Sample and data collection
MULTIPLE SCLEROSIS
A retrospective cohort design was used. We analyzed data from the Partners Healthcare Research Patient Data Registry (RPDR), an EHR data warehouse covering 4.6 million patients from two large academic medical centers in Boston: Massachusetts General Hospital (MGH) and Brigham and Women’s Hospital (BWH), as well as other community and specialty hospitals in the Boston area, including McLean Hospital. All outpatient and inpatient hospital visits between 1998 and 2014, inclusive, at Partners Healthcare were included.Within the RPDR, 15,117 patients had a diagnosis of Multiple Sclerosis (ICD-9 of 340) and met our three inclusion criteria of: (1) three or more visits, (2) 30 days or more between first and last visits, and (3) at least one healthcare encounter recorded when the patient’s age was between 10 and 90 years. We collected all demographic, diagnostic, procedure, laboratory, and medication data for each visit. For the case cohort, all data recorded after the first instance of suicidal behavior were excluded.