 This study will last 12 weeks. Participants will be randomly assigned to receive either modafinil or placebo daily for 4 weeks. Participants who show an improvement in symptoms will receive modafinil for an additional 8 weeks. Participants who do not respond to modafinil will have the opportunity to receive other drug treatments. All participants will have weekly study visits for the first 4 weeks of the study and biweekly visits for the remainder of the study. At each visit, participants will complete various tasks to determine cognitive function and self-report scales will be used to determine symptoms of depression and fatigue. 