Is there a " biological " disease that resembles clinical depression?
There are many biological diseases that simlulate depression (or at least have the capacity to). These genrally have to be ruled out before a diagnosis of depression can be given. not my area of expertise but things such as brain tumours or glandular disorders can simulate depressive symptoms. There are also biological diseases that can simulate other psychiatric symptoms such as psychosis etc. however all of these generally come with other symptom and most of the time have simple ways to be tested for such as MRIs or Blood tests.