https://news.ycombinator.com/item?id=33624032> (8) Family genetic studies. The phrase “family genetic studies” is commonly used in psychiatry to refer to designs in which investigators examine the familial aggregation of one or more disorders, such as panic disorder or major depression, within intact (i.e., non-adoptive) families (e.g., Weissman, 1993). Given that the familial aggregation of one or more disorders within intact families could be due to shared environment rather than—or in addition to—shared genes (Smoller and Finn, 2003), the phrase “family genetic study” is misleading. This term implies erroneously that familial clustering of a disorder is necessarily more likely to be genetic than environmental. It may also imply incorrectly (Kendler and Neale, 2009) that studies of intact families permit investigators to disentangle the effects of shared genes from shared environment. Twin or adoption studies are necessary to accomplish this goal.
> (9) Genetically determined Few if any psychological capacities are genetically “determined”; at most, they are genetically influenced. Even schizophrenia, which is among the most heritable of all mental disorders, appears to have a heritability of between 70 and 90% as estimated by twin designs (Mulle, 2012), leaving room for still undetermined environmental influences. Moreover, data strongly suggest that schizophrenia and most other major mental disorders are highly polygenic. In addition, the heritability of most adult personality traits, such as neuroticism and extraversion, appears to be between 30 and 60% (Kandler, 2012). This finding again points to a potent role for environmental influences.