Byron Kathleen Mitchell (née Reid), better known as Byron Katie, born December 6, 1942,
is an American speaker and author who teaches a method of self-inquiry known as "The Work of Byron Katie" or simply as "The Work."
Byron Kathleen Reid (or "Katie," as she is often called) became severely depressed

Clinical depression

Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

 in her early thirties. She was a businesswoman and mother who lived in a small town in the high desert of southern California.