Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Adult patients with ADHD more often exhibit lower academic and professional achievement, fewer close friendships, increased traffic violations and accidents, increased absenteeism, higher frequencies of divorce, and greater job loss through early termination or resignation than do their counterparts without ADHD (Barkley, Fischer, Smallish, & Fletcher, 2006; Barkley, Guevremont, Anastopoulos, DuPaul, & Shelton, 1993; Biederman, Faraone, et al., 2006; Biederman et al., 2008; Kessler et al., 2006; Secnik, Swensen, & Lage, 2005; Sobanski, 2006).
Category: