Workers who are victims of bullying on the job may become more likely to contemplate suicide than people who don't experience a hostile office environment, a Norwegian study suggests.

Researchers surveyed a nationally representative sample of roughly 1850 workers and followed them from 2005 to 2010. While less than five percent of participants reported thoughts of suicide during the study period, they were about twice as likely to do so after being victims of workplace bullying.

"Our study adds to the understanding of how bullying is related to thoughts about suicide by showing that the perception of being bullied at work actually is a precursor of suicidal ideation and not a consequence," said lead study author Morten Birkeland Nielsen of the National Institute of Occupational Health and the University of Bergen.

At least 800,000 people worldwide take their own lives each year, making suicide a leading cause of death, Nielsen and colleagues write in the American Journal of Public Health.

Although psychiatric disorders are involved in the majority of suicide attempts, most people with mental health disorders don't take their own lives, the researchers note.

The relationship between bullying and suicidal thoughts is something of a "chicken and egg" problem, Nielsen told Reuters Health by email. It's difficult to determine which comes first.

In an effort to solve this riddle, Nielsen and colleagues surveyed workers in 2005, 2007 and 2010, asking about their work environment and mental health.

Researchers defined three main characteristics of workplace bullying: an employee must be the target of systematic unwanted social behavior; the exposure must occur over a prolonged period of time, often with increasing frequency and intensity; and targets feel they can't escape the situation or stop unwanted treatment.

Over the course of the study, the average proportion of workers reporting bullying ranged from 4.2 percent to 4.6 percent, while the prevalence of suicidal thoughts varied from 3.9 percent to 4.9 percent.

There were no major differences in reports of bullying or suicidal thoughts based on workers' gender or age.

While people who reported bullying early in the study were more likely to later report suicidal thoughts, the reverse didn't prove true. Workers who said they had contemplated suicide at the beginning of the study were no more likely to later report bullying than participants who had never considered killing themselves.

One limitation of the study is its reliance on participants to accurately recall and report any exposure to bullying or thoughts of suicide, the authors acknowledge.

"There are probably some workers who are more likely to consider suicide due to specific predispositions, whereas others are more likely to consider suicide due to their recent exposure to bullying," Nielsen said.

With prolonged exposure to bullying and other forms of distress, changes in the brain can occur, said Gary Namie, director of the Workplace Bullying Institute based outside Boise, Idaho. The brain can become flooded with glucocorticoids, commonly called stress hormones, which reduce capacity for clear, rational thinking, Namie, who wasn't involved in the study, said by email.

For at least some people, workplace bullying might be a tipping point toward considering suicide that mental health professionals may overlook, focusing instead on family or financial problems, Namie added.

The study findings suggest that the office problems merit a more serious look.

"Being bullied is one cause of thinking about taking one's life," Namie said. "Being bullied led to suicidal ideation and not the opposite - this is important for that reason."