EEG delta/alpha frequency activity can be used to differentiate patients with schizophrenia, bipolar disorder, and methamphetamine-induced psychotic disorder, researchers from South Africa report.
"A simple EEG system has the potential to diagnose the different presentations of psychotic disorders, which often requires extensive observation by clinicians before consolidating the final diagnosis," Dr. Fleur M. Howells of the University of Cape Town told Reuters Health by email.
Increased EEG delta activity (delta synchronization) and decreased alpha activity (alpha desynchronization) have been reported in schizophrenia and bipolar disorder, Dr. Howells and colleagues note in Translational Psychiatry, but there are no studies in methamphetamine-induced psychotic disorder (MPD).
The researchers investigated EEG activity using delta/alpha ratio as a potential biomarker in psychosis in 28 individuals with schizophrenia, 28 with bipolar disorder, 24 with MPD and 29 healthy controls.
During resting with eyes closed, delta/alpha-frequency activity was significantly higher in individuals with schizophrenia and MPD than in controls. And the MPD delta/alpha-frequency activity was higher compared with bipolar disorder for the right hemisphere.
When participants were at rest with their eyes open, delta/alpha-frequency activity was higher in all three psychotic disorders than in controls.
During a continuous-performance task, bipolar disorder and MPD delta/alpha frequency activity was higher than controls.
Second-generation antipsychotic medication lowered delta/alpha frequency activity globally during the cognitive task, most notably in the schizophrenia group.
"This data is preliminary," Dr. Howells said. "The next step is to significantly increase the number of research participants, include individuals with other psychotic disorders (and) research participants in their active states of illness."
"If I am able to show that these data are reliable and robust," she said, "we will be able to deploy simple EEG systems that are able to provide support in the diagnosis of psychotic disorders, which will improve patient management, ergo improve prognosis and quality of life for the individual suffering."
Dr. Thomas Reilly from King's College London's Institute of Psychiatry, Psychology and Neuroscience, told Reuters Health by email, "EEG is currently an important research tool for investigating the brain abnormalities underlying psychosis. It has excellent temporal resolution (milliseconds), measures brain activity directly, is cheap, well tolerated and repeatable.
"We don’t know yet if it will have any utility at the level of an individual patient," said Dr. Reilly, who was not involved in the new work. "At present, the best way to diagnose psychotic disorders is still through clinical assessment (especially history and mental state examination) with the judicious use of investigations. For example, a urinary drug screen is the best way to differentiate between methamphetamine-induced psychosis and schizophrenia - without the need for an EEG!"
"Advances in research could eventually lead to EEG being used to determine the treatment and prognosis of patients experiencing an episode of psychosis," Dr. Reilly said.
"It would be interesting to find out whether delta / alpha ratio predicts response to treatment in patients or long-term outcome," he added. "I would be especially keen to find out whether delta / alpha ratio could predict onset of psychosis in individual who are 'at risk."