Psychological complaints were responsible for 11 percent of sick days taken by German workers in 2008, the study by the Federal Chamber of Psychotherapists found. That is nearly double the figure from 1990.
Along with better diagnoses by doctors, the growing burden of the modern workplace was overwhelmingly responsible for the increase, said the chamber's president, Rainer Richter, in Berlin.
The risk of depression increased when workers felt they had no influence over the progress or success of their job and, at the same time, little recognition for their work in the form of pay or job security.
The worst affected were people in the service sector and in particular, people who worked in call centres. Such workers were twice as likely to skip work on mental health grounds than the workforce at large.
Women were on average twice as likely to be affected by workplace-related depression as men.
By comparison, building workers are one third to one half less likely to be absent for mental health reasons than employees in other sectors.
Treating mental illness cost Germany's health insurers about €4.3 billion in 2004.
But even more damaging for mental health is losing one's job. According to the annual health report from health insurers, the unemployed are three to four times more likely to suffer depression than people in work. In most cases, the illness was not the cause of the unemployment but rather the result of it, through reduced self-esteem.
But diagnosing mental illness is complex. The eastern states of Germany, despite having higher unemployment, have on average lower rates of diagnosed mental illness – aside from Berlin.
The lowest rate is in Saxony-Anhalt, where the proportion of sick days owing to mental illness were between 22 and 30 percent lower than the national average. This would jibe nicely with the state's motto "Land der Frühaufsteher" - or the state of early risers.
The national leaders were Hamburg and Berlin which were 50 percent and 25 percent above the national average respectively. A possible reason, Richter said, was that there were more mental health services in the cities.
Richter called on employers – particularly those in the service sector – to offer humane working conditions. Something could be learned from the industrial revolution, he said: then, workplace morale had been boosted on production lines by giving workers are greater say in how the factory floors were run.
He also urged call centre operators to think about how many conflict-fuelled conversations their workers could bear each day.