ObjectiveTo examine recent 12-year trends in the incidence of suicidal ideation (SI) and suicide attempts (SAs) and receipt of mental health treatment among individuals experiencing a past-year major depressive episode (MDE). Patients and MethodsUsing data from the National Survey of Drug Use and Health, we estimated the annual percentage of individuals with MDE who reported past-year SI or SAs and their use of mental health services from 2009 to 2020 and calculated odds ratios (ORs) for longitudinal change adjusting for potentially confounding factors. ResultsDuring our study period, the weighted unadjusted proportion of patients with a past-year MDE who reported SI increased from 26.2% (668,690 of 2,550,641) to 32.5% (1,068,504 of 3,285,986; OR, 1.38; 95% CI, 1.25 to 1.51) and remained significant in the multivariable-adjusted analysis (P<.001). The greatest increase in SI was seen among Hispanic patients, young adults, and individuals with alcohol use disorder. Similar trends were seen for past-year SAs, increasing from 2.7% (69,548 of 2,550,641) to 3.3% (108,135 of 3,285,986; OR, 1.29; 95% CI, 1.04 to 1.61), especially among Black individuals, patients with incomes greater than $75,000, and those with substance use disorders. In multivariable-adjusted analyses, the temporal trend of increasing SI and SAs remained significant (P<.001 and P=0.04, respectively). Among individuals with past-year SI or SAs, there was no notable change in the mental health service use, and over 50% of individuals with MDE and SI (2,472,401 of 4,861,298) reported unmet treatment needs. No notable differences were observed between 2019 and 2020, reflecting the coronavirus disease 2019 pandemic. ConclusionAmong individuals with MDE, rates of SI and SAs have increased, especially among racial minorities and individuals with substance use disorders, without a corresponding change in mental health service use.