The healthcare specialist surveyed more than 2,000 workers in the UK last November and found that occupational stress kept 51% of workers awake at night, while 42% said it "ruined their life".
Stress was also found to cause physical sickness. More than half of the workforce (53%) reported that a poor work-life balance made them feel unwell, and a similar number (52%) said that work made them more unwell that anything in their personal lives.
Almost two thirds (64%) of respondents believed they would be significantly more productive at work if they were less stressed, while 76% said they had seen a colleague leave their place of work due to a lack of support.
They said they found workplace demands, such as presenting at an important meeting (71%) or managing a project (65%), as stressful as buying their first home (69%) or getting married (66%).
The majority (83%) of respondents said they expect their employers to do all they can to support their health and wellbeing, while 73% believed their employers could do more to support staff who have a mental or physical health issue.
Patrick Watt, corporate director at Bupa UK, said: "I'm happy to say thousands of businesses of all sizes are addressing this issue with their own people. But in doing so, they are recognising that the key challenge is no longer lack of awareness, but tackling stigma.
"As ever, prevention is as important, if not more, in tackling awareness and stigma associated with mental wellbeing conditions. From my experience, I know that workers are now more in touch with issues surrounding mental health and have increasing expectations that their employer will provide an environment which support their wellbeing.
"So, creating an environment where people feel confident talking about and accessing mental wellbeing services is as important from a productivity perspective as it is in attracting and retaining new talent."