Background
Depression and anxiety are major mental health challenges affecting millions of United States (U.S.) children, with an estimated annual societal cost of $247 billion. Surveys indicate increasing rates of these disorders, but there is limited knowledge about clinically diagnosed cases, especially during the coronavirus disease (COVID-19) pandemic. Notably, clinical diagnosis rates are often lower than self-reported rates from surveys. Understanding disparities and long-term impacts is crucial, as well as exploring the underlying causes of this rise in mental health conditions among youths. Further research is necessary to address these gaps and improve interventions for managing depression and anxiety in children and adolescents, particularly in the context of the pandemic’s impact on mental health.

About the Study
This population-based cohort study involved members aged 5 to 22 enrolled in Kaiser Permanente Southern California (KPSC) from 2017 to 2021. A total of 1,703,090 unique members were identified, with approximately 1 million members per calendar year. Kaiser Permanente’s extensive electronic medical records (EMR) system provided the data for this study, which was approved by the KPSC Institutional Review Boards. Individual participant consent was waived due to the minimal risk involved.

The study found that weight status, particularly obesity for depression and underweight for anxiety without depression, was a stronger predictor of mental health outcomes than income or ethnicity.

Depression diagnoses were based on clinical encounters with International Statistical Classification of Diseases, Tenth Revision (ICD-10) codes corresponding to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria for major depressive disorder (MDD) and dysthymia. Anxiety diagnoses were identified using ICD-10 codes for generalized anxiety disorder, panic disorders, social anxiety disorder, and other phobia-related conditions. Both inpatient and outpatient records were analyzed, and prior studies have validated these codes for identifying depression and anxiety.

Subgroup analysis was performed based on age, gender, race, ethnicity, weight status, household income, and comorbidity history. Incidence and prevalence rates were calculated, and trends over time were assessed using Poisson regression, including comparisons before and during the COVID-19 pandemic.

Study Results
The study included over 1.1 million members aged 5 to 22 in each year from 2017 to 2021, with a total of 1,703,090 unique participants. The average age was 14 years, with approximately 30% aged 5 to 10.9 years, 16% aged 11 to 13.9 years, 22% aged 14 to 17.9 years, and 31% aged 18 to 22.9 years during the study period. About 51% of participants were male, and 49% were female. Across the years, the racial and ethnic composition was consistent: roughly 50% were Hispanic, 8% non-Hispanic Black, 8% non-Hispanic Asian, 23% non-Hispanic White, and the remainder identified as other groups. Additional demographic data, such as household income and health insurance status, were also included.

The incidence of depression rose significantly from 1.35% in 2017 to 2.10% in 2021, a 55.6% increase. The rates were consistently highest among older age groups (14 to 22 years), females, and individuals with higher income, obesity, or comorbidities. Weight status, specifically obesity, was one of the most important factors influencing depression rates. Notably, the increase during the COVID-19 pandemic was higher (1.97%) than before (1.56%), although the rate of increase per year during the pandemic was not significantly greater than pre-pandemic trends. The prevalence of depression also increased, rising from 2.55% in 2017 to 4.08% in 2021. Subgroup analysis mirrored trends in incidence, with notable increases among individuals aged 18 to 22 years and those aged 14 to 17 years.

The research highlights the importance of school environments in shaping mental health trends, as the age groups correspond to key educational stages like elementary, middle school, and college life.

The incidence of anxiety without depression also increased, from 1.77% in 2017 to 2.32% in 2021, a 31.1% rise. Similar to depression, the incidence of anxiety without depression was highest among older age groups, females, and non-Hispanic White individuals. Weight status, particularly being underweight, was a key factor influencing anxiety without depression. The prevalence of anxiety without depression rose from 3.13% in 2017 to 4.22% in 2021, with significant increases during the pandemic compared to pre-pandemic years. In both depression and anxiety, weight status and age were major factors contributing to the outcomes, alongside gender, race and ethnicity, and comorbidity.

Conclusions
To summarize, the study found a significant increase in clinically diagnosed depression and anxiety without depression from 2017 to 2021, with higher rates during the COVID-19 pandemic. While depression rates increased during the pandemic, the rate of increase per year was similar to pre-pandemic trends. Depression was more common in older adolescents, females, those of American Indian or Alaska Native, non-Hispanic White, or multiple races, and those with higher income, obesity, or comorbidities. Anxiety without depression was also higher in those with underweight. The findings highlight the need for targeted mental health interventions, particularly as the pandemic exacerbated rising trends in youth mental health issues.