Twin concordance for DSM-III-R schizophrenia.
Level 4 - case-series / case-control
Proband-based classical twin study (observational case-control design).
PubMed 1853734 · doi:10.1111/j.1600-0447.1991.tb05563.x
What was done
Concordance rates for DSM-III-R schizophrenia and spectrum disorders were assessed in 31 monozygotic (MZ) and 28 dizygotic (DZ) schizophrenic probands and their co-twins. All participants were personally evaluated via structured diagnostic interviews.
What was found
Concordance for DSM-III-R schizophrenia was 48% for MZ twins and 4% for DZ twins. Three MZ co-twins had a non-affective psychotic disorder. Schizotypal and paranoid personality disorders occurred in both MZ and DZ co-twins without confirming a genetic relationship for Axis II disorders. A substantial number of MZ co-twins had no mental disorder.
Why it matters
The findings confirm a strong genetic component for DSM-III-R schizophrenia and related Axis I psychotic disorders, while also highlighting the presence of non-genetic factors given that over half of MZ co-twins did not develop schizophrenia.
Limits
The sample size is small (59 total pairs). The abstract does not provide confidence intervals, exact numbers for unaffected co-twins or personality disorder prevalence, nor details on zygosity determination methods or participant demographics.
Cited by
- supports If one identical twin has schizophrenia, there is approximately a 50% chance that the other twin will also develop it, compared to a general population base rate of 1%.