Prozac and its kin — drugs called selective serotonin reuptake inhibitors (SSRIs) — were first discovered in 1972. They address one hallmark of depression: low levels of the molecule serotonin, which neurons use to signal one another. By preventing a protein called serotonin transporter (SERT) form absorbing the serotonin back into neurons that release it, the drugs boost serotonin levels in the junctions between cells. It is exciting that the…