Use of outpatient somatic health services by patients who use or need mental health services in three provider plans.

A major topic in mental health (MH) research addresses the problem that patients who use mental health services have inappropriately high levels of somatic use, and examines whether provision of mental health services can decrease the inappropriate use (the so-called offset effect). However, the research showing higher somatic use by mental health patients has usually been unable to control for the patients' health status, or for their mental health status. In this paper we examine use of somatic health services by enrollees in three provider plans as a function of both mental health use and mental health need. In two of the provider plans (an HMO and a prepaid independent practice association), MH users used significantly more outpatient somatic services than non-MH patients, after control for age and sex, and after control for the number of chronic conditions they had. People with MH need, however, did not use significantly more MH services than those without MH need. In the third plan, a Blue Cross/Blue Shield type of plan, results were different; MH users did not have significantly higher somatic utilization after control for chronic conditions, and those with MH need did have significantly higher somatic utilization after control for age and sex, but not after control for the number of chronic conditions. These results suggest that the form of inappropriate use of outpatient somatic services, and the nature of an offset effect, may be specific to the type of insurance provided.