Neurobiologisk analys av olika psykossjukdomar

Each biotype overlapped with the traditional diagnostic categories. For example, among Biotype 1 cases, 59 percent had a schizophrenia diagnosis, while among Biotype 3 cases 44 percent had a bipolar disorder with psychosis diagnosis. Among Biotype 3 cases, 32 percent had schizophrenia, and among Biotype 1 cases, 20 percent had bipolar disorder with psychosis.

Differences in brain structure also distinguish the three biotypes, further validating the categorizations. On brain MRI scans, Biotype 1 cases — and to a lesser degree Biotype 2 cases — showed reduced gray matter, the brain’s working tissue, across several areas of the cortex, or outer mantle, known to process higher-order information. By contrast, in Biotype 3 cases, the largest of the groups, such reduced gray matter was mostly localized in emotion-processing areas in deeper brain regions. No brain structural differences distinguished the traditional categories of schizophrenia and schizoaffective disorder from each other.

The different patterns of biomarkers across the biotypes may help to explain discrepancies in replicating biomarker studies across different clinical research centers, say the researchers. For example, since they tend to be the most compromised, Biotype 1 cases are more likely to be recruited in inpatient settings, while Biotype 2 and -3 cases are more likely to be found in outpatient settings. So even if patients have the same nominal diagnosis, they might tend to have different underlying illness processes. Similarly, researchers with mostly Biotype 3 cases might conclude that not much can be learned from studying first-degree relatives (their relatives were largely normal on the biomarkers) — and/or that a large portion of the genetic risk for psychosis comes from spontaneous mutations.