Psychiatric Comorbidity During the Prodromal Period in Patients With Multiple Sclerosis.

Background And Objectives: Psychiatric morbidity is common after a multiple sclerosis (MS) diagnosis. However, little is known about psychiatric comorbidity during the prodromal phase (before MS onset). To compare the prevalence and relative burden of psychiatric morbidity in individuals with MS with matched controls before MS onset.

Methods: Using linked administrative and clinical data from British Columbia, Canada, we identified cases with MS through a validated algorithm or from neurologist-diagnosed MS clinic attendees. Cases were matched by age, sex, and geographical location with up to 5 general population controls. We identified psychiatric morbidity through a validated definition and determined its prevalence in cases/controls in the 5 years before the first demyelinating claim of cases with MS ("administrative cohort") or symptom onset ("clinical cohort") and estimated case/control prevalence ratios with 95% CIs. We also compared the yearly number of physician visits for psychiatric morbidity, visits to psychiatrists, psychiatric-related admissions, and psychotropic dispensations pre-MS onset in cases/controls regardless of whether psychiatric morbidity algorithm was fulfilled using negative binomial regression fitted through generalized estimating equations; results were reported as adjusted rate ratios with 95% CIs. We assessed yearly trends through interaction terms between cases/controls and each year pre-MS onset.

Results: The administrative cohort comprised 6,863/31,865 cases/controls; the clinical cohort comprised 966/4,534 cases/controls. Over the entire 5-year period pre-MS onset, 28.0% (1,920/6,863) of cases and 14.9% (4,738/31,865) of controls (administrative cohort) had psychiatric morbidity, as did 22.0% (213/966) of clinical cases and 14.1% (638/4,534) controls. Psychiatric morbidity prevalence ratios ranged from 1.58; 95% CI 1.38-1.81 (clinical cohort) to 1.91; 95% CI 1.83-2.00 (administrative cohort). In the administrative cohort, health care use was higher for cases in each year pre-MS onset (all 95% CIs >1); physician visits were 78% higher in year 5 pre-MS onset and 124% 1 year before; visits to psychiatrists were 132% higher in year 5 and 146% in year 1; hospitalizations were 129% higher in year 5 and 197% in year 1; and prescription dispensations were 72% higher in year 5 and 100% in year 1. Results were not significant in the clinical cohort.

Discussion: Psychiatric morbidity represents a significant burden before MS onset and may be a feature of the MS prodrome.