Mapping Mental Disorders

A new study by an international team of researchers published last Thursday in the journal Science has got one step closer to understanding the genetic component to mental illness.

Linking psychiatric disorders and genetics is fraught with difficulties, with still much research to undertake. Due to sporadic symptoms and the nature of mental disorders, diagnosis can often be difficult or incorrect. For example, the difference between depression and bipolar disorder may not be apparent to psychiatrists immediately, and there are no diagnostic tests to distinguish this.

A new study by an international team of researchers published last Thursday in the journal Science has got one step closer to understanding the genetic component to mental illness. The large-scale analysis used 700 post-mortem patient brains of the five major psychiatric disorders: autism, schizophrenia, bipolar disorder, depression and alcoholism, compared to controls. It found that there are shared and distinct patterns of gene expression across the disorders and further suggested that the shared genetic factors were acting indirectly through developmental and cell-signalling events.

The work, led by Dan Geschwind – a neuroscientist at UCLA – and his colleague Michael Gandal, looked specifically at expression patterns from the cerebral cortex (the brain’s outer layer). The results showed that some diseases appear more similar genetically than others. For example, bipolar and schizophrenia cortical gene activity overlapped and both conditions presented similar active genes. However, the genes were found to be more active in autism, suggesting overexpression may play a role in the manifestation of the disorder. Neuronal firing genes were also seen to be underexpressed in autism, schizophrenia and bipolar disorder, indicating that cell communication in the brain is important in all three conditions.

Additionally, the microglia, a subset of brain immune cells, were found to be overactive in autism. As a result, Gandal is now heading a clinical trial to investigate whether antibiotics could help regulate these cells in adult autism. This study can also provide a framework for future studies into molecular signalling pathways and disease risk.