The study tested the effects of lithium, a mood stabiliser introduced in the 1970s, compared with those of quetiapine, now a more commonly prescribed alternative, on patients who had had a manic episode for the first time.
Lead researcher Professor Michael Berk, Director of Deakin's Centre for Innovation in Mental and Physical Health and Clinical Treatment at Barwon Health, said lithium seemed to be better than quetiapine in protecting the brain after a first episode of illness.
Professor Berk said it was important to independently test the effectiveness of mental health medications, as sometimes their popularity was affected by factors outside of successful treatment.
"Mood stabilisers are the mainstay of treatment of bipolar disorder and are essentially used to keep people well," he said.
"The oldest drug we have is lithium, but there are some new contenders, principally medicines called atypical antipsychotics, which are usually used for schizophrenia, and quetiapine is one of the best examples.
"Lithium has a lot of side effects and the newer agents have gained traction such that they have become first-line and widely used treatments.