Center for Health Policy and Research (CHPR) Publications


Substitution between Formal and Informal Care for Persons with Severe Mental Illness and Substance Use Disorders

UMMS Affiliation

Department of Family Medicine and Community Health; Center for Health Policy and Research; Clinical and Population Health Research



Document Type



Health Services Administration | Health Services Research | Public Health


BACKGROUND: Persons with severe mental illness (SMI) often get extensive informal care from family members and friends as well as substantial amounts of formal treatment from paid professionals. Both sources of care are well documented, but very little is known about how one affects the other.

AIMS OF THE STUDY: This analysis estimates the extent of substitution between direct care provided by family and friends and formal treatment for people with severe mental illness and substance use disorders. Separate estimates are generated for short-term and long-term effects.

METHODS: Data are from a randomized clinical trial conducted at seven mental health centers in New Hampshire between 1989 and 1995. The study includes detailed data for 193 persons with dual disorders measured at study entry and every six months for three years. Hours of informal care were compared with total treatment costs within each six-month period to measure short-term effects. Average amount of informal care over three years represented long-term caregiving practices. Measures of informal care are from interviews with informal caregivers. Treatment costs are based on combined data from management information systems, Medicaid claims, hospital records, and self reports. We used mixed effects repeated measures regression to estimate longitudinal effects and a multiple imputation technique to test the sensitivity of results to missing data.

RESULTS: In the short-term, persons with bipolar disorder used significantly more formal care as informal care increased (complementarity). The relationship between short-term informal and formal care was significantly weaker for persons with schizophrenia. For both diagnostic groups there was a long-term substitution effect; a 4-6% increase in informal care hours was associated with an approximate 1% decrease in formal care costs.

DISCUSSION: Although they must be confirmed by further research, these findings suggest that there is a significant and strong relationship between care given by family and friends and that supplied by formal treatment providers. The analysis indicates that the short-term relationship between informal care and formal treatment tends to be complementary, but differs according to diagnosis. Long-term effects, which are possibly related to changing role perceptions, show substitution between the two forms of care. Missing data for family care hours in some time periods was a concern in this study. However, the consistency in results between the analyses that used imputed data and the model using only original data increase our confidence in the findings. Although there may be some endogeneity between formal and informal care in other treatment settings we believe the unique characteristics of the service-rich environment in which this study was conducted limit that concern here.

IMPLICATIONS FOR HEALTH CARE PROVISION AND USE: The amount of care provided by informal caregivers has a significant impact on formal treatment costs. Models of care that explicitly acknowledge the interplay between the two types of care are needed to ensure efficient combinations of formal and informal care.

IMPLICATIONS FOR HEALTH POLICY FORMULATION: How to best to encourage informal support, without overburdening caregivers, is a key challenge facing policy makers and providers of mental health services. The merits of various approaches to reducing caregiver burden is a subject that needs more attention from researchers. In the interim, the demands on informal caregivers may mount as efforts to reduce health care spending continue.

IMPLICATIONS FOR FURTHER RESEARCH: Informal care is not often included in economic evaluations of mental health treatment. Although additional research is needed to understand better the mechanisms by which informal care and formal treatment are related, we believe our results offer a strong argument for including measures of informal care in future economic evaluations.

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Citation: J Ment Health Policy Econ. 2001 Sep 1;4(3):123-132.

Related Resources

Link to Article in PubMed