Here is an excerpt from a paper that I wrote regarding the criminal incompetence of the APA in its approach to diagnosing mental disorders:
"The Diagnostic Statistical Manual of Mental Disorders-IV (DSM-IV) incorporates an outline that includes an “assessment of a patient’s cultural identity… cultural explanations of the client’s illness, cultural elements of the relationship between the client and the mental health professional, cultural factors related to the psychosocial environment and levels of functioning, and the overall cultural assessment for diagnostic care” (APA, 1994, in Campinha-Bacote, pp. 40-41). However, the DSM-IV offers no guidance for the practitioner in assessing culture-bound disorders, and even cautions mental health practitioners against using DSM-IV diagnoses for non-Western patients (Marsella, 2003, in Campinha-Bacote, p. 41). For all intents and purposes, the APA caveat contained in its own diagnostic standard effectively renders the DSM-IV useless for the accurate diagnosis of disorders in the client who has a non-Western cultural background. This leaves the practitioner in a very difficult position in which he or she may be required to utilize subjective data to reach an objective, empiric diagnosis. This situation makes diagnostic clarity all the more elusive and difficult to achieve."
(Yeah, I scored a 4.0 on that paper, plus extra credit for finding that APA caveat. My Psych prof had no idea it existed until I showed it to him. It rocked his world.) Then there are the three letters "NOS." In APA parlance, it stands for "Not Otherwise Specified." What that means is that if you have a mental health problem that they can't figure out, they simply slap a diagnosis on you (that you carry for the rest of your LIFE) like "Mood Disorder," and then add "NOS."
Here's what "NOS" really means: NOS= "I don't know what the f*** I'm doing and I would have been a thoracic surgeon but was too frigging lazy to do my homework. So what if I may ruin some nutjob's life? I still make my Beamer payment."
Your points are well-taken, a bit cynical, but relevant indeed. The psuedo-sciences of psychiatry and psychology are only a bit over a century old, and during that time we have seen theories taken as fact that have later proved egregiously wrong and destroyed people’s lives. However, we’ve also seen the development of therapies and drugs that improve or save lives (sometimes without knowing exactly what the mechanism is that improves the patient).
Psychoneurobiology is more “scientfic” but even there the facts are somewhat nebulous, all the theories about brain chemistry that is the current basis of understanding disorders is not measurable directly, only inferred from physical, mental and emotional symptoms.
Even the new brain scans haven’t “proven” scenario “A” on the scan is definitely disease “A” in the DSM. As you say, diagnosis is very tricky, and probably also influenced by the doctor’s prejudices, ignorance, pressure from the patient or parents, teachers, etc.
I agree with you, much is still unknown, and unfortunately, sometimes, but not always, misconstrued or even misused.