Are there valid subtypes of schizophrenia? A grade of membership analysis.
OBJECTIVE
Cluster analysis has had limited success in establishing whether there are subtypes of schizophrenia. Grade of membership (GoM) analysis is a multivariate statistical technique which has advantages when, as in schizophrenia, individuals conforming to pure types are uncommon and mixed forms are frequent.


METHODS
GoM analysis was applied to 118 chronic schizophrenic patients. The patients were of all clinical subtypes, including 13 with simple schizophrenia. Both current and 'lifetime' symptoms were assessed, and two different rating systems were used.


RESULTS
Specifying 3 pure types resulted in robust findings across analyses. One pure type corresponded to paranoid schizophrenia, one to simple schizophrenia and the third combined elements of hebephrenic and catatonic schizophrenia. Specifying 4 pure types split the original 3 pure types in ways which were not clinically intuitive.


CONCLUSIONS
GoM analysis divides schizophrenia into subtypes along conventional lines, with the proviso that hebephrenic and catatonic schizophrenic patients are not separable, at least in the chronic stage of the illness.
Pomarol-Clotet
Edith
E
Benito Menni Complex Assistencial en Salut Mental, Barcelona, Spain. edith.pomarol @ gmail.com
Salvador
Raymond
R
Murray
Graham
G
Tandon
Subash
S
McKenna
Peter J
PJ
D000328:Adult; D000368:Aged; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011594:Psychometrics; D012559:Schizophrenia / Q000145:classification* / Q000175:diagnosis*; D012560:Schizophrenia, Catatonic / Q000145:classification / Q000175:diagnosis / Q000523:psychology; D012562:Schizophrenia, Disorganized / Q000145:classification / Q000175:diagnosis / Q000523:psychology; D012563:Schizophrenia, Paranoid / Q000145:classification / Q000175:diagnosis / Q000523:psychology; D012565:Schizophrenic Psychology; D013577:Syndrome; D055815:Young Adult