Neurosis is likely to be caused by upbringing and other environmental influences, but a study of identical twins who were adopted indicates schizophrenia and other major mental illnesses are genetic, rather than environmental.
That news is good and bad, according to Dr. Paul Wender, director of psychiatric research at the University of Utah Medical School. While a child may not be able to escape the hereditary predisposition to serious mental illness, "there is a cause for hope that someday we will isolate the gene that is abnormal" as research has for other diseases.Wender discussed the role of genetics in psychiatric disorders during an LDS Hospital "Grand Rounds" lecture Thursday.
One-third of the population is affected by three major families of psychiatric illnesses: biological disorders, life experiences like abuse and neglect "and how we can be bent out of shape" by them, and ordinary issues of human happiness. (If you're 5-foot-9 and dream of being a forward in the NBA, you may not be very happy, according to Wender.)
"It is a long-known fact that mental illness runs in families," he said. Shakespeare referred to it. Early scientists and doctors discussed it. But when attempts were made to document it, the results weren't always clear. "They found that with someone with schizophrenia, about 10-15 percent of the siblings had the illness. But that doesn't tell you whether it's hereditary or environmental."
In the 1800s, a doctor decided to compare identical and fraternal twins. In the latter, the degree of illness was no more closely related than in any pair of siblings. But it was difficult to collect identical twins with mental illnesses. Furthermore, identical twins are not identical in everything. One can be diabetic and the other not, for instance. Or one can have a club foot.
Wender was a member of a National Institute of Mental Health research team that studied twins in Denmark who had been adopted by non-relatives. Scandinavia is more open with adoption records.
The team found that about 10 percent - 1,500 - of the children, adopted as infants, had been hospitalized for psychiatric disorders. About 70 were identified as schizophrenic. Investigating the biological relatives they could locate, they found that one-fifth had schizophrenia or were "borderline." Adoptive relatives of both the mentally ill adopted children and those not suffering mental illness were statistically the same in mental illness occurrence. Obviously, Wender said, the illness is genetic, rather than environmental.
"The degree of neurosis is related to how deviant an upbringing is, but not schizophrenia. On the other hand, studies of felonious behavior indicate a strong environmental effect."
In case of mental illness, Wender said, he advises his students to diagnose the parents by the child and the child by the parents.
"You should choose your biological parents with exquisite care," he quipped, "because after that the jig is up."