Patient cost-sharing, mental health care and inequalities: A population-based natural experiment at the transition to adulthood.

BACKGROUND: Patient cost-sharing has been increasing around the world, despite the evidence that it reduces both unnecessary and necessary health care utilisation. Financial barriers could compound to poor transitional care into adulthood, when forgoing mental health treatment may have long-term consequences on health and development. We evaluate the impact of increasing deductibles on mental health care use by young adults, and the heterogeneous effects for vulnerable groups. METHODS: We use individual administrative records for 1,541,210 individuals between 17 and 19 years of age, living in the Netherlands. We implement a difference-in-discontinuity design that exploits an increase in the deductible of about 180 euros, between 2009 and 2014, and the deductible exemption for those below 18 years old. Finally, we study subgroup effects by household income, level of mental health care expenditure and medication use for mental disorders. RESULTS: Our results show that increasing deductibles reduced the probability of mental health care use at the transition to adulthood by 13.6% for females (-13.6%, CI 95%: -22.1%, -5.2%), and by 5.3% for males (-5.3%, CI 95%: -11.8%, 1.2%). The reduction was larger among females in the lowest (-18.9%, CI 95%: -35.4%, -2.3%) and second lowest (-21.3%, CI 95%: -36.7%, -5.9%) income quartiles. Additionally, we find increased treatment cessation in high deductible years to happen across all levels of mental health care need. CONCLUSIONS: Our findings indicate that cost-sharing is compounding to existing disruptions in care at the transition between children/adolescent and adult services. The larger reductions in mental health care use among low-income females uncover the role of the deductible increase in widening mental health care inequalities. Increased treatment cessation even among high-intensity users suggests potential long-term consequences for individuals, the health system, and society.