Connections found between ancient viruses in the human genome and mental health disorders

An ancient virus that became embedded in human DNA millions of years ago may play a role in increasing people's risk of depression, schizophrenia, and bipolar disorder. Studies have found that people at high genetic risk of experiencing these mental health conditions have abnormal levels of viral gene activity.

Retroviruses are a large group of viruses whose life cycle involves the insertion of genetic information into the DNA of their host. Such viral genetic remnants are found in the DNA of many animal species, and when these sequences are found in the human genome they are called human endogenous retroviruses (HERVs).

Until recently, most HERVs were thought to be dormant and were called “fossil viruses,” but previous studies have suggested that some of the viral genes may actually be active, without producing infectious virus, and may even be involved in neurological symptoms. such as multiple sclerosis.

In the new study, Timothy Powell Researchers from King's College London investigated the possible role of these viral remnants in mental health conditions by examining viral proteins in around 800 brains donated for medical research.

Although the team did not record whether the donors had been diagnosed with any psychiatric illnesses during their lives, they found that some of the genetic variants known to increase the risk of depression, schizophrenia, and bipolar disorder were associated with changes in the activity of five different HERV genes.

Powell said he couldn’t estimate how much of the increased risk was linked to abnormal viral gene activity, but it’s probably in the range of a few percent because most human gene mutations only have a small effect on mental illness risk.

The findings also don’t necessarily mean that changes in HERV activity are causing the symptoms, he says, which could be a consequence.

“The method used appears to be very robust” Rachel Turlington “It is likely true that these things are markers for these diseases, but [the researchers] I’m understandably cautious to say I don’t know what that means.”