Mood Disorder in Multiple Sclerosis

To the Editor. —Few investigators would argue that depression occurs to varying degrees in patients with multiple sclerosis (MS). In a recent article, however, Joffe and colleagues¹concluded that patients with MS have "... a very high prevalence of affective illness," and, consequently, that mood disorder and MS "... may share common neurologic and biochemical mechanisms" (p 378). We believe that flaws in their research methodology may have rendered their conclusions somewhat premature. The following summarizes our objections: Psychiatric diagnosis is inherently subjective and influenced by potentially biased a priori scientific hypotheses (eg, patients with MS have a higher prevalence of mood disorder than other chronic, non-central nervous system illnesses). It is noteworthy that the investigators did not employ a control group. The addition of a control group would have allowed assessment interviews in which the examiner could have been blinded to knowledge of the patient's diagnosis. In a related vein