So CD4 counts appear to be a useful tool in assessing risk, but other factors also contribute such as lung architecture. In a retrospective study of 74 patients with interstitial lung disease on corticosteroids, 7 patients developed PCP. The mean dose at time of diagnosis was prednisone 37mg with mean duration of 10 weeks. CD4 counts ranged from 59 to 836, with a mean of 370 . The authors argued that due to their underlying lung disease, the patients were at higher risk for PCP and became infected at higher CD4 counts than patients with other underlying diseases.
PCP has also been shown to cause schizophrenia-like changes in N -acetylaspartate and N -acetylaspartylglutamate levels in the rat brain, which are detectable both in living rats and upon necropsy examination of brain tissue.  It also induces symptoms in humans that mimic schizophrenia.  PCP not only produced symptoms similar to schizophrenia, it also yielded electroencephalogram changes in the thalamocortical pathway (increased delta decreased alpha) and in the hippocampus (increase theta bursts) that were similar to those in schizophrenia.  PCP induced augmentation of dopamine release may link the NMDA and DA hypothesis of schizophrenia.