Twin studies

Unfortunately, twin studies were not concordant in lending support to this result [4]. 

I The occurrence of MDD shows a familial pattern because first-degree relatives of MDD patients are about three times more likely to develop MDD compared with first-degree relatives of normal control individuals. Adoption studies and twin studies reveal that the familial aggregation of MDD is due to genetic influences.5... 

Results of family and twin studies suggest a genetic basis for bipolar disorder.4 The lifetime risk of bipolar disorder in relatives of a bipolar patient is 40% to 70% for a monozygotic twin and 5% to 10% for another first-degree relative. 

Kendler, K., Neale, M., Kessler, R. and Heath, A., Generalized Anxiety disorder in women A population based twin study. Archives of General Psychiatry 49(4), 267-272, 1992. 

Kalow, W., Tang, B. K. Endrenyi, L. (1998). Hypothesis comparisons of inter- and intraindividual variations can substitute for twin studies in drug research. Pharmacogenetics, 8, 283-9. 

Mendlewicz, J., Verbanck, P., Linkowski, P. Wilmotte, J. (1978). Lithium accumulation in erythrocytes of manic-depressive patients an in vivo twin study. Br. J. Psychiatry, 133,436-44. 

O Connor S, Sorbel J, Morzorati S, Li T-K, Christian JC. A twin study of genetic influences on the acute adaptation of the EEG to alcohol. Alcohol Clin Exp Res 1999 23 494-501. 

B17. Boomsma, D. I., Kaptein, A., Kempen, H. J. M., Gevers Leuven, J. A., and Princen, H. M. G., Lipoprotein(a) Relation to other risk factors and genetic heritability. Results from a Dutch parent-twin study. Atherosclerosis (Shannon, Irel.) 99, 23-33 (1993). 

One of the important questions with respect to mental disease (particularly schizophrenia) is whether or not it has genetic origins. The twin studies made by Kallmann20 indicate that it has. Doubtless the inheritance of susceptibility is complicated because there are probably a number of factors involved, each inherited separately and perhaps counteracting each other. The facts of biochemical genetics... 

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