The classifications of mood disorders are many and varied, the terms, clinical, endogenous, exogenous (which can be equally as bad for the individual and as affecting and long lasting) are descriptive and not actual medical classifications, depression may also be accompanied by an anxiety disorder or as pointed out psychotic illness (e.g., bi-polar.
Here’s the actual coding our doctors use (and for general health)
http://www.who.int/classifications/apps/icd/icd10online/
To answer Bonj's questions about a 'simple' test for depression, as already noted it's very expensive and probably inaccurate at this time in our knowledge, we would routinely need to know base levels (which themselves can fluctuate daily) - crucially there is the subtle but high effect of other factors for example - social (relationships, finance, housing)
Another factor which determines our response to depression is the (bio-psychosocial) biological, psychological (which entails thoughts, emotions, and behaviours), and social factors (abbreviated "BPS") all play a significant role in human functioning in the context of disease or illness.
In a philosophical sense, the bio psychosocial model states that the workings of the body can affect the mind, and the workings of the mind can affect the body. This means both a direct interaction between mind and body as well as indirect effects through intermediate factors.
The bio psychosocial model presumes that it is important to handle the three together as a growing body of empirical literature suggests that patient perceptions of health and threat of disease, as well as barriers in a patient's social or cultural environment, appear to influence the likelihood that a patient will engage in health-promoting or treatment behaviours, such as medication taking, proper diet, and engaging in physical activity.