Psychotic patients are more likely to be obese and at a higher risk of becoming smokers and victims of alcohol abuse than the general population, a new study released on Wednesday by Australia's mental health charity SANE found.

A snapshot of 2,000 Australians with psychotic illnesses, including schizophrenia and bipolar disorder, found most were in poor physical shape.

According to findings from the study, almost half of all Australians with a psychotic illness are obese, two thirds smoke and over half have problems with alcohol and other drugs abuse.

People with psychotic illness are rarely physically active and often have a poor diet.

SANE Executive Director Barbara Hocking said patients who were in poor physical shape were at risk of developing diabetes, cardiovascular disease and other health problems.

"It's not a pretty picture," she said.

"It's tough enough managing mental illness but if you have to manage something like diabetes or heart problems, that's doubly difficult."

SANE estimates at least 64,000 Australians are affected by a psychotic illness, with symptoms such as delusions, hallucinations, anxiety and depression.