The media's view tends to be harsh, exploiting the ostensible absence of diagnostic biomarkers in psychiatry to cast unfair aspersions on the scientific validity of DSM-5 and its diagnostic guidelines. (1) They seem to believe that lab tests for mental illness will never be feasible. Clearly, they have not done their homework.
Consider schizophrenia. It would come as a surprise to most people inside or outside the psychiatric community that 365 biomarkers for schizophrenia have been discovered, 273 of which are identifiable in plasma. (2) Of these, 81 are diagnostic, 77 are markers of drug response, and 115 are for both. Some of these tests have been replicated at least 5 times (brain-derived neurotrophic factor, S100B, prolactin, interleukin (IL) 6, IL2, 1N5, leptin, IL 1 receptor antagonist, IL8, and IL2 receptor [alpha]). The biologic functions of these 273 biomarkers include inflammatory disease or response, respiratory disease, cellular movement, lipid metabolism, molecular transport, immunologic disease, hematologic disease, renal and urologic disease, cell-to-cell signaling, cellular growth and proliferation, cardiovascular disease, genetic disorders, psychological disorders, metabolic disease, small molecule biochemistry, molecular transport, nutritional disease, endocrine system disorders, cell death, tissue morphology, organismal survival, lymphoid tissue structure and development, antigen presentation, tissue development, carbohydrate metabolism, organ morphology, embryonic development, behavior, and digestive system development and functions. (2) Obviously, schizophrenia biomarkers overlap with multiple tissues and key biochemical and cellular processes in brain and body.
So why do none of these 213 blood tests appear in DSM-5, which had aspired to include objective methods in psychiatric diagnosis? The answer: heterogeneity Schizophrenia and other major psychiatric illnesses are not 1 disorder but syndromes comprised of numerous clinically similar but biologically different disorders. There is extensive variability among the "schizophrenias" in genetic and nongenetic etiological factors and significant heterogeneity in neurobiology, treatment response, and clinical and functional outcomes. None of the individual 273 biomarkers alone can serve as a diagnostic tool for the schizophrenias because there will be high rates of false positives and false negatives. A lab test for a syndrome is impossible!
One company recently attempted to develop a blood test for schizophrenia. (3) It used 51 biomarkers to comprise that test because none of them alone is a viable test (see this article at CurrentPsychiatrycom for a list of these 51 biomarkers). The totality of the 51 bio-markers significantly increases the likelihood of diagnostic utility but still will be short of 100% specificity.
What is the point of identifying 273 blood tests if they have not been used to diagnose a heterogeneous syndrome? I believe there are many potentially useful applications for these biomarkers:
* To identify biologic subtypes of schizophrenia
* To shed light on the multiple pathophysiologies of schizophrenia, which may provide valuable dues for new treatments
* To help identify and characterize stages of schizophrenia. …