New York (PTI): Scientists in the United States have uncovered rare and genetic glitches which they claim is a major step towards solving the puzzle of schizophrenia.

They have found that deletions and duplications of DNA are more common in people with the mental disorder and many of those errors occur in genes related to brain development and neurological function.

Schizophrenia is a disease of disordered thinking and behaviour. Patients have trouble organising their thoughts or communicating sensibly and many have either auditory or visual hallucinations.

"Take away schizophrenia's hallucinations and delusions and the symptoms that remain, the lack of social interest and withdrawal, are what we call autism. There is clearly an intersection of the brain systems involved," the study's lead author Jon McClellan said.

McClellan of the University of Washington and his colleagues at Cold Spring Harbor Labs examined whether the genetic errors, which are individually rare DNA deletions and duplications, contribute to the development of schizophrenia.

Some deletions and duplications are common and found in all humans. The researchers studied such mutations that were found only in individuals with the illness, and compared them to mutations found only in healthy persons.

They theorised that rare mutations found only in schizophrenic patients would be more likely to disrupt genes related to brain functioning and thus may cause schizophrenia.

The study was conducted using DNA from 150 people with schizophrenia and 268 healthy individuals. The researchers found rare deletions and duplications of genes present in 15 per cent of those with schizophrenia, versus only five per cent in the healthy controls.

The rate was found to be even higher in patients whose schizophrenia first presented at a younger age, with 20 per cent of those patients having a rare mutation, the 'ScienceDaily' reported.

The results were replicated by a second research team at the National Institute of Mental Health. They also found a higher rate of duplications or deletions in patients whose schizophrenia began before age 12 years, a very rare and severe form of the disorder.

"The findings suggest that schizophrenia is caused by many different mutations in many different genes, with each mutation leading to a disruption in key pathways important to a developing brain," according to the researchers.