If you have a UTI, there are two ways to proceed: prescribe an antibiotic and see if it works or wait a bit for the culture and learn what AB will work because it depends upon the strain of the bacteria. Learning what genes predispose one to weight gain from AP's would work in the same way the culture test works now. One of the biggest problems with psychiatry is the amount of guesswork that prescribing currently entails. Any development that reduces the guesswork will be welcome. It wil not lead to the perfect drug as such will never exist due to differences in people's genetic and other makeup, but it will lead to a significant improvement over the status quo.