Re. heredity v. the environment. It is not an either or issue. Both interact dynamically to produce the result or condition.
“Hinshaw: The crucial concept here is one of “gene by environment interaction.” This means that neither genes alone, nor environments and settings alone, predict high rates of mental disorders like depression. But the risk goes way up when a person with a certain form of a particular gene has certain negative life experiences.”
“You can say it two ways: Genes matter when certain life experiences occur; or life experiences make a difference primarily for the sub-population with high genetic risk factors.”
“Finally, even for traits or conditions with a strong genetic risk, the overall levels can rise or fall through the environment alone. Height is under strong genetic control, but we’re all taller, on average, than our grandparents. This is explainable by changes in diet, not gene mutations in a couple of generations.”
