From “Twin Study Reveals Epigenetic Alterations of Psychiatric Disorders” (ScienceDaily, Sep. 23, 2011), we learn:
Previous quantitative genetic analyses of schizophrenia and bipolar disorder reveal strong inherited components to both. However, although heritability for schizophrenia and bipolar disorder is estimated at 70%, disease concordance between twin-pairs is far from 100%, indicating that non-genetic factors play an important role in the onset of the diseases.
Essentially, schizophrenia and bipolar disorder are thought to have a strong genetic component, which focuses researchers’ attention on the many cases where one twin has such a disorder and the other does not. The current study looked at 22 such pairs of twins.
“Epigenetic mechanisms are linked to heritable, but reversible, changes in gene expression without a change in the underlying DNA sequence.” That’s what makes them such an attractive hypothesis for accounting for cases where genes clearly don’t rule, but something has a hand in all the same.
In this situation,
Whilst the researchers found no alterations in overall DNA methylation content between affected and unaffected twins, there were considerable disease-associated differences between twins at specific sites across the genome. The findings confirmed previously known sites implicated in psychiatric disorders as well as revealing previously unknown ones.
Finds like this help researchers design better drugs.
Years ago, researchers were locked in a hopeless “gene vs.scene” war, with one side shouting that it’s “in the genes,” and that’s just how the universe breaks out (is it?) and the other shouting it’s “society and the environment” – which meant that either the parents were to blame or else any social group the researcher didn’t like (“Oh, you mean because that family goes to church?” … ).