Table 3

Within-pair Spearman correlations of symptom dimensions in concordant twin pairs

Dimension RDC schizophrenia All RDC psychoses
MZ MZ DZ
n ρ n ρ n ρ
RDC, Research Diagnostic Criteria; MZ, monozygotic; DZ, dizygotic; n, number of twin pairs counted pairwise; ρ, Spearman correlation coefficient; FA1, first factor analysis; FA2, second factor analysis.
1. Of the 26 MZ twins from pairs concordant for schizophrenia, 25 had the maximum score of 2.
2. There were too few concordant DZ pairs from FA1 for analysis (n=9).
*P < 0.05; ** P < 0.005; *** P < 0.0005.
Symptom scores
Positive 13 - 44 0.19 13 0.27
Negative 13 -0.01 44 0.27 13 -0.03
Disorganised 13 0.05 44 0.63*** 13 0.24
Manic 13 -0.35 44 0.42* 13 -0.07
Depressive 13 0.02 44 0.21 13 -0.12
General psychotic 13 0.16 44 0.47** 13 0.27
Factor scores (FA1)
First-rank delusions 13 -0.29 43 -0.11 9 -
First-rank hallucinations 13 0.14 43 0.10 9 -
Paranoid 13 -0.03 43 0.24 9 -
Other hallucinations 13 0.20 43 0.05 9 -
Negative 13 0.46 43 0.59*** 9 -
Disorganised 13 0.64* 43 0.42* 9 -
Factor scores (FA2)
Manic 13 -0.46 43 0.44** 11 -0.19
Depressive 13 -0.23 43 0.21 11 0.26
General psychotic 13 0.04 43 0.53*** 11 0.17