Depression is a highly prevalent condition, affecting about 150 million people worldwide at each moment in time.
Currently, depressive disorders are the third-largest contributor to the global disease burden, and will be the disorder with the highest disease burden in high-income countries in 2030. Depressive disorders are associated with huge losses in quality of life in patients and their relatives, increased mortality rates, high levels of health service use, and with enormous economic costs.
Much of the disease burden and economic costs of depressive disorders is associated with the very high incidence of depression. About 48% of all patients with a depressive disorder in the past year indicate that they experienced the disorder for the first time in their lives, although some may have been cases of recurrent depression.
The same is true for the economic costs of depressive illnesses. About 47% of the costs of prevalent cases is associated with incident cases.
While mental health care is mainly aimed at treating depressed patients, hardly anything is done about the vast influx of new cases who develop a depressive disorder for the first time in their lives.
Prevention is also important because current treatments can reduce the disease burden of depression only to a limited extent. A modeling study in Australia estimated that about 16% of the disease burden of major depression is averted by the current health system. Because many patients do not receive an evidence-based treatment, this percentage could rise to 23% if all patients would receive evidence-based care. Furthermore, about 40% of all people with a depressive disorder do not receive any treatment. If it would be possible to deliver treatment to all patients with a depressive disorder, 34% of the disease burden of depression could be averted.
Thus, although current treatments are usually considered to be effective in treating depressive disorders, it is estimated that they can only reduce a fraction of the disease burden of depression (Andrews et al., 2004). This makes preventing new cases of depression a major priority in current evidence-based mental health care.