Multiple sclerosis (MS) patients are known to be at increased risk from mood disorders and suicidal ideation. Although these are often associated with alcohol disorders, the drinking habits of MS patients have not been well studied to date. Our study assessed drinking patterns in 140 MS patients, focusing on a possible link between problem drinking and mood and anxiety disorders. Lifetime psychiatric diagnoses were ascertained using the Structured Clinical Interview for DSM-IV disorders (SCID-IV). Results demonstrate that one in six MS patients drink to excess over the course of their lifetime. Those with a history of problem drinking display a higher lifetime prevalence of anxiety (P = 0.006), but not mood disorders. There were also significant associations between problem drinking and a lifetime prevalence of suicidal ideation (P = 0.006), substance abuse (P = 0.001), and a family history of mental illness (P = 0.008). Clinicians should be aware of the possibility of problem drinking in MS patients, and how this may complicate the course of their disease. Clues to problem drinking in MS patients are the presence of a positive family history of mental illness and prominent anxiety.