Researchers Report Two Gene Loci Associated With MDD

Researchers have made important strides in recent years in finding genetic loci associated with risk for schizophrenia and autism, but similar steps in depression have remained more elusive.

Now, a group of scientists have reported that a study comparing 5,303 Han Chinese women with recurrent major depressive disorder (MDD) with 5,337 controls revealed two loci on chromosome 10 that contribute to risk of MDD. The findings, published online today in the journal Nature, are the work of Kenneth Kendler, M.D., a professor of psychiatry at Virginia Commonwealth University School of Medicine in Richmond, and other U.S., British, and Chinese colleagues from the CONVERGE consortium.

The team found that one locus lies near the SIRT1 gene and the other in an intron of the LHPP gene. The findings were replicated in a separate cohort of more than 6,000 Han Chinese men and women (including 3,231 cases of recurrent MDD). When the analysis was limited to those with melancholia, a more severe form of MDD, it yielded an increased genetic signal at the SIRT1 locus.

“MDD is most probably highly polygenic, and many additional loci remain to be discovered,” the researchers wrote. “We attribute the discovery and replication of two SNPs associated with MDD in the CONVERGE cohort to the recruitment of cases who were probably more homogeneous and more severely impaired than those collected in previous studies from Western cultures.”

For more in Psychiatric News on psychiatric genetics, see “Revolution in Psychiatric Genetics Rapidly Gains Steam.”

--aml (Image: Vitstudio/Shutterstock.com)

Common Genetic Variation May Underlie Different Mental Illnesses

An international group of psychiatric researchers has identified a 15% overlap between schizophrenia and bipolar disorder in heritability attributable to common genetic variation, according to a study by the Cross Disorders Group of the Psychiatric Genomics Consortium, published online in Nature Genetics August 11.

The group of more than 300 researchers in 20 countries used genomewide genotype data from thousands of people and compared them with control subjects. Besides the relationship between schizophrenia and bipolar disorder, there was a 10% overlap in heritability between bipolar disorder and depression, a 9% overlap between schizophrenia and depression, and a 3% overlap between schizophrenia and autism. The common genetic variants with small effects revealed in this and related studies will eventually be supplemented by other research on other variations.

“Shared variants with smaller effects, rare variants, mutations, duplications, deletions, and gene-environment interactions also contribute to these illnesses,” said study co-leader Naomi Wray, Ph.D., of the University of Queensland in Australia, in a statement accompanying the study. “Since our study only looked at common gene variants, the total genetic overlap between the disorders is likely higher.”

The study was funded in part by the National Institute of Mental Health.

Read more about the work of the Psychiatric Genomics Consortium in Psychiatric News here.

(Image: Carlos Gardel/Shutterstock.com)

Schizophrenia in Families May Be Risk Factor for Autism

There is some evidence of overlap between autism spectrum disorder (ASD) and schizophrenia, but studies testing that hypothesis have been small and produced mixed results. But now, a large study using Swedish population and patient data suggests that a family history of schizophrenia or bipolar disorder might be a risk factor for ASD.

The researchers compared data from more than 25,000 cases of patients with ASD with data from control subjects. Patients with ASD were 2 to 3 times more likely to have a parent or sibling with schizophrenia and about 1.5 to 2 times more likely to have one with bipolar disorder, reported Patrick Sullivan, M.D., of the Department of Genetics at the University of North Carolina at Chapel Hill, and colleagues in the November Archives of General Psychiatry. “Our findings indicate that ASD, schizophrenia, and bipolar disorders share etiologic risk factors,” the researchers said, "factors common to these disorders.”

To read more about this study, see Psychiatric News here. For a comprehensive review of autism etiology, diagnosis, and treatment, see Textbook of Autism Spectrum Disorders from American Psychiatric Publishing. 

(Image: Marcin Pawinski/Shutterstock.com)

Grandfather’s Age Raises Risk of Schizophrenia

Scientists have known for years that the children of older fathers have a greater risk of developing schizophrenia than children of younger fathers. Now researchers led by Christina Hultman, Ph.D., of the Karolinska Institutet in Stockholm have confirmed that finding and added to it: the same effect was seen in children whose maternal (but not paternal) grandfathers were over 55. That suggests that a mechanism involving the X-chromosome (women have two X-chromosomes, men have one X- and one Y-chromosome) may have some relationship with the link between a father’s age and the child’s risk of schizophrenia. For more about risk factors and schizophrenia, see Psychiatric News.

(Image: Yuri Arcurs/Shutterstock.com)