Depression is increasingly starting to be seen as a neurobiological disorder as we learn more.

In my own opinion, we need to stop viewing "mental health" as a separate class of conditions from general/physical health. A mental illness is a health/medical condition just like any other and shifting our views and diagnostic criteria in that direction would do a lot to remove the stigma associated with mental illness.

Someone with depression has a chronic illness, not a temporary "it's just in your head" condition.