Original Article

Molecular Psychiatry (2016) 21, 717–721; doi:10.1038/mp.2015.116; published online 25 August 2015

Common psychiatric disorders share the same genetic origin: a multivariate sibling study of the Swedish population

E Pettersson1, H Larsson1 and P Lichtenstein1

1Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden

Correspondence: Dr E Pettersson, Medical Epidemiology and Biostatistics, Karolinska Institutet, Box 281, Stockholm 17177, Sweden. E-mail: erik.pettersson@ki.se

Received 24 August 2014; Revised 8 June 2015; Accepted 15 June 2015
Advance online publication 25 August 2015



Recent studies have shown that different mental-health problems appear to be partly influenced by the same set of genes, which can be summarized by a general genetic factor. To date, such studies have relied on surveys of community-based samples, which could introduce potential biases. The goal of this study was to examine whether a general genetic factor would still emerge when based on a different ascertainment method with different biases from previous studies. We targeted all adults in Sweden (n=3475112) using national registers and identified those who had received one or more psychiatric diagnoses after seeking or being forced into mental health care. In order to examine the genetic versus environmental etiology of the general factor, we examined whether participants’ full- or half-siblings had also received diagnoses. We focused on eight major psychiatric disorders based on the International Classification of Diseases, including schizophrenia, schizoaffective disorder, bipolar disorder, depression, anxiety, attention-deficit/hyperactivity disorder, alcohol use disorder and drug abuse. In addition, we included convictions of violent crimes. Multivariate analyses demonstrated that a general genetic factor influenced all disorders and convictions of violent crimes, accounting for between 10% (attention-deficit/hyperactivity disorder) and 36% (drug abuse) of the variance of the conditions. Thus, a general genetic factor of psychopathology emerges when based on both surveys as well as national registers, indicating that a set of pleiotropic genes influence a variety of psychiatric disorders.