When a patient comes to a medical doctor with acute chest pain, the clinician usually administers a battery of tests that yield both a precise diagnosis and the assurance that appropriate treatment will be given for that specific diagnosis. However, when someone has a psychotic episode the process of determining a proper diagnosis and treatment agenda can be a bit more challenging. The majority of individuals with a psychotic disorder are diagnosed with schizophrenia or bipolar disorder. Schizophrenia is characterized by hallucinations, delusions, flat affect, and a chronic course. While bipolar can also involve hallucinations and delusions, it is principally characterized by dramatic mood fluctuations and a shifting course. Nevertheless, in the real world patients do not always fit these categorical distinctions and unfortunately there is no blood test to differentiate the two.
While psychologists are highly trained in assessment and symptomatology, in the absence of laboratory precision and biological markers, there is of course room for error in diagnosis. For instance, there is debate whether all individuals labeled schizophrenic have the same disorder, or whether psychotic disorders and symptoms are mutually exclusive or better mapped out on a continuum. These are real considerations because ultimately a precise diagnosis informs appropriate treatment.
The neuroscientist Brett Clementz and colleagues from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) are attempting to develop biologically based diagnoses for psychotic disorders. They conducted a recent study that found specific “biotypes” of psychosis that can be identified with biomarkers. The study was comprised of 711 participants diagnosed with schizophrenia, bipolar disorder, or schizo-affective disorder. Assessment consisted of what investigators call “a brain-based panel of cognitive tests, studies of eye movements, a test of cognitive control, and electro-encephalogram”. A brain-imaging scan was also done on each participant.
Unaware of clinical diagnoses, researchers analyzed the data with unbiased statistical methods in search for what they termed biotypes. The results indicated three distinct clusters of biotypes. Interestingly, these three biotypes had little relation to the three diagnostic categories involved in the study. Participants with different psychotic disorders were scattered across the three biotypes, and biotypes were not grouped simply by symptoms or symptom severity.
Although this does not mean that biotypes are more accurate or valid than the tried-and-true clinical diagnosis, this research is novel for many reasons. First, similar biotypes were also found in first-degree family members of the participants, possibly indicating a genetic basis for new classification. Second, biotypes varied according to the level of social functioning; participants experiencing more severe functional impairment shared a common biotype. Third, brain imaging revealed differences in regional gray matter according to biotype. Although none of these observations proves a definitive biological basis, the findings together provide an innovative approach to the diagnosis of psychotic disorders. It will be interesting to see if other behavioral measures or precision medicine approaches can further refine and validate these results.