It Takes a Genome: How a Clash Between Our Genes and Modern Life Is Making Us Sick

Misbehaving Serotonin

Depression is one of the most genetic illnesses there is; yet paradoxically no one has yet found a gene for depression. Certainly not in the sense of “if you have this mutation, you will be bipolar,” but also not even conclusively in the sense of “if you have this variant, you’re strongly predisposed.” There are some suggestions, as we’re about to see, but they’re at best of the “maybe, sometimes, depends on the circumstances” type—which actually makes them interesting.

Even though bipolar disorder afflicts only a few percent of the population, identical twins have about a 70 percent concordance rate. That’s maybe a fiftyfold increase in susceptibility by sharing all your genes (and the womb and upbringing) with your twin. ...