As a group, people with schizophrenia appear to be genetically predisposed to start smoking and to smoke more cigarettes per day, according to a genomic analysis that examined the relationship between schizophrenia and several risk factors for cardiovascular disease. The findings were published today in The American Journal of Psychiatry.
“Schizophrenia is associated with a two- to threefold greater risk of [cardiovascular disease] compared with risk in the general population, contributing to a 10- to 20-year reduced life expectancy,” wrote Linn Rødevand, Ph.D., of the Norwegian Center for Mental Disorders Research at the University of Oslo and colleagues. While some of this risk is believed to be the result of lifestyle factors (for example, smoking) and limited access to health care, research also suggests that the genetic makeup of some individuals with schizophrenia may increase risk of cardiovascular disease.
To understand the genetic overlap between schizophrenia and risk factors for cardiovascular disease, Rødevand and colleagues analyzed data from genomic-wide association studies (GWAS). GWAS is a research approach used to identify genomic variants that are associated—either positively or negatively—with a risk for a disease or a particular trait.
Results for schizophrenia were retrieved from the Psychiatric Genomics Consortium, consisting of 53,386 patients with schizophrenia and 77,258 control participants of European descent. GWAS data on risk factors for cardiovascular disease included millions of people and looked at such factors as smoking initiation, number of cigarettes smoked per day, body mass index (BMI), type 2 diabetes, blood pressure, and more.
In addition to risk for smoking and number of cigarettes smoked per day, genetic overlap was found between schizophrenia and other risk factors, such as BMI. However, people with schizophrenia were found to be genetically predisposed to lower BMI on average—despite obesity being more common in individuals with schizophrenia compared with those in the general population. This strongly suggests the influence of environmental factors, including the effects of antipsychotic drugs and socioeconomic challenges that contribute to unhealthy lifestyles, on the prevalence of obesity among patients with schizophrenia.
“Studies with larger GWASs will uncover more of the genetic architecture of schizophrenia and may reveal differences in genetic liability to [cardiovascular disease] across subsets of patients,” the researchers wrote. “Such findings could provide clinically useful discoveries that pave the way for risk stratification and more tailored interventions.”
For related information, see the Psychiatric News article “Psychiatrists Can Do More to Help Patients Quit Smoking.”
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