BPI-SF interference score asks about the degree to which pain interferes with mood, walking and other physical activity, work, social activity, relations with others, and sleep. BPI-SF interference score ranges from 0 (no interference) to 10 (interferes completely). Response is defined as a >=50% reduction in the Maier subscale score from baseline. The Maier subscale (Items 1,2,7,8,9,10) represents "core" symptoms of depression. Total subscale scores range from 0 (normal) to 24 (severe). Factors used for adjustment for least squares means are listed in 'Other relevant information' section.