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:Conversely, depression and dysphoria are
associated with a reduced ability to form vivid mental images of positive future events and reduced accessibility of such images (MacLeod and Byrne, 1996; Stöber, 2000; Holmes et al., 2008b; Morina et al., 2011; Holmes et al., 2016).
Category: