Published: 23-05-2013 00:00 | Updated: 30-10-2014 09:39

Common genes responsible for ADHD, schizophrenia and bipolar disorder

A new study from Karolinska Institutet shows that ADHD might, in part, have the same genetic causes as schizophrenia and bipolar disorder. Participating in the study, which is published in the scientific periodical The British Journal of Psychiatry, were over 60,000 individuals with ADHD and their relatives.

Scientists have recently become increasingly interested in the association between neuropsychiatric disability in childhood and severe adult psychiatric conditions, but their understanding of these connections has been limited. To examine whether ADHD, schizophrenia and bipolar disease have common causes Swedish researchers have now analysed data from a number of Swedish national registers, such as the patient registry and the multi-generation register.

The study included 61,187 individuals diagnosed with ADHD and their relatives. The results reveal that people with ADHD run a greater risk of developing schizophrenia and bipolar disease. They were also found to be more likely to have close relatives (parents, children, full siblings) with these conditions. The risk bipolar disorder and schizophrenia was half as high in their second-degree relatives (half-siblings) compared to first-degree relatives.

"Taken together, the results support the notion that ADHD, schizophrenia and bipolar disorder partly share a common genetic background," says Dr Henrik Larsson, associate professor at Karolinska Institutet's Department of Medicinal Epidemiology and Biostatistics. "The study sheds light on the links between psychiatric conditions that were previously assumed to be completely distinct."

The study was financed with grants from the Swedish Research Council, the National Institute of Child Health and Human Development (NICHD) and the Stockholm County Council through its ALF agreement (on medical education and research) with Karolinska Institutet.