Depression and other mood disorders are commonly experienced by people with multiple sclerosis.
MS-related depression is complicated by the fact that a person with MS is coping with a chronic illness that may be disabling and experiencing other cognitive changes. However, the depresion is separate from these other factors and often needs addressing as a unique problem.
Depression may respond to the use of antidepressants and other treatments.
People with multiple sclerosis may also experience other mood disorders. About 10% of people with MS suffer from more severe psychotic disorders such as manic-depression and paranoia. 5% may experience episodes of inappropriate euphoria and despair-unrelated to the patient's actual emotional state-known as "laughing/weeping syndrome." This syndrome is thought to be due to demyelination in the brainstem, the area of the brain that controls facial expression and emotions, and is usually seen only in severe cases.
Reference: The National Institute of Neurological Disorders and Stroke (NINDS)