Selected abbreviations and acronyms BPD borderline personality disorder COMT catecholamine O-methyltransferase CPT Continuous Performance Task FDG-PET fluorodeoxyglucose positron emission tomography 5-HT 5-hydroxytryptamine (serotonin) HVA homovanillic acid PSAP Point Subtraction Aggression Paradigm SPD schizotypal personality disorder
The concept of endophenotypes in psychiatric disorders has been those developed Inhibitors,research,lifescience,medical over the last few decades. In their 1967 paper on the genetics of schizophrenia, Gottesman and Shields1 used the term endophenotype to define an illness-related characteristic, observable through biochemical testing or microscopic

examination. It is assumed that a valid and useful endophenotype is more closely related to one or more Inhibitors,research,lifescience,medical pathophysiological genes for the nosological category, compared with the entire spectrum of disorders included in the nosological category. The utility of endophenotypes in psychiatric research is now more appreciated because we have a more accurate understanding of the genetic complexity of operationally defined disorders in our current Inhibitors,research,lifescience,medical psychiatric nosology. Endophenotypes should be valid approaches to creating more homogeneous subtypes of current diagnostic categories. If endophenotypes can create more homogeneous subgroups of the traditional nosology of schizophrenia and affective

disorders, then more rapid advances in understanding these disorders at the genetic, molecular level can be made. Improved Inhibitors,research,lifescience,medical pharmacotherapy would surely follow. Criteria for an andophenotype The criteria for an endophenotype have been derived from those proposed by Gershon and Goldin2: The endophenotype should be a stable, state-independent characteristic (that is, it must be observable despite the fact that the patient may be in not partial or complete remission). The endophenotype Inhibitors,research,lifescience,medical should be heritable. The endophenotype should segregate with illness within families. Among kindreds in which the proband has the endophenotype, the endophenotype should be observable at a higher

rate among unaffected family members compared with the general population. In what follows below, we consider aspects of endophenotypes. Diagnostic specificity for an endophenotype The first criterion for an endophenotype is typically proven by demonstrating Cilengitide that the endophenotype is more common among unrelated people with a given nosological diagnosis compared with the general population. A related issue is diagnostic specificity. Should a single endophenotype be specific to a given nosological classification, such as schizophrenia or bipolar disorder? While such a one-to-one correspondence might make for easier comprehension of results, our current nosological system, distinguishing schizophrenia and bipolar disorders, is constructed on the basis of symptom clusters and – to a lesser extent – the course of illness. The extent to which our current nosological classification system reflects biological distinctions is an unresolved matter.