Depression is associated with significant loss of quality of life, increased morbidity and mortality and enormous economic burden, the largest component of which derives from lost work productivity. Global Burden of Disease analysis shows that unipolar depressive disorders are ranked as the fourth leading cause of burden among all diseases. By 2020, the burden of depression is expected to increase to 5.7% of the total burden of disease, becoming the second leading cause of global disability-adjusted life years lost. Functioning is increasingly taken into account for the diagnoses of depression as well as for evaluating the effectiveness of treatments. The American Psychiatric Association included the concept of functioning as diagnostic option for assessing major depressive disorder in the 4th edition of its Diagnostic and Statistical Manual of Mental Disorders.

Functioning is increasingly being taken into account when assessing the impact of bipolar disorder (BD) on the individual as well as on the effectiveness of treatment. However, the studies published on the measures assessing functioning, disability, and/or quality of life in relation to BD show little standardization in the use of these instruments. In addition, these instruments typically cover only selected aspects of the entire experience associated with BD; it is also important to note that no BD-specific instruments exists to date. It would, therefore, be valuable for clinical practice and research to have a practical tool that covers the typical spectrum of problems in functioning of individuals with BD. The project "Developing the ICF Core Sets for BD " begun in the summer of 2007 as a collaboration between the ICF Research Branch, the Autónoma University of Madrid, the World Health Organisation (WHO), the Bipolar Disorder Programme at the Institute of Neurosciences at the Barcelona University Hospital Clinic, the European Bipolar Research Network and the International Society for Bipolar Disorders (ISBD) and the International Society of Physical Medicine and Rehabilitation (ISPRM).