Gayle Forman

If the spectrum linking everyday depression to Major Depression sometimes hinders understanding of it, it also offers an opportunity for empathy. Because almost everyone, at some point, experiences feelings of sadness, of hopelessness, of emptiness, not to mention lethargy and irritability.

Things look especially bleak for common killers such as diabetes and heart disease. Those ailments clearly have a genetic component. But when scientists survey genes looking for which mutations patients have in common, they come up empty.