a1 Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
a2 Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, WA, USA
a3 Department of Psychiatry, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA
Background Psychiatric conditions in which symptoms arise involuntarily (‘diseases’) might be assumed to be more heritable than those in which choices are essential (behavioral disorders). We sought to determine whether psychiatric ‘diseases’ (Alzheimer's disease, schizophrenia, and mood and anxiety disorders) are more heritable than behavioral disorders (substance use disorders and anorexia nervosa).
Method We reviewed the literature for recent quantitative summaries of heritabilities. When these were unavailable, we calculated weighted mean heritabilities from twin studies meeting modern methological standards.
Results Heritability summary estimates were as follows: bipolar disorder (85%), schizophrenia (81%), Alzheimer's disease (75%), cocaine use disorder (72%), anorexia nervosa (60%), alcohol dependence (56%), sedative use disorder (51%), cannabis use disorder (48%), panic disorder (43%), stimulant use disorder (40%), major depressive disorder (37%), and generalized anxiety disorder (28%).
Conclusions No systematic relationship exists between the disease-like character of a psychiatric disorder and its heritability; many behavioral disorders seem to be more heritable than conditions commonly construed as diseases. These results suggest an error in ‘common-sense’ assumptions about the etiology of psychiatric disorders. That is, among psychiatric disorders, there is no close relationship between the strength of genetic influences and the etiologic importance of volitional processes.
(Received May 26 2009)
(Revised March 28 2010)
(Accepted March 31 2010)
(Online publication May 12 2010)