Medications commonly used to combat physical health diseases, such as high blood pressure, could bring significant benefits to people with serious mental illnesses such as schizophrenia and bipolar disorder, a study claims.

The study, published in the journal JAMA Psychiatry, assessed the health data records of 142,691 patients with serious mental illness (SMI) in Sweden.

It focused on those patients who had either been prescribed Hydroxylmethyl glutaryl coenzyme A reductase inhibitors (HMG-CoA RIs), more commonly known as statins -- which are used to reduce cholestero, L-type calcium channel antagonists (LTCC), used to reduce high blood pressure, or biguanides (such as metformin), used to treat diabetes.

Researchers from Karolinska Institute in Sweden and University College London (UCL) in the UK analysed patients' health records relating to self-harm and psychiatric hospitalisation.

They assessed whether these episodes occurred during a period when patients were taking the prescribed medication or in periods when they were not.

The study found that exposure to any of the study drugs was associated with reduced rates of psychiatric hospitalisation compared with unexposed periods.

Self-harm was reduced in patients with bipolar disorder and schizophrenia during exposure to all study drugs and in patients with non-affective psychosis taking L-type calcium channel antagonists.

"Serious mental illnesses, including bipolar disorder, are associated with high levels of morbidity and are challenging to treat," said Joseph Hayes from UCL.

"Many widely used drugs, such as statins, have long been identified as having the potential for repurposing to benefit these disorders," said Hayes.

"This study is the first to use large population data sets to compare patient's exposure to these commonly used drugs and the potential effects on people with serious mental illnesses," he said.

All the studied drugs are known to have an effect on the central nervous system; however, the mechanism of action is not well understood and researchers believe a clearer understanding of this may lead to new drug development to benefit those with SMI.

"All three studied drugs are globally licensed, commonly used, cheap, and relatively safe medications. They are therefore ideal candidates for repurposing," Hayes said.