How Much Do Mental Health and Substance Use/Addiction Affect Use of General Medical Services? Extent of Use, Reason for Use, and Associated Costs

Objective: To measure service use and costs associated with health care for patients with mental health (MH) and substance use/addiction (SA) problems.Methods: A 5-year cross-sectional study (2007-2012) of administrative health care data was conducted (average annual sample size = 123,235 adults aged >18 years who had a valid Ontario health care number and used at least 1 service during the year; 55% female). We assessed average annual use of primary care, emergency departments and hospitals, and overall health care costs for patients identified as having MH only, SA only, co-occurring MH and SA problems (MH+SA), and no MH and/or SA (MH/SA) problems. Total visits/admissions and total non-MH/SA visits (i.e., excluding MH/SA visits) were regressed separately on MH, SA, and MH+SA cases compared to non-MH/SA cases using the 2011-2012 sample ( N = 123,331), controlling for age and sex.Results: Compared to non-MH/SA patients, MH/SA patients were significantly ( P < 0.001) more likely to visit primary care physicians (1.82 times as many visits for MH-only patients, 4.24 for SA, and 5.59 for MH+SA), use emergency departments (odds, 1.53 [MH], 3.79 [SA], 5.94 [MH+SA]), and be hospitalized (odds, 1.59 [MH], 4.10 [SA], 7.82 [MH+SA]). MH/SA patients were also significantly more likely than non-MH/SA patients to have non-MH/SA-related visits and accounted for 20% of the sample but over 30% of health care costs.Conclusions: MH and SA are core issues for all health care settings. MH/SA patients use more services overall and for non-MH/SA issues, with especially high use and costs for MH+SA patients.