Study aim: 1.Determining the frequency of cognitive disorders in the study population in the group of Atomoxetine and Placebo 2.Comparison of changes in cognitive impairment before and after drug administration between Placebo and Atomoxetine Design: Clinical trial with control group,double blind, randomized, phase 3 ,with a parallel group design of 52 patients. For randomization, a randomized block method with 4 blocks was used Settings and conduct: .Patients referred to outpatient or inpatient clinics of Golestan Hospital in Ahvaz are selected after reviewing the inclusion and exclusion criteria. Initially, McFims test patients are taken in a double-blind study. The number of each patient is placed on the drug package based on the software randomization list. Also, two placebo and Atomoxetine drugs are packaged in such a way that the patient does not know the name of the drug and is given to patients by a nurse not related to the research. In such a way that the attending physician is not aware of the medication provided to each patient.Group A, which consists of 26 patients selected by an uninformed person, will be treated with Atomoxetine for three months, and group B, which includes 26 patients, will be treated by an uninformed person. Will be selected and treated with placebo. At the beginning and end of 3 months, McFims test is performed for patients. Participants/Inclusion and exclusion criteria: Entry requirements; Age between 18 and 55 years; Testable measurable cognitive impairment McFims attributed to multiple sclerosis; Diagnosis of multiple sclerosis based on McDonald's criteria No entry conditions; Continuous use of stimulants; Contraindications to the use of Atomoxetine Intervention groups: Group A will be treated with Atomoxetine and group B will be treated with Placebo Main outcome variables: Language; executive function; processing speed ; functional memory; new learning power