Abstract Background The swift impact of the COVID-19 pandemic and ensuing restrictions on the mental health of the Belgian population prompted the need for a sustainable system to monitor its evolution. Repeated COVID-19 surveys were conducted between 2020 and 2022 to address this issue, followed by the launch of the BELHEALTH cohort project. Our study aims to analyze the trajectory of anxiety and depression at the post-pandemic period, using data from five waves of the BELHEALTH longitudinal surveys from October 2022 to March 2024. High-risk groups and the potential of social support and resilience to mitigate anxiety and depression were explored. Methods The BELHEALTH follow-up cohort of around 7,300 Belgian residents uses online surveys to assess anxiety (with the GAD-7), and depression (with the PHQ-9). The analyses were performed using linear mixed models on the 3,676 individuals who participated in all five waves. Results Preliminary results indicated that more people were affected by anxiety in October 2022 (16%) compared to June 2023 (14%), while depression rates were lower in October 2022 (13%) compared to February 2023 (14%) and March 2024 (15%). However, the trajectory of mental health varied across demographic subgroups, with worse outcomes observed among unemployed and younger individuals, as well as those living alone, in the Walloon Region (South of Belgium). Overall, people with a low level of resilience or a low level of social support exhibited higher odds of experiencing depression. Conclusions Reducing these social inequities in mental health necessitates the development of structural prevention measures and interventions at the regional level. These measures should target factors such as unemployment, which is particularly prevalent among younger individuals and those living in Wallonia. Additionally, fostering protective factors such as social support and resilience is crucial for mitigating mental health inequalities over time. Key messages • Monitoring mental health and its determinants remains crucial to identify and address social inequities, tailor interventions, and support vulnerable populations. • Unemployed, younger people, and those residing in the Walloon region are at particular risk.