Fini Schulsinger

We examined the contributions of genetic factors and the family environment to human fatness in a sample of 540 adult Danish adoptees who were selected from a population of 3580 and divided into four weight classes: thin, median weight, overweight, and obese. There was a strong relation between the weight class of the adoptees and the body-mass index of their biologic parents - for the mothers, P less than 0.0001; for the fathers, P less than 0.02. There was no relation between the weight class of the adoptees and the body-mass index of their adoptive parents. Cumulative distributions of the body-mass index of parents showed similar results; there was a strong relation between the body-mass index of biologic parents and adoptee weight class and no relation between the index of adoptive parents and adoptee weight class. Furthermore, the relation between biologic parents and adoptees was not confined to the obesity weight class, but was present across the whole range of body fatness - from very thin to very fat. We conclude that genetic influences have an important role in determining human fatness in adults, whereas the family environment alone has no apparent effect.

In this study, adopted-away children of schizophrenics were compared with 67 controls—adoptees whose parents had no known psychiatric history. The rate of diagnoses in the "schizophrenia spectrum" was 31.6 percent for the entire index group, compared to 17.8 percent for the control group. The authors believe that evidence from this study supports the theory that heredity plays a significant role in the etiology of schizophrenia spectrum disorders.