Depression prevalence estimates in Spain (1995-2021): a systematic review.

Introduction: This study aimed to systematically review and synthesise heterogeneous depression prevalence estimates in the Spanish general population and analyse their variation according to methodological factors over recent decades. Content: Searches were conducted in MEDLINE, Embase, Web of Science, Scopus, PsycINFO, ÍnDICEs CSIC, and PSICODOC. Inclusion criteria were: reporting incidence, prevalence, or mean depression scores; population ≥14 years; n ≥1,000; use of validated assessment methods. The review followed PRISMA 2020 guidelines. Study quality was assessed using the Joanna Briggs Institute tool. Findings were synthesised qualitatively. 13 studies were included; most were international (n=7), cross-sectional (n=11), and used diagnostic interviews (n=8). Comparable studies (n=11) showed an increase in prevalence estimates in recent years, ranging from approximately 4-22 %, depending on assessment method and study period. Several studies (n=7) reported significant associations with female gender and unfavourable sociodemographic conditions. Most studies (n=11) were high quality. Summary: Evidence derived from heterogeneous estimates suggests an increase in reported depression prevalence among comparable studies from 1995 to 2021. Despite methodological variation, women were affected twice as often as men, and unfavourable sociodemographic conditions were linked to higher risk. Early-pandemic increases likely reflect reactive psychological distress. This is the first systematic review on this topic. Outlook: Future research should use probability sampling and harmonised screening and diagnostic methods to improve representativeness and comparability.