BRAIN waves could provide the first objective test for schizophrenia, a study has shown.
Measuring the magnetic field produced by electrical currents in the brain can identify patients with the mental disorder, scientists found.
Currently, schizophrenia can only be diagnosed by assessing a patient's symptoms and looking at their medical history.
The psychotic illness usually starts in late adolescence and can cause hallucinations, delusions, paranoia and social withdrawal.
Doctors diagnose schizophrenia by ticking off a defined set of symptoms, but during lucid moments patients can appear quite normal, and might even try to cover up their condition.
The non-invasive magnetoencephalogram (MEG) technique was used by British and Spanish researchers to compare individuals with schizophrenia and healthy individuals.
They found two specific signals that were significantly different in the psychotic patients.
In addition, four brain wave signals from the schizophrenia patients were found to change with age in a way not seen in healthy volunteers.
The findings are published in the journal Physiological Measurement.
Lead researcher Dr Javier Escudero, from the University of Plymouth, said: "At present, there is no blood, cerebrospinal fluid, brain imaging or neurophysiological test for schizophrenia in routine clinical practice. The diagnosis relies on the interpretation of symptoms and clinical history according to consensus criteria.
"The advent of an objective marker for schizophrenia would significantly facilitate the diagnosis and offer a better understanding of the neurobiological basis of the disease."
Scientists studied the frequency spectrum of the MEG background activity in 15 schizophrenia patients with positive symptoms and 17 age-matched healthy volunteers.
MEG readings were divided into five different groups representing different parts of the brain.
Patients undergoing an MEG examination place their head into a sensitive machine that picks up magnetic fluctuations produced by electrical activity in the brain.
It differs from an electroencephalogram (ECG), which measures electrical current directly, in that no electrodes are attached to the scalp.
Using the MEG signals, the researchers were able to classify patients with 71% accuracy.
"The long-term vision is to develop a low-cost, non-invasive and objective test to aid the diagnosis of this and other brain diseases," said Dr Escudero.
"The magnetoencephalogram is able to provide very detailed information about the brain activity; however, it is expensive. Therefore, we aim to transfer these developments to electroencephalogram recordings in the future, as this technique meets those requirements of reduced cost, high availability and non-invasiveness."