Mental healthcare expenditure among adults by type of mental healthcare and its association with age and sex in the Netherlands between 2015 and 2020.

We aimed to explore temporal patterns of mental healthcare expenditure over the period 2015-2020 by age and type of mental healthcare, as well as by sex. A records-based cohort study using comprehensive data from health insurers in the Netherlands at the 4-number postal code level was performed. We used cluster-weighted linear regressions to examine temporal patterns of mental healthcare expenditure by age group (young: 18-34 vs old: 35-65), sex, and type of care. We examined the interaction of age with sex by adding the interaction between age, year, and sex to the model. The predicted costs were higher for ages 18-34 compared to older adults aged 35-64 for all mental healthcare costs except general practitioner mental healthcare (GP-MHC). The baseline regression coefficient for the young age group was 0.23 (95%-CI = 0.21;0.24) for all mental healthcare costs combined, 0.22 (95%-CI = 0.21;0.24) for specialized mental healthcare (SPECIALIST-MHC), 0.08 (95%-CI = 0.07;0.09) for basic mental health care (BASIC-MHC) and -0.02 (95%-CI = -0.03;-0.01) for GP-MHC. There was evidence for an interaction between age and year (p < 0.0001). Women had higher mental healthcare costs than men at all time points. We found an interaction between age, sex and year (p < 0.0001), with a stronger increase in the age-cost association SPECIALIST-MHC in women, while men showed a lower but more strongly increasing age-cost association for BASIC-MHC and GP-MHC. Our study found that while young women represent an increasing share of SPECIALIST-MHC, BASIC-MHC, and GP-MHC show a stronger rise in costs for young men. Future research should address whether this is due to an overlooked need for care among young men.