Patient description: A 46-year-old Asian woman with MDD complains of persistent feelings of sadness and loss of interest in daily activities. She states that her mood is still depressed most of the days. She complains of loss of energy and feelings of worthlessness nearly every day. She is on anti-depressants for the past 6 months, but the symptoms are still present. She does not drink alcohol or smoke. She used to exercise every day for at least 30 min., but she doesn't have enough energy to do so for the past 3 weeks. She also has some digestive issues recently. She is married and has 4 children. She is menopausal. Her husband was diagnosed with colon cancer a year ago and is undergoing chemotherapy. Her past medical history is unremarkable. Her family history is negative for any psychologic problems. Her HAM-D score is 20.

Clinical trial eligibility criteria: eligible ages (years): 18.0-55.0,  Major Depressive Disorder Cognitive Impairment Diagnostic and Statistical Manual (DSM)-5 for past Major Depressive Episode within MDD, confirmed through Mini-International Neuropsychiatric Interview (MINI) diagnosis 2. Age between 18 and 55 years 3. Montgomery-Åsberg Depression Rating Scale < 7 (in remission) 4. Ability to read and understand English 5. Participant has been treated with an antidepressant for ≥ 6 months prior to enrolment 6. Participant agrees to remain on a stable antidepressant regimen for the duration of the trial (8 weeks) 7. Participant is currently experiencing cognitive deficits, as confirmed by an NCI >1 standard deviation below the mean on CNS Vital Signs cognitive battery 8. Women of child bearing potential must agree to use birth control for the duration of the study and 1 month following discontinuation of the study drug  Pregnancy/lactation 2. Lifetime history of Bipolar I, II or psychosis; other comorbidities (e.g. Generalized Anxiety, Panic Disorder) may be allowed by clinician judgement 3. Subject has current clinical diagnosis of autism, dementia, intellectual disability, or mild cognitive impairment 4. Meets DSM-5 for active Post-Traumatic Stress Disorder, confirmed through MINI diagnosis 5. Subject meets for current personality disorder 6. Concomitant use of monoamine oxidase inhibitors and/or other psychotropic drugs including lithium, clomipramine, and triazolam 7. Recent (< 6 months) stimulant use, such as medications used for attention deficit hyperactivity disorder 8. Subject is taking antipsychotics 9. Subject is taking herbaceuticals (i.e. natural products that have psychoactive properties, such as St. John's wort) 10. Concomitant use of medications that may interact with modafinil, including warfarin and cyclosporine 11. Medical condition requiring immediate investigation or treatment 12. Recent (< 6 months)/current history of drug abuse/dependence (other than caffeine or nicotine) 13. Previous intolerance or failure to respond to an adequate trial of modafinil 14. Any past history of head injury or concussion, as confirmed by the Ohio State University Traumatic brain injury (TBI) Identification Short Form 15. Current suicidal ideation (MADRS Item 10 ≤2 or by clinician judgement) 16. History of coronary artery disease, recent (<1 year) myocardial infarction, or unstable angina 17. History of left ventricular hypertrophy, ischemic ECG changes, chest pain, arrhythmia, or clinically significant manifestations of mitral valve prolapse in association with use of CNS stimulants 18. Involvement in another treatment study during the time of the study