Inclusion Criteria:
* MS of any type as per 2010 McDonald's criteria
* Males/females between the ages of 18-59, inclusive
* Have not received corticosteroids or experienced a relapse in the last ninety days
* An Expanded Disability Status Scale (EDSS) of ≤ 7.0
* If female, must neither be pregnant nor breast-feeding (pregnancy test to be complete at enrollment for those of childbearing potential)
* Willingness to use appropriate contraceptive measures (hormonal contraceptives (i.e., oral contraceptives, patch, vaginal ring, injectables or implants); intrauterine device or system; vasectomy or tubal ligation) both males and females at least 28 days before, for the duration of the trial and for at least 30 days after the study ends unless post-menopausal (no menses for 12 months) or surgically sterile female (complete hysterectomy, bilateral salpingectomy, or tubal ligation with documentation) or vasectomised male partner (with appropriate documentation of azoospermia).
* Ability to complete the neuropsychological tests included in the battery including binocular visual acuity of ≤ 20/70 corrected or uncorrected
* Stable medications for over the last 30 days with no planned change for the duration of the study.
Exclusion Criteria:
* Evidence of other medical potential cause(s) of cognitive deficits such ADHD, TBI, Alzheimer's disease or other dementia, stroke, previous chronic CNS infection or other neurological disorders
* Evidence of untreated major depression as by clinician interview or patient report
* Family history of suicide, major depression, or bipolar disorder
* Uncontrolled or labile hypertension (\> 135/85 mmHg), treated or untreated
* History of structural heart disease, including atherosclerosis or angina
* Diagnosis of bipolar disorder or a history of a psychotic episode
* Daily opioid use
* Daily benzodiazepine use other than nightly administration
* Use of other amphetamine or other sympathomimetic medication
* Use of naturally grown medicinal or non-medicinal marijuana more than 3x/week or 14x/month
* those with Hyperthyroidism or Glaucoma
* A history of drug abuse
* Known hypersensitivity to sympathomimetic amines
* A history of agitated or aggressive states
* Those taking monoamine oxidase inhibitors or other drugs that may interact with the study medication
* A known allergy to amphetamines or components of Adderall XR or container
* Past or present suicidal behavior or ideation
* Those with renal impairment or on nephrotoxic drugs.
* Have motion tics (hard to control, repeat twitching of any parts of the body) or verbal tics (hard to control repeating of sounds or words) or Tourette's syndrome
* Family history motion tics, verbal tics, or Tourette's syndrome
* Family history of sudden death, QT prolongation
* Positive pregnancy test
* Beck Depression Inventory - Fast Screen score question 7 marked 2 or 3 by participant, or scores in the severe range
