A slight but noticeable loss of brain volume among patients with schizophrenia taking antipsychotic drugs doesn’t appear to affect cognitive functioning, European researchers say.

A long-term study of 33 patients with schizophrenia, along with 71 control subjects for comparison, confirmed that those taking antipsychotic drugs lost brain volume more quickly than average through the aging process. Whereas study subjects in the control group lost brain volume at a rate of 0.5 percent per year over a nine-year period, patients treated with antipsychotic drugs for schizophrenia lost 0.7 percent per year — consistent with the average cognitive aging process for someone aged 34 to 43.

The findings were published in the journal PLOS One by researchers from the University of Oulu, Finland, and the University of Cambridge.

"It's important to stress that the loss of brain volume doesn't appear to have any effect on people over the nine year follow-up we conducted, and patients should not stop their medication on the basis of this research," said Graham Murray, a researcher at Cambridge, in a statement. "A key question in the future will be to examine whether there is any effect of this loss of brain volume later in life. We need more research in larger studies with longer follow-ups to evaluate the significance of these brain changes."

Murray said the study confirms suspicions among scientists that antipsychotic medication for schizophrenia is associated with a loss of brain volume, adding that greater loss was observed in patients whose doses were higher. However, the research team remains unsure whether the medication indeed causes the decrease in tissue, noting that some researchers believe newer classes of antipsychotic medications may confer the opposite effect: protecting the brain from loss of tissue.

Juha Vijola, a researcher from the University of Oulu, says the study at least demonstrates an association. "We all lose some brain tissue as we get older, but people with schizophrenia lose it at a faster rate. We've shown that this loss seems to be linked to the antipsychotic medication people are taking. Research like this where patients are studied for many years can help to develop guidelines about when clinicians can reduce the dosage of antipsychotic medication in the long-term treatment of people with schizophrenia."

Some 1.1 percent of the U.S. population has schizophrenia, according to the National Institute of Mental Health.

Source: Veijola J, Guo J, Moilanen J, et al. Longitudinal Changes in Total Brain Volume in Schizophrenia: Relations to Symptom Severity, Cognition and Antipsychotic Medication. PLoS One. 2014.