In addition, even if there is a real effect here, it is so small, and the interactions so complex, that it's probably useless. For example, even if this neande

In addition, even if there is a real effect here, it is so small, and the interactions so complex, that it's probably useless. For example, even if this neanderthal gene happens to causally affect depression by 1%, that pathway might be something like gene => slightly wider shoulders => that body structure is slightly more or less likely to lead to certain life outcomes, like marrying early or getting promoted or getting targeted by pickpockets => change in depression risk As a result, the gene might currently lead to a 1% increase in depression risk, but in a few years it might do the opposite, if things change in the surrounding culture and those intermediary steps behave a little differently.