Table 4

Logistic regression of RDC lifetime-ever psychotic diagnoses in co-twins on symptom dimensions in probands, conditional on zygosity and age of co-twins at last follow-up

Dimension Odds ratios
Schizophrenia (n=106) Schizoaffective (n=45) Mania (n=49) All psychoses (n=222)1
RDC, Research Diagnostic Criteria; FAI, first factor analysis; FA2, second factor analysis.
1.One monozygotic and one dizygotic proband did not qualify for any RDC psychotic diagnosis; and 215 probands had FAI scores (i.e. had at least one of the symptoms entered into the factor analysis).
2.The odds ratio for positive symptom scores in schizophrenia was not reported because 103/106 probands had the maximum score of two.
*P <0.05 (d.f.=1).
Symptom scores
Positive (0-2)2 1.62 1.94 1.02
Negative (0-2) 1.09 0.10 0.12 1.06
Disorganised (0-2) 1.54 0.87 2.52 1.23
Manic (0-5) 0.87 1.06 1.67 1.21*
Depressive (0-5) 1.01 1.57 1.23 0.99
General psychotic (0-6) 1.27 0.68 1.20 1.07
Factor scores (FAI)
First-rank delusions 0.66 0.83 4.49 0.82
First-rank hallucinations 0.75 1.05 1.29 0.91
Paranoid 0.94 1.33 0.33* 0.74
Other hallucinations 1.45 0.95 0.93 1.25
Negative 1.21 0.55 0.59 1.02
Disorganised 1.48 1.26 2.57 1.62*
Factor scores (FA2)
Manic 0.75 1.18 3.54 1.45*
Depressive 0.98 1.88 1.27 0.97
General psychotic 1.58 0.33 1.23 1.07