HIGH work demands are to blame for more than 21,000 cases of depression in Victoria each year, according to a new Melbourne University study.

The study, led by the university's Associate Professor Tony LaMontagne, found that almost one in six cases of depression among working Victorians were caused by job stress.

Associate Professor LaMontagne said employers  including Prime Minister Kevin Rudd, who last week warned reportedly overworked public servants that they should expect their work load to only increase  must be mindful of the strain unreasonable work demands can have on workers' mental health.

He said unless moves were made to moderate job demands and provide support for supervisors and colleagues to better understand the problem, mental health issues would continue to put enormous pressure on the public purse through Medicare.

"(Jobs) can be challenging. I'm not talking about making it easy for everybody, people don't necessarily want that," Associate Professor LaMontagne, from the university's VicHealth Centre for the Promotion of Mental Health and Community Wellbeing, said.