Multiple sclerosis (MS) likely begins years before the first neurological symptom by a set of not-clearly defined, subtle symptoms, leading patients to increasingly seek medical attention years before diagnosis. Some may even require psychiatric care during this period. This phase of the disease is known as the MS prodrome. Our plan is to better characterize psychiatric healthcare encounters during this phase of the disease by analyzing anonymized and linked administrative health data that is generated whenever an individual visits a doctor, is admitted to a hospital, or fills a prescription at a pharmacy. We aim to specifically look at any visits resulting in a diagnosis of depression, anxiety, or bipolar disorder by a physician, any visits to psychiatrists, and also look at prescriptions filled for medications, such as antidepressants. These 'psychiatric data' generated during the five years before patients' first MS symptom will be explored and compared to that of individuals from the general population. We believe that advancing our understanding of the MS prodrome may help us identify patients sooner in their disease course, allowing for earlier treatment, and eventually prevent disease progression.