Mental Illness: Not in Your Genes

Even before the Human Genome Project wrapped up in April 2003, scientists have worked overtime to find the gene or genes responsible for autism, schizophrenia, Alzheimer’s, ADHD, alcoholism, depression, and other ailments "known" to have major genetic components. The problem is, many neuropsychiatric ailments that are assumed to have a major genetic component don’t seem to have one.
More than a decade after the sequencing of the human genome, there is still no reliable genetic test for autism, Alzheimer’s, schizophrenia, or any other major neuropsychiatric disorder (except for Huntingon’s disease, for which there was already a test, prior to the Human Genome Project). In late 2012, scientists claimed (in a paper in Molecular Psychiatry) that a genetic test for autism had been devised. In actuality, the "test," a classifier developed using data from 237 single-nucleotide polymorphisms in 146 genes, proved unreliable. The software had been trained on one set of human genes (from central Utah) and tested against another set (from northern Europe); it correctly predicted if you were of northern European descent, not whether you might be at risk for autism.