Antipsychotic medication may lead to a slight decrease in brain volume, according to a recent study.

Researchers from the University of Oulu, Finland, and the University of Cambridge have identified the rate of decrease in both healthy individuals and patients with schizophrenia. They also documented where in the brain schizophrenia patients have more atrophy, and have examined links between atrophy and antipsychotic medication.

As we age, our brains naturally lose some of their volume - in other words, brain cells and connections. This process, known as atrophy, typically begins in our thirties and continues into old age. Researchers have known for some time that patients with schizophrenia lose brain volume at a faster rate than healthy individuals, though the reason why was unclear.

For the study, researchers compared brain scans of 33 patients with schizophrenia with 71 control subjects over a period of 9 years -- from age 34 to 43 -- the researchers were able to show that schizophrenia patients lost brain volume at a rate of 0.7 percent each year. The control participants lost brain volume at a rate of 0.5 percent per year.

Researchers said scientists have previously speculated that antipsychotic medication used to treat schizophrenia may be linked to this decrease in brain volume. Today's research confirms this association, showing that the rate of decrease in volume was greater when the dose of medication was higher.

However, the mechanisms behind this - and whether it was in fact the medication that was causing this greater loss of tissue - are not clear.

In the study, the researchers also looked at whether there was any link between the volume of brain lost and the severity of symptoms or loss of cognitive function, but found no effect.

"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," professor Juha Veijola said in a statement. "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."

The findings were recently published in the open access journal PLOS ONE.