed as the quantitative extreme of genetic and environmental factors operating dimensionally throughout the distribution of ADHD symptoms, indicating that the same etiologic factors are involved in the full range of symptoms of inattention, hyperactivity and impulsivity.
How do genetic and environmental risk factors contribute to ADHD across the life span?
Our research group use twin data to study how genetic and environmental risk factors contribute to ADHD across the life span. Among many things, we have been able to demonstrate that ADHD in adults is strongly influenced by genetic risk factors and that the previous reports of low heritability for ADHD in adults are best explained by rater bias. We have recently published a review of the available twin research on ADHD in adults.
Why individuals with ADHD also presents with other psychiatric disorders?
We use twin and family data to obtain a better understanding of why individuals with ADHD also presents with other psychiatric disorders. We have clarified the role of genetic and environmental factors for several comorbid disorders and traits, including asthma, externalizing behavior, substance use problems, autistic traits, temperamental traits, and emotional lability. We have also conducted a large family study to show that ADHD share genetic risk factors with bipolar disorder and schizophrenia.
Is ADHD influenced by early risk factors?
Our research team uses genetically informative designs to better understand associations between early risk factors and ADHD. We have shown that even though maternal smoking during pregnancy and maternal obesity in early pregnancy are associated with ADHD in offspring, they are not causally related; rather these associations were explained by unmeasured familial confounding. Using the same methods we have shown that cousins within the extended family and siblings within the same nuclear family who were differentially exposed to family income during early childhood actually differed in ADHD risk, which support a causal interpretation. Sibling and cousin analyses have also revealed that preterm birth and advancing paternal age is strongly associated with offspring risk for ADHD even after controlling for genetic confounding, again consistent with a causal interpretation. We have also explored how ADHD associates with maternal stress during pregnancy and maternal age at childbirth.
Main supervisor for PhD students
Co-supervisor for PhD students
- Johan Zetterqvist, MEB, KI.
- Gustaf Brander. Dep. of Clinical Neuroscience
- Heléne Sundelin, Örebro university
- Cecilia Lundholm, MEB, KI
Past doctoral students
- Mats Forsman, PhD. (Thesis defense: 2009-09-25). Dep. of Medical Epidemiology and Biostatistics (MEB), Karolinska Institutet (KI);
- Zheng Chang PhD (Thesis defense: 2013-11-08) MEB, KI;
- Therese Ljung, PhD (Thesis defense: 2014-01-30). MEB, KI
- Charlotte Skoglund, PhD (Thesis defence: 2015-11-06). Centrum för psykiatriforskning, KI.
- Qi Chen, PhD (Thesis defence: 2016-03-18). MEB, KI.
- Andrea Johansson, Capusan,PhD (Thesis Defence: 2016-09-02). Linköping University
Current post docs
- M.A. Psychology (2001), Örebro University, Sweden
- PhD in Genetic Epidemiology (2005), Karolinska Institutet
Academic honours, awards and prizes
I received the Fuller and Scott Early Career award by the Behavior Genetic Association in 2013.
My past PhD students Zheng Chang and Qi Chen have both received the “Chinese government award for outstanding self-financed students abroad”.