You can now buy a commercial genetic test that claims to assess your risk of developing bipolar disorder. Genetic tests for major depression and schizophrenia are also expected to reach the market soon. However, although the suspects are numerous, the genes responsible for most brain disorders remain unknown. So, when it comes to commercial genetic tests, we just don’t know enough to make the tests useful, reports the May issue of the Harvard Mental Health Letter.

One problem is that the genetics field is advancing so rapidly that it’s hard to keep up with developments, never mind figure out which ones are clinically relevant. Most experts also believe that psychiatric disorders develop because of the interplay between multiple genes, each exerting small effects. That makes finding the responsible genes harder. Further complicating matters, research has revealed that many healthy relatives of people with psychiatric disorders have risk genes. Whether a person develops an illness depends on unknown ways the risk genes interact with other genes and environmental factors.

Scientists have identified perhaps thousands of candidate genes that may contribute to psychiatric conditions. But experts continue to debate which genes are actually involved. Most candidate genes fail to hold up — meaning that the association between the gene and a given illness disappears when scientists try to replicate the results. One analysis estimated that 70% to 80% of candidate genes are false positives.

Dr. Michael Miller, editor in chief of the Harvard Mental Health Letter,notes that someday it may be possible to reliably assess risk for psychiatric disorders. But at this point, the technology—and the science — is still evolving.