Often a patient with cancer receives sympathy and gets a heartfelt response from others,but victims of depression do not receive the same sympathy and instead people try to talk them out of it.
This is not me saying that people don’t get depressed, sad, troubled, anxious, nervous or even act psychotic. They do, and this is well established by common people also, but even so the question asked by you that “Is depression real?" has been raised several times, and doctors often wonder why. The real reason for this stigma is that there is no real medical test to prove depression. But this does not mean it is not real.
With the help of psychiatrists,W.H.O lays out the devastating fact that 350 million people worldwide suffer from depression. Evidence from neuroscience, genetics, and clinical investigation demonstrate that depression is a disorder of the brain. Modern brain imaging technologies are revealing that in depression, neural circuits responsible for the regulation of moods, thinking, sleep, appetite, and behavior fail to function properly, and that critical neurotransmitters -- chemicals used by nerve cells to communicate -- are perhaps out of balance. Genetics research indicates that vulnerability to depression results from the influence of multiple genes acting together with environmental factors. Studies of brain chemistry and of mechanisms of action of antidepressant medications continue to inform the development of new and better medical and psychotherapy treatments. Unlike sadness, depression does not go away with time, it does require both pharmacological and psycho-therapeutical interventions.
As quoted by a depressed individual "It's impossible to truly remember depression unless and until you're in it.” As we can see here, depression is a severely debilitating disease which can be dealt with empathy mainly.
Hence both research and clinicians have proven that depression is indeed a medical condition which currently comes under affective disorders of mental illness.