The firm has compiled a league table of tough jobs, measuring their impact on physical health, psychological well-being, and job satisfaction.
At the other end of the scale senior business directors were found to be the least stressed. The researchers say this is because while they face pressure to perform business-wise their lack of front-line direct contact with customers or the public leaves them less stressed.
The research also suggests the most stressful jobs involve direct contact with the public in emotionally intense situations, where the working environment is governed by strict rules. There is also evidence that, in the main, a boss' job is much less stressful than a worker's.
Unison represents staff in members of the most stressed-out jobs, and has long been campaigning for more attention to be paid to work-life balance and support for those facing stress in their jobs.
'Stress is one of the biggest health issues faced by our members in health and social care work, and the research supports this view,' said Unison national health and safety officer Hope Daley.
'It is time employers recognised the cost of stress to their workforce, business and society because of their inability or unwillingness to tackle the factors that cause it. Stress is a major contributor to work-related illness, but sickness absence and the introduction of punitive measures to reduce these absences continue to be introduced in both the health and social care sector - yet many employers fail to see a link.
'Our message is reduce stress and you will reduce the number of days lost through sickness.'