Estimating trends in serious psychological distress and depression among 18- to 64-year-olds in the United States from 2004 to 2019 using K6 and PHQ scales.

BACKGROUND: Information from large national surveys is potentially useful for examining trends in mental health, but prior research has obtained inconsistent findings. This study attempts to determine whether Kessler 6 and Patient Health Questionnaire measures from different surveys consistently indicate trends in serious psychological distress or depression.

METHODS: Annual rates of serious psychological distress or depression were computed for 18- to 64-year-olds from 2004 to 2019 or sub-periods from four major household surveys based on values of Kessler 6, Patient Health Questionnaire 2, and Patient Health Questionnaire 9 scales. The observed trends were then compared to those from four potential consequences of poor mental health.

RESULTS: The potential consequences of poor mental health increased over time, as did serious psychological distress measured by the Kessler K6 in the National Health Interview Survey and National Survey on Drug Use and Health, and serious depression using Patient Health Questionnaire 2 and 9 data from the National Health and Examination Survey. Conversely, rates of serious psychological distress/depression, proxied by Kessler 6 and Patient Health Questionnaire 2 scores from the Medical Expenditure Panel Survey fell sharply after 2012.

CONCLUSIONS: The mental health of prime-age US adults almost certainly deteriorated from 2004 to 2019 but, when based on Kessler 6 and Patient Health Questionnaire scales, the results from some high-quality national household surveys indicated the opposite trends, exhibited substantial year-to-year variation, or had large confidence intervals. This highlights the need for considerable care in estimating trends in serious psychological distress or depression, even when using high-quality surveys.