Nearly 34 per cent of respondents to a mental health survey answered "yes" to the question "have you ever suffered from or been diagnosed with, mental ill health?".
Figures from the Office for National Statistics for the general population in 2007 found that one in four people had experienced mental ill health in any given year.
Just over 60 per cent of those surveyed by the PRCA said they would feel either "not very comfortable" or "very uncomfortable" discussing a mental health condition with their boss or a colleague.
However, 42 per cent of respondents said a colleague had discussed a mental health issue with them in the past.
Of the 430 people who took part in the survey, 60 per cent said the industry was either "not very accepting" or "very un-accepting" of the issue of mental health.
And 44 per cent of those surveyed said they were more stressed at work than last year, while 22 per cent reported less stress and 30 per cent said stress levels were the same.
Respondents told the survey the chief causes of stress in the industry were the workload, pressure from clients and the senior team, unrealistic demands and a lack of support from line managers.
Francis Ingham, director general of the PRCA, said he was concerned by the survey findings.
He added: "It appears that stress can be a factor in this busy and successful industry. This needs to be addressed at both an industry-wide level and at each agency and in-house team, by keeping in mind whether employees are receiving the right levels of support and guidance as they carry out their work."