Schizophrenia and Bipolar Disorder Share Around 70% of Their Genetic Signal, Major Study Finds

Schizophrenia and bipolar disorder share around 70% of their genetic signal, a recent study has found.

Schizophrenia and bipolar disorder, two psychiatric conditions diagnosed and treated as distinct illnesses, may have much more in common at the genetic level than previously thought.

This is the conclusion of a study published in the scientific journal Nature, in which researchers analysed genetic data from 1,056,201 people with 14 different psychiatric disorders, comparing them with data from millions of other people.

The researchers did not find a completely distinct genetic pattern for each disorder.

Instead, the analysis identified five main genetic clusters, which explained on average around 66% of the genetic variation linked to the disorders analysed.

One of these clusters brought together schizophrenia and bipolar disorder.

According to the study, around 70% of the genetic signal linked to schizophrenia was also linked to bipolar disorder.

The researchers called this cluster the “schizophrenia–bipolar” factor and found relatively few genetic regions that were specific to only one of these two disorders.

What does “genetic signal” mean?

With this term the researchers do not mean a single gene that causes the illness.

It refers to many small changes in DNA which, taken together, are linked to a higher or lower risk of a disorder.

The 70% figure shows how much the genetic factors identified in the analysis overlap — not the probability that a person with schizophrenia will also develop bipolar disorder.

Link to brain cells

The researchers also found that the genetic signal shared between schizophrenia and bipolar disorder was particularly linked to excitatory neurons.

Neurons are nerve cells that transmit information in the brain.

Excitatory neurons are a type of nerve cell that helps activate and transmit signals in brain networks.

This suggests that some of the biological mechanisms influencing both disorders may be linked to how these cells function and communicate with each other.

Other disorders also showed similarities

Schizophrenia and bipolar were not the only disorders that emerged as genetically linked.

The study also identified a cluster that included major depression, anxiety and post-traumatic stress disorder (PTSD), as well as another group covering neurodevelopmental disorders, including autism and ADHD.