Employees subjected to real or threatened violence at work run a major risk of becoming clinically depressed, indicates research in the Journal of Epidemiology and Community Health.
The magnitude of the risk was in direct proportion to the amount of workplace violence experienced, the study shows.
The findings are based on the occupations of more than 14,000 hospital patients between the ages of 18 and 65, who were being treated for depression or stress related disorders between 1995 and 1998.
These patients were then compared with 38, 000 people without mental ill health problems, but matched for age and sex. All participants were asked about their jobs and if they had been subjected to violence at work in the previous 12 months.
The prevalence of real and threatened violence was highest among those working in health, education, and social work sectors. Male employees were at greater risk of violence than women.
While most violence came from clients, patients, and pupils, around 5% of study participants with mental health problems said they were subjected to violent behaviour from their work colleagues.
Almost half said they had been subjected to more than one incident of violence or threatening behaviour in the preceding 12 months, and one in five said they had been subjected to both.
Exposure to violence boosted the risk of depression by 45% in women and 48% in men, compared with those in workplaces without any risk of violence.
Stress related disorders were around a third more likely in women and 55% more likely in men.
Threatening behaviour boosted the likelihood of depression by 48% in women and stress related disorders by almost 60% in men.
The magnitude of risk was directly proportional to the amount of violence experienced at work.
The authors say that other research suggests that being subjected to violence may over stimulate the autonomic nervous system, which then translates into an emotional disorder, even among those with stable personality traits.
The risk of psychiatric problems among employees exposed to violence is well recognised and reflected in guidance from the European Commission and the International Labour Organisation, they add.
"Despite these efforts, there seems to be no decrease in work related violence, threats, and harassment," they conclude.