Molecular abnormalities in the major psychiatric illnesses: Classification and Regression Tree (CRT) analysis of post-mortem prefrontal markers

Post-mortem specimens from the Stanley Foundation Neuropathology Consortium, which contains matched samples from patients with schizophrenia, bipolar disorder, non-psychotic depression and normal controls (n = 15 per group), have been distributed to many research groups around the world. This paper provides a summary of abnormal markers found in prefrontal cortical areas from this collection between 1997 and 2001. With parametric analyses of variance of 102 separate data sets, 14 markers were abnormal in at least one disease. The markers pertained to a variety of neural systems and processes including neuronal plasticity, neurotransmission, signal transduction, inhibitory interneuron function and glial cells. The data sets were also examined using the non-parametric Classification and Regression Tree (CRT) technique for the four diagnostic groups and in pair-wise combinations. In contrast to the results obtained with analyses of variance, the CRT method identified a smaller set of nine markers that contributed maximally to the diagnostic classifications. Three of the nine markers observed with CRT overlapped with the ANOVA results. Six of the nine markers observed with the CRT technique pertained to aspects of glutamatergic, GABA-ergic, and dopaminergic neurotransmission.