Publisher Summary This chapter provides an overview of the current knowledge and implications for future research in the cognitive and psychiatric disorder. Effective strategies for managing cognitive dysfunction (CD) have led to trials with pharmacologic agents and cognitive rehabilitation. In multiple sclerosis (MS), CD typically consists of domain-specific deficits. CD can have a dramatic impact on several aspects of quality of life, independently of the degree of physical disability, affecting the ability to maintain employment, daily living activities, and social life. Cognitive impairment can limit the capacity of the patient to benefit from inpatient rehabilitation. Impaired attention and reduced information processing speed may represent a sensitive indicator of incipient CD. CD in MS encompasses all disease stages and clinical phenotypes. There are modest correlations between the presence or degree of CD and disease duration, disability level as mea­sured on the expanded disability status scale (EDSS), and disease course. Psychiatric disorders are dedicated to depression, because it is the most frequent problem in MS patients. Depression in MS is associated with the risk of suicide. Euphoria is characterized by a persistently cheerful mood and overly optimistic state of mental and physical well-being despite significant neurologic disability. Pseudobulbar affect, also known as emotional lability, is characterized by frequent and inappropriate episodes of crying, laughing or both.