Patricia Houston's Theory on What Killed Whitney Houston

"Oprah's Next Chapter" host Oprah Winfrey sat down with Whitney Houston's daughter, Bobbi Kristina; brother, Gary Houston; and sister-in-law, Patricia Houston, for an exclusive interview.

In this sneak preview, Patricia revealed her concern for Whitney's lifestyle, and whether she thought drugs would someday claim Whitney's life.

Watch the special episode of "Oprah's Next Chapter," Sunday, March 11 at 9:00 PM on OWN.