The neurobehavioral aspects of multiple sclerosis include both cognitive disturbances and neuropsychiatric disorders. Cognitive difficulties in multiple sclerosis involve memory retrieval, mental processing speed, reasoning and goal-oriented behavior, verbal fluency, and visuospatial skills. Cognitive slowing has been observed to be significantly associated with brain volume loss and global gray matter atrophy, and hippocampal atrophy correlates with memory encoding impairments. Neuropsychiatric disturbances are primarily mood disorders. Depression may present as an early sign in multiple sclerosis and may be followed by cognitive impairment before physical disability appears. Severity of cognitive impairment significantly correlates with physical disability and with depression severity.