Schizophrenia is genetically complex but patterns are emerging

Genetic mutations implicated in autism and intellectual difficulties may also underlie schizophrenia, say researchers after a study comparing the DNA of schizophrenia patients with that of their parents.

Professor Mick O'Donovan, from Cardiff University, who co-led the research, said it suggested that several psychiatric and developmental disorders 'might share some common mechanisms and lends further weight to calls for research that integrates findings across multiple disorders'.

Previous studies have shown that common psychiatric disorders share genetic risk factors (see BioNews 695). Traditionally, however, research into these conditions has been guided by the clinical picture, where, for example, autism and schizophrenia are seen as very different, possibly entirely unrelated disorders.

The study looked at the DNA of 623 Bulgarian schizophrenia patients and compared it with their parents' DNA. The scientists were particularly interested in 'de novo' mutations - genetic mutations that are found in affected people but not in their parents.

They identified de novo mutations that appeared to be linked to schizophrenia and compared their results with previous similar studies on autism and intellectual disability. There was considerable overlap.

Many of the affected genes work in pathways involved in establishing and maintaining connections between nerve cells and are important for brain development.

Professor Mike Owen, also a study co-lead at Cardiff University, said: 'For the first time we have a handle on one of the core brain processes that is disrupted in the disorder'.

The study was published alongside another in the journal Nature, in which scientists looked at the genes of over 2,500 people with schizophrenia, and a similar number of controls. Both studies suggest that rather than being explained by a single 'schizophrenia gene', a large number of rare genetic mutations contribute to risk for the disease.

The two studies are among the largest DNA sequencing studies to be performed on schizophrenia.

Dr Shaun Purcell, head of the Center for Statistical Genetics at Mount Sinai Hospital in New York, who led the second study, admitted that 'the complexity of the genetics is sobering' but the work should help researchers develop better treatments 'than the one-size-fits-all approach currently used'.

Schizophrenia is one of the most common serious mental health conditions, affecting about one percent of the population at some point in their lifetime. The exact cause is unknown but many scientists think it emerges through a combination of genetic predisposition and environmental factors.