Scientists have identified dozens of genes that work differently in the brains of people with schizophrenia, a finding that could narrow the search for new drugs to treat the condition, researchers said on Tuesday.

Many of these 49 genes found in brain samples donated by people with schizophrenia are involved in controlling the way cells "talk" to each other, suggesting faulty signalling between them could cause the condition, they said.

"We are getting closer to seeing what is going wrong in schizophrenia and this very specifically tells us what to target for drug treatment," Jackie de Belleroche of Imperial College London, who led the study, said in a telephone interview.

"The first step toward better treatments for schizophrenia is to really understand what is going on, to find out what genes are involved and what they are doing."

Schizophrenia, characterised by hallucinations, delusions and disordered thinking, is far more common in men than in women and is usually diagnosed in late adolescence or early adulthood. It affects around an estimated one in 100 people.

While anti-psychotic drugs such as AstraZeneca's Seroquel and Eli Lilly and Co's Zyprexa can help, such drugs do not cure the mental illness and can cause unpleasant side-effects, including sometimes dangerous weight gain.

Some research indicates the condition occurs when the brain produces too much of a chemical called dopamine while another theory is that the coat surrounding nerve cells is damaged in people with schizophrenia, de Belleroche and colleagues said.

The team from Imperial College London and GlaxoSmithKline Plc analysed brain tissue donated by 23 healthy people and 28 men and women with schizophrenia. Then they compared the samples to a similar sized group in the United States.

This revealed 49 genes that worked differently in the samples of people with schizophrenia, suggesting that abnormalities in the way in which cells signal each other are involved in the disease, the researchers said.

The findings could also lead to new ways, such as blood tests for certain markers or more specific brain imaging, to help doctors diagnose schizophrenia earlier than waiting for a person's behaviour to change, de Belleroche added.

"Most patients are diagnosed as teenagers or in their early 20s, but if they could be diagnosed earlier, they could be treated more effectively and they could have a better quality of life," she said.