Depression is a disease like any other disease; created from that old nature/nurture cocktail. To say all comedians have it is as ridiculous as saying all weather girls get diabetes. Your insides don’t know what your outside does for a living.
I had to be very patient, because there were always very nice prop guys telling me how to work the Tardis, and I was like: ‘I know how to work the Tardis! I’ve known for a very long time how to work the Tardis. Probably longer than you. So you don’t need to tell me!’