Lifetime rates of affective disorder in co-twins of bipolar twin probands
| Ref No | Sample | Lifetime rates of affective illness in co-twin of bipolar twin probands (probandwise concordance rate) | Comment | ||||
|---|---|---|---|---|---|---|---|
| 41 | Norway twin and psychosis register. 6 MZ pairs with BP proband | BP-BP: | MZ: 67% | Small sample and no operationalised diagnostic criteria | |||
| 42 | USA Veteran twin register. 5 MZ, 15 DZ pairs (out of 15 909 twin pairs on register) | BP-BP: | MZ: 20% | Inferior methodology. Note the very low rate of BP disorder detected in the twin sample (0.07%) | |||
| DZ: 0% | |||||||
| 43 | Denmark twin and psychiatry registers. 34 MZ, 37 DZ pairs | BP-BP: | MZ: 62% | Despite lack of operationalised diagnostic criteria this is a detailed study and is the best available | |||
| DZ: 8% | |||||||
| BP-BP/UP: | MZ: 79% | ||||||
| DZ: 19% | |||||||
| 44 | Norway twin register. 4 MZ, 6 DZ pairs | BP-BP: | MZ: 75% | Small sample which may overlap partly with that of ref 41 | |||
| DZ: 0% | |||||||
| BP-BP/UP: | MZ: 100% | ||||||
| DZ: 0% | |||||||
| 45 | Sweden twin and psychiatric registers. 13 MZ, 22 DZ pairs | BP-BP: | MZ: 39% | This has the strength of being a large epidemiological twin sample but the weakness of using questionnaire assessments. Likely to underestimate concordance | |||
| DZ: 5% | |||||||
| BP-BP/UP: | MZ: 62% | ||||||
| DZ: 14% | |||||||
| 46 | UK psychiatric hospital twin register. 22 MZ, 27 DZ pairs | BP-BP: | MZ: 36% | Diagnoses based on hospital notes. Likely to underestimate concordance | |||
| DZ: 7% | |||||||
MZ: monozygotic; DZ: dizygotic. Sample size refers to number of twin pairs in which at least one twin suffered with bipolar disorder. BP-BP refers to twin pairs in which both have narrowly defined bipolar disorder. BP-BP/UP refers to twin pairs in which one has bipolar disorder and the other has broadly defined bipolar phenotype (including unipolar depression).