This 12 week randomized placebo-controlled study will compare the effects of 10 mg and 20 mg
of a mixed amphetamine salt, extended release medication (trade name Adderall XR) to placebo
on objective measures of processing speed and memory, as well as on self-reported measures of
cognition and quality of life. To be enrolled in the study, MS subjects must demonstrate
impaired processing speed on the Symbol Digit Modalities Test (SDMT).