Victoria Costello, a science writer, author, and Emmy Award winning documentary maker, complains in her blog for Psychology Today about what she sees as a recent "trend (back) towards the denial of mental illness, especially the debilitating disease of depression." She takes the opposite view to those who suggest that there are too many kids on psychiatric drugs, advocating "early intervention with high risk children as soon as symptoms appear". Ms. Costello is explicit in her presumption that mental illnesses like depression are brain diseases predisposed by genetics.
But the medical and scientific fact is that there is no proven biological basis for any mental disorder. Not one single objective medical test for any mental disorder, including schizophrenia, depression, bipolar, ADHD... has been recommended for inclusion in DSM-V. Prior to discussing the various hypotheses which Ms. Costello refers to with so much hope and fervor in her blog, and prior to discussing various other hypotheses which she neglects to mention, no up-to-date textbook on psychiatry ever fails to disclaim, e.g., "The biological basis of schizophrenia remains unknown."
This is not someone's opinion, it's the actual state of medical/biological science. What is opinion is that maybe someday soon the causes of mental illnesses will be discovered to be brain or other somatic disease. But so far, no. Thus depression, no matter how much it has hurt Ms. Costello's family for three generations, is only a metaphorical disease. It is not a literal disease.
When someone "denies mental illness" in the sense that Ms. Costello says is so dangerous, they are most often just saying they don't want a particular treatment that somebody else is trying to force on them. Sometimes, they are saying that people generally should have the right to be truthfully informed about, and to refuse, for any reason or for no reason, treatments that others want to force on them. Imagine that!
I'm going to propose a new mental disorder: Prodromal Anosognosia. This is when people merely show tendencies toward possibly denying mental illness in the future. For example, anyone reading this blog more than once probably has sympathy for the idea that orthodox biological psychiatry can be legitimately criticized. This could be dangerous.
Anyone who tends toward denying mental illness should perhaps be treated to ensure that they don't develop any full-blown disbelief (anosognosia), and wind up really denying mental illness.
As a matter of fact, if you even suspect, right now, that Prodromal Anosognosia is a satirical invention, or that it could become a totalitarian political device, you're actually showing signs of the disease!