From pre-pandemic to pandemic: unravelling mental health trajectories in clinical and general population cohorts.

AIMS: The COVID-19 pandemic is often portrayed as a universal mental health crisis, especially in studies lacking pre-pandemic data. Research including pre-pandemic assessments nonetheless yields mixed results, making the pandemic's impact unclear, particularly when considering differences between general and clinical populations (defined as individuals with prior mental disorder diagnoses). This study examined depression and anxiety trajectories from pre-pandemic to pandemic phases in general and clinical populations. It also explored how symptom trajectories varied by sociodemographic and pandemic-related factors. METHODS: In the current study, we drew on three general-population cohorts from Germany and France (n = 1,813) that had previously been harmonized within the Co-RESPOND project. We additionally harmonized and integrated three clinical cohorts from the Netherlands (n = 1,069) into this pooled dataset. Cohorts were included in the present study if they provided pre-pandemic baseline data and at least two assessments during the pandemic. Anxiety and depressive symptoms were measured using validated instruments and transformed into z-scores to enable cross-cohort comparability. Symptom trajectories were identified separately for general-population and clinical cohorts using latent growth mixture modelling, and logistic regressions were used to examine factors associated with trajectory membership. RESULTS: Participants in the general-population sample had a median age of 39.8 years, while those in the clinical sample had a median age of 57.4 years. Women accounted for 64.6% of the general-population group and 67% of the clinical group. In the general population, approximately 80% showed decreasing symptoms, including those with higher initial severity, while 20% maintained low levels. Divorce/separation and having children were related to more favourable anxiety and depression trajectories, while older age and childcare burden were associated with less favourable trajectories of depressive symptoms. In the clinical population, approximately half improved from moderate symptom levels, with the remainder exhibiting consistently high or low symptoms. Being in a relationship, older age and being a man were linked to more favourable anxiety trajectories. CONCLUSIONS: This study provides substantial evidence that the COVID-19 pandemic did not lead to a uniform deterioration in mental health, as most adults across both general and clinical populations experienced stable or improving symptoms. Our findings underscore the need for mental health surveillance and differentiated, proportionate responses that reflect diverse symptom patterns and risk profiles.