In the following sections, I shall endeavor to show to what extent the current diagnostic system has furthered or impeded progress. The group of mood disorders, in particular the construct of major depression, will be used as a paradigm, but the same reasoning can be applied to most of the diagnostic see more constructs currently distinguished. Problems of validity Predictive validity

is the basic quality any diagnostic construct should possess. A diagnosis, once made, should allow reliable prognostication of symptoms, cause, course, outcome, and response Inhibitors,research,lifescience,medical to treatment. This is clearly not the case as far as the diagnostic construct of major depression is concerned: The diagnosis of major depression is based on evidencing Inhibitors,research,lifescience,medical X out of a scries of Y symptoms, irrespective of which ones. This construct therefore encompasses a wide range of syndromes without providing any information on the type of depressive syndrome thus observed. Major depression can be precipitated by a variety of etiological factors, psychological, biological, or related

to living conditions. In some instances, no precipitating factors are demonstrable. With regard to pathophysiology, current hypotheses postulate a causal role of serotonergic dysfunction and hypothalamo-pituitary-adrenocortical (HPA) axis disturbances. These Inhibitors,research,lifescience,medical have indeed been found to be associated with major depression in some patients, Inhibitors,research,lifescience,medical but not in others, without these patient subgroups coinciding with any of the currently distinguished depression subtypes. Furthermore, disturbances of these systems are not specific to depression, but occur in other diagnostic categories as well.3-4 Course and outcome also fail to show a characteristic pattern.5,6 Inhibitors,research,lifescience,medical Some patients only develop a single episode, whereas the majority of them experience several. One patient may recover completely, another will suffer

from residual symptoms, and in another still chronicity will set in.7,8 Treatment response, finally, is difficult to predict. Antidepressants may achieve complete recovery, partial response, or no response at all. Psychological interventions will be helpful in some patients, or totally useless in others. The construct of major depression therefore shows great Liothyronine Sodium variability at almost every diagnostic level. Hence there is no question of any predictability being associated with the diagnostic characteristics: no single characteristic is reliably predictive of any other. In other words, the predictive validity of this construct is all but null. Not only does the construct of major depression encompass a wide range of syndromes, but in the majority of cases it is also associated with other disorders, most notably personality and anxiety disorders.10-13 Thus it appears that major depression is not so much a diagnostic entity as a diagnostic multiplicity.