The Cost of Mental Illness

Over 40% of all absenteeism is due to mental illness (and most of this mental illness is unconnected with the atmosphere at work). If mentally ill people were no more absent than other workers, hours worked would rise by 1.2% in continental Europe and slightly more in Britain.

Layard, Richard; Clark, David M.. Thrive: The Power of Evidence-Based Psychological Therapies (p. 82). Penguin Books Ltd. Kindle Edition.