A failure in the chemical messaging system in the brain has been identified in people with schizophrenia.
The researchers carried out hi-tech brain scans
A team from the UK's Institute of Psychiatry compared hi-tech scans of the brains of people with the condition with healthy volunteers.
They found a glitch at the chemical junction which needs to be negotiated for nerve cells to talk to each other.
The charity Rethink said the research was important, but added schizophrenia was "more than a chemical imbalance".
Schizophrenia affects around 1% of the population - as many as are affected by diabetes - and it often strikes young people as they aim to complete their education or begin work.
It is linked to disrupted thinking and behaviour, but scientists want to discover why that happens.
The IoP researchers, working with colleagues from University College London, used a scanning technique called single photon emission tomography (SPET).
They compared brains in 13 healthy people with five people with untreated schizophrenia and another 16 who were on medication for the condition.
When the communication system in the brain works properly, neurons talk to each other by sending out branches.
These branches connect at a junction where the chemical glutamate acts as a key to unlock a barrier - a chemical called NMDA receptor - and allow the message through.
A failure in this system leads to poor connections between areas of the brain that need to talk to each other.
The SPET scans allowed the researchers to check how the system was working by injecting a radiation-emitting chemical which seeks out working NMDA receptors.
The data was then processed and showed people with schizophrenia had fewer successful "dockings" in the left hippocampus area in the brain - an area known to be involved in learning, perception and memory - than healthy people.
However, those taking medication had relatively good results from the test.
The drugs appear to boost levels of glutamate, but are designed to target another chemical system in the brain.
However, that can lead to severe side effects such as chemically-induced Parkinson's disease.
Targeting the glutamate/NMDA system directly could be more effective, the researchers suggest.
Professor Lyn Pilowsky, who led the study, said: "What this intriguing finding means is that for the first time we may have a non-invasive method for scanning chemicals in the brains of living patients which may lead to new treatments and ways of diagnosing the disorder."
Paul Corry, of the mental health charity Rethink, said: "Schizophrenia is notoriously difficult to diagnose.
"Yet, providing people with the medical and social support as early as possible is crucial in ensuring the best possible hopes of recovering a full and meaningful life.
"Any research that enables the medical profession to get that support to people as early as possible is very welcome.
"However, it is important to understand that schizophrenia is much more than an imbalance of chemicals in the brain. It is profoundly affected by social factors such as poverty, early life experiences and trauma."