"Confirmation bias" is a term used to describe the tendency for people to favor information that confirms their preconceptions regardless of whether the information is true.
As a result, people may gather evidence and recall information from memory selectively, and interpret it in a biased way.
A recent paper ("Confirmation bias: why psychiatrists stick to wrong preliminary diagnoses", published 5/20/11 in Cambridge Journals Online) studied this phenomenon to find out whether psychiatrists and medical students are prone to confirmation bias, and whether this leads to poor diagnostic accuracy in psychiatry.
The results were revealing. After having made a preliminary diagnosis, it was common for the study participants to stick to this diagnosis, right or wrong, when presented with new information that could potentially change the diagnosis. Participants making a wrong diagnosis also prescribed different treatment options compared with participants choosing the correct diagnosis.
The paper concludes, "Confirmatory information search harbors the risk of wrong diagnostic decisions."
Now, couple this built-in bias with a blatantly fraudulent psychiatric diagnostic manual, and we get diagnostic mayhem and treatment nightmares.
The DSM IV (The Diagnostic and Statistical Manual of Mental Disorders, volume 4) is the current version of the psychiatrist's billing bible from which they must draw their diagnoses in order to collect insurance payments.
Using the DSM, a psychiatrist labels the patient with a "mental disorder", prescribes him a drug, and bills the patient's insurance. The psychiatrist with the DSM in hand can try various labels on the patient until he finds one that either fits the patient's symptoms or comes close enough to allow him to bill the patient's insurance.
As the diagnoses completely lack scientific criteria, anyone can be labeled mentally ill, and subjected to dangerous and life threatening "treatments" based solely on opinion.
Fraudulent diagnoses, harmful treatments, confirmation bias, and bogus labels = psychiatry's own psychosis, labeling everything a mental illness.