Family genetic risk scores show separations between major affective, psychotic disorders
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Family genetic risk scores showed clear separations between major affective and psychotic disorders and were linked to early age at onset and high rates of recurrence, according to results of a Swedish cohort study published in JAMA Psychiatry.
“We sought to clarify from a genetic perspective, in a true national sample, the relationship between major psychotic and mood disorders,” Kenneth S. Kendler, MD, of the Virginia Institute for Psychiatric and Behavioral Genetics at Virginia Commonwealth University, told Healio Psychiatry.
Specifically, Kendler and colleagues aimed to assess whether family genetic risk scores for the entire Swedish population were able to demonstrate the genetic relationship between major affective and psychotic disorders, as well as to clarify the link between genetic risk and significant clinical features of disease. They included 4,129,002 individuals (mean age at follow-up, 45.5 years) born in Sweden between Jan. 1, 1950, and Dec. 31, 1995, and conducted follow-up until Dec. 31, 2017. They obtained data via Swedish population-based primary care, specialist and hospital registers, which included age at first psychiatric diagnosis registration and number of registrations for major depression, bipolar disorder and schizophrenia. Family genetic risk scores for major depression, bipolar disorder and schizophrenia, which the researchers calculated using morbidity risks for disorders among first- through fifth-degree relatives and for which they controlled for cohabitation, served as exposures.
Results showed distinct patterns for major depression, bipolar disorder, schizophrenia and schizoaffective disorder resulting from mean family genetic risk scores for major depression, bipolar disorder and schizophrenia. The researchers noted other nonaffective psychoses had large separations between disorders. High family genetic risk scores in major depression, bipolar and schizophrenia were linked to early age at onset and high recurrence rates, with a high mean family genetic risk score for bipolar disorder tied to onset at ages younger than 25 years and higher recurrence with eight or more registrations in major depression. Kendler and colleagues observed a separate association between schizophrenia family genetic risk score and nonpsychotic forms of major depression and bipolar disorder. Family genetic risk scores for bipolar disorder and schizophrenia were linked to conversion from major depression to bipolar disorder and other nonaffective psychoses to schizophrenia.
“These findings make clear how genetic risk factors can impact both the diagnosis and then features of the disorder, such as age at onset and presence of psychotic symptoms, in those with bipolar disorder or major depression,” Kendler said.