New research has revealed that two neurotransmitters-dopamine and glutamate-are abnormal in people with psychotic illness, including schizophrenia.
Among many other things, these chemicals play a role in cognitive functions, such as memory, learning, and problem solving.
James Stone and colleagues studied people with sub-threshold psychotic symptoms, who were at very high risk of undergoing transition to full-blown psychotic illness, using two brain imaging techniques - magnetic resonance spectroscopy, which allows measurement of glutamate in the brain, and [18F]DOPA positron emission tomography, which gives a measure of dopamine neuron activity.
They found that in these individuals, lower glutamate in hippocampus, a major structure in the brain involved in memory, was associated with increased dopamine activity.
This was in keeping with earlier animal models, and with clinical studies of hippocampal and striatal function in psychosis.
According to Stone, "the findings support the hypothesis of an abnormal relationship between the dopamine and glutamate neurotransmitter systems in individuals with psychosis, and suggest that the development of drugs targeting glutamatergic transmission may be useful in the early treatment of psychosis."
The findings also suggested that this abnormal glutamate-dopamine relationship might be a risk marker for later transition to a psychotic disorder.
The findings were published in Biological Psychiatry.