Although individuals with lower socio-economic position (SEP) have a higher prevalence of mental health problems than others, there is no conclusive evidence on whether mental healthcare (MHC) is provided equitably. We investigated inequalities in MHC use among adults in Stockholm County (Sweden), and whether inequalities were moderated by self-reported psychological distress.

MHC use was examined in 31,433 individuals aged 18–64 years over a 6-month follow-up period, after responding to the General Health Questionnaire-12 (GHQ-12) in 2014 or the Kessler Six (K6) in 2021. Information on their MHC use and SEP indicators, education, and household income, were sourced from administrative registries. Logistic and negative binomial regression analyses were used to estimate inequalities in gained MHC access and frequency of outpatient visits, with psychological distress as a moderating variable.

Individuals with lower education or income levels were more likely to gain access to MHC than those with high SEP, irrespective of distress levels. Education-related differences in gained MHC access diminished with increasing distress, from a 74% higher likelihood when reporting no distress (odds ratio, OR = 1.74 [95% confidence interval, 95% CI: 1.43–2.12]) to 30% when reporting severe distress (OR = 1.30 [0.98–1.72]). Comparable results were found for secondary care but not primary care i.e., lower education predicted reduced access to primary care in moderate-to-severe distress groups (e.g., OR = 0.63 [0.45–0.90]), and for physical but not digital services. Income-related differences in gained MHC access remained stable or increased with distress, especially for secondary care and physical services.

Among MHC users, we found marginal socio-economic differences in the frequency of outpatient visits, and these differences decreased with increasing distress. Yet, having only primary education with severe distress was associated with fewer outpatient visits compared with having post-secondary education (rate ratio, RR = 0.82; 95% CI: 0.67–1.00). These inequities were especially evident among women and for visits to psychologists, counsellors, or psychotherapists.

Although lower-income groups used services more than others, they still had higher odds of not using services when reporting distress (i.e., those not in contact with services despite scoring ≥3 on the GHQ-12 or ≥8 on the K6; OR = 1.27; 95% CI: 1.15–1.40).

Overall, individuals with lower education and income used MHC services more than their counterparts with higher socio-economic status; however, low-educated individuals faced inequities in primary care and underutilized non-physician services such as visits to psychologists.