Thanks to Furious Seasons for pointing me to this study suggesting what many have known a long time, namely that bi-polar disorder is overdiagnosed, though I would submit that it is but one of several instances of overdiagnosis.
"Lead author Mark Zimmerman, M.D., director of outpatient psychiatry at Rhode Island Hospital and associate professor of psychiatry and human behavior at The Warren Alpert Medical School of Brown University, notes, "Clinicians are inclined to diagnose disorders that they feel more comfortable treating. We hypothesize that the increased availability of medications that have been approved for the treatment of bipolar disorder might be influencing clinicians who are unsure whether or not a patient has bipolar disorder or borderline personality disorder to err on the side of diagnosing the disorder that is medication responsive." He continues, "This bias is reinforced by the marketing message of pharmaceutical companies to physicians, which has emphasized the literature on the delayed and underrecognition of bipolar disorder, and may be sensitizing clinicians to avoid missing the diagnosis of bipolar disorder."
That a patient might be diagnosed as bi-polar, in one setting and borderline in another while presenting the same symptoms suggests how primitive our ability to make distinctions really is. Local custom, training of the examiner, examiner biases, insurance coverage, perceived stigma carried by various diagnoses, and funding sources can all influence the diagnosis made as much as the behavior and history of the patient.
That such factors as funding sources and examiner bias influence diagnosis goes against the image of the medical model as scientific. However, subjective and external factors often matter more than the symptoms displayed. In private practice, the fact that medical and insurance records cannot be guaranteed to be private, the tendency is to choose the least stigmatizing diagnosis possible. Occasionally a psychiatrist or therapist might apply a more serious diagnosis to someone they find irritating, in an unconscious attempt at retaliation. Or a facility has beds for patients with one kind of diagnosis but not another, so the effort is made to fit the patient where the space is. Or health insurance severely limits coverage for treatment for minor disorders but is more generous for ones that are more serious, resulting in the push to gain coverage, not strive for accuracy in diagnosis. All of these disturbances, in what we might like to believe are an orderly and scientifically based process, reflect variations in the consensus reality and its deviance from the ideal.
Another factor is the mostly unconscious desire of the prescriber to be perceived by the patient as helpful. Peter Giovacchini wrote some years ago that he thought the reason there were so many antidepressants on the market was that the depressed often do not respond rapidly to therapy and thus can be less than gratifying to treat but when the psychiatrist could prescribe a medication, the patient was often very grateful. Of course he was writing in the day when most psychiatrists did therapy as well as prescribe medications.
More than sixty years ago, Jung was expressing doubts about the value of establishing a diagnosis:
It is generally assumed in medical circles that the examination of a patient should lead to the diagnosis of his illness, so far as this is possible at all, and that with the establishment of the diagnosis an important decision has been arrived at as regards prognosis and therapy. Psychotherapy forms a startling exception to this rule: the diagnosis is a highly irrelevant affair since, apart from affixing a more or less lucky label to a neurotic condition, nothing is gained by it, least of all as regards prognosis and therapy. (Jung, Collected Works, vol. 16, p86)