Australasian Science: Australia's authority on science since 1938

Genetic Overlap in Mental Illnesses

By Stephen Luntz

Genetic variations associated with depression, schizophrenia and bipolar disorder have substantial overlap, indicating possible relationships between the conditions.

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“We studied the genetic information of more than 75,000 people using a type of genetic variation called single nucleotide polymorphisms (SNPs),” says A/Prof Naomi Wray of the University of Queensland’s Brain Institute. “A SNP is one of the most common genetic changes, and involves the replacement of a single unit that makes up our DNA with another. Using about a million SNPs measured on each person, we found evidence of increased genetic similarities between people with the same disorder.”

The SNPs studied accounted for around 20–25% of the variation in rates of these diseases, or about one-third of the total genetic contribution. “The rest could be from rarer SNPs or from other genetic effects,” Wray says. “Our research is consistent with the idea that the genetic component is high.”

While the SNPs of someone suffering from a particular condition had more in common with the SNPs of others with the same condition than with people suffering from other diseases, there was considerable overlap between schizophrenia, bipolar disorder and depression.

Initial misdiagnosis of mental illness is common. “I was worried that this could affect our data, so I investigated and published another paper showing that even at common levels of misdiagnosis this could not account for the overlap we observed,” Wray says. She also believes the patients included in the study...

The full text of this article can be purchased from Informit.