Boy, am I relieved. Turns out there’s a credible explanation for those frequent dark nights of the super-ego:

There have been more than 20 studies that suggest an increased rate of bipolar and depressive illnesses in highly creative people, says Kay Redfield Jamison, professor of psychiatry at Johns Hopkins University and author of the “An Unquiet Mind,” a memoir of living with bipolar disorder.

Experts say mental illness does not necessarily cause creativity, nor does creativity necessarily contribute to mental illness, but a certain ruminating personality type may contribute to both mental health issues and art.

“Unquestionably, I think a major link is to the underlying temperaments of both bipolar illness and depression, of reflectiveness and so forth,” Jamison said.

It’s good to know why—especially after reading Roy Clark’s essay about David Foster Wallace—I can’t get to sleep before 2 a.m. most nights, and why I write best when I’m absolutely miserable.

(Roy: just because you don’t believe in “tortured artist” syndrome doesn’t mean it ain’t real. Put that one in your column and smoke it!)