I participate most weeks during the United States school year in a "journal club" about human behavior genetics. The meetings include researchers who research genetic influences on depression and other mental disorders. It has been known for a LONG time that depression runs in families in a way that demonstrates genetic influence on depression. (In other words, adoption studies and twin studies, and especially studies on the rare monozygotic twins who are brought in separate households, make clear that genetic similarity of human individuals is linked to their similarity in risk for depression.) It has also been known for a LONG time that environmental influences, including the vague set of influences called "stress," matter for development of depression, so sometimes monozygotic ("identical") twins are discordant for depression, because they have different life experiences.
What the press release is about, and what scientists have been trying to figure out during my adult life, is what the nature of genetic influences on depression might be. It has also been known for the better of a decade, and suspected much earlier by the more astute researchers on human behavior genetics, that MANY genes influence any one human behavior trait of interest. Depression is SURELY, as we can now say by the results of massive genome-wide association studies (GWASs), influenced by hundreds of genes, each of which has only a small effect on risk. So the press release reports that an early finding that was expected to show that one gene variant had a lot to do with developing depressing has rather shown that that gene variant, as is true of all other gene variants, sometimes has no detectable effect on a patient's having depression or not.
The human mood regulation system is just that, a SYSTEM, so perturbations of many different aspects of the system can cause clinical signs that are identified as "depression." What helps depression, in general, is a both-and approach of prescribed medicine under the supervision of a physician and talk therapy provided by a psychotherapist. Most patients these days with diagnosed depressed do MUCH better than patients did a generation ago. Some patients are helped a lot by one or another of the selective serotonin reuptake inhibitors (SSRIs), and some are not helped by those medicines at all. And that's all because depression is a clinical condition with a diverse set of underlying biochemical causes, as we know for sure from GWAS studies.
Further study of genetic relationships to depression should help develop new drugs that help some patients who are not helped by current drugs or that help patients who are already helped by existing drugs but with fewer side effects. But we are NOWHERE near being able to use genetic test results to decide which drug to use first: patients have to talk to their doctors about how they are feeling as they undergo treatment. Your best bet for finding good treatment if you feel depressed is to find out what has helped a NEAR relative who has also suffered depression.