Medical-based understanding of absenteeism finds support in research that links absenteeism for medical reasons with mental and behavioral disorders, diseases of the digestive system, neoplasms, and diseases of the genitourinary system. This excludes pregnancy, childbirth, and puerperium. The cost of this, in euros, is 7.43 billion per year for men and 9.66 billion for females (6.7 billion euro after taking out pregnancy, childbirth, and puerperium.) Research shows that over one trillion dollars are lost annually due to productivity shortages as a result of medical-related absenteeism. The line between psychological and medical causation is blurry, given that there are positive links between both work stress and depression, and absenteeism. Depressive tendencies may lie behind some of the absence ascribed to poor physical health, as with adoption of a "culturally approved sick role". This places the adjective "sickness" before the word "absence", and carries a burden of more proof than is usually offered.