Is there a symptomatic distinction between the affective psychoses and schizophrenia? A machine learning approach

Dubiety exists over whether clinical symptoms of schizophrenia can be distinguished from affective psychosis, the assumption being that absence of a "point of rarity" indicates lack of nosological distinction, based on prior group-level analyses. Advanced machine learning techniques, using unsupervised (hierarchical clustering) and supervised (regularized logistic regression algorithm and nested-cross-validation) were applied to a dataset of 202 patients with functional psychosis (schizophrenia n = 120, affective psychosis, n = 82). Patients were initially assessed with the Present State Examination (PSE), and followed up 2.5 years later, when DSM III diagnoses were applied (independent of initial PSE). Based on PSE syndromes, unsupervised learning discriminated depressive (approximately unbiased probability, AUP = 0.92) and mania/psychosis (AUP = 0.94) clusters. The mania/psychosis cluster further split into two groups - a mania (AUP = 0.84) and a psychosis cluster (AUP = 0.88). Supervised machine learning classified schizophrenia or affective psychosis with 83.66% (95% CI = 77.83% to 88.48%) accuracy. Area under the ROC curve (AUROC) was 89.14%. True positive rate for schizophrenia was 88.24% (95%CI = 81.05-93.42%) and affective psychosis 77.11% (95%CI = 66.58-85.62). Classification accuracy and AUROC remained high when PSE syndromes corresponding to affective symptoms (those that corresponded to the depressive and mania clusters) were removed. PSE syndromes, based on clinical symptoms, therefore discriminated between schizophrenia and affective psychosis, suggesting validity to these diagnostic constructs.

The effects of intravenous diazepam and hyoscine upon recognition memory

Diazepam and hyoscine are known to have amnesic effects when administered intravenously. Nevertheless, they achieve these effects by entirely different neurochemical mechanisms, and so the question arises whether they can be differentiated in terms of their effects upon different categories of encoding operations. Sixteen normal volunteers received intravenous administrations of diazepam, hyoscine, and saline following a double-blind procedure. Both drugs completely eliminated the subjects' ability to discriminate between successive lists of words in a test of recognition memory. Moreover, both drugs also impaired the subjects' ability to reject homophones or synonyms of presented words. Thus, both diazepam and hyoscine appeared to impair the use of list tags, phonemic coding, and semantic coding in storing individual stimulus items in long-term memory.