High levels of job stress may increase the risk of sick leave due to mental health disorders, a new study suggests.

Researchers analyzed data from nearly 12,000 workers in Sweden. Over five years, about 8 percent of the workers took mental health sick leave.

Three-quarters of those who took mental health sick leave were women.

Workers with demanding jobs, high job strain and little social support at work were at greater risk for mental health sick leave, as were those with unhealthy lifestyles.

Smoking was a significant risk factor for mental health sick leave, but alcohol use was not.

High levels of physical activity reduced the risk of mental health sick leave, according to the study in the August issue of the Journal of Occupational and Environmental Medicine.

The findings add to previous research showing that psychological conditions in the workplace affect rates of mental health sick leave, and may suggest ways to reduce the risk, according to researcher Lisa Mater of the Karolinska Institutet in Stockholm, and colleagues.

"Interventions to reduce sick leave due to mental disorders that focus on improving the psychosocial work environment, especially reducing high psychosocial job demands, may prove effective," they wrote.

Attempts to get workers to adopt healthier lifestyles without also addressing problems in the workplace may be less effective, the study authors added.