This research article scrutinises the psychosocial underpinnings that influence adherence to treatment among patients with chronic diseases, assuming that adherence is a multifaceted phenomenon shaped by a complex set of psychosocial factors. Purpose: the aim of the study is to uncover the complex relationship between these factors and adherence to treatment, using linear sampling to capture the dynamics and temporal evolution of adherence behaviour in the context of chronic illness. Materials and methods. Using a rigorous methodological framework, participants with many chronic conditions were included in the study, with inclusion and exclusion criteria carefully developed to ensure a representative and diverse group. The study utilised a range of validated psychometric tools to quantify psychosocial variables such as social support, stress levels and health beliefs, as well as a multifaceted approach to assess adherence combining self-report, pharmacy records and biometric measures. Advanced statistical analyses, including mixed-effects models and structural equation modelling, were used to identify relationships between psychosocial factors and adherence to treatment, taking into account the complexity and longitudinal nature of the data. Results. The findings highlight the critical role of social support in increasing treatment adherence as well as the detrimental effects of elevated stress levels, emphasising the critical interplay between individual psychological resilience and external support systems. The study also clarifies the influence of health beliefs and illness perceptions on adherence behaviour, advocating a better understanding of the cognitive and affective dimensions that determine patients’ engagement in treatment. Findings. The article concludes by arguing that a paradigm shift towards integrating psychosocial support mechanisms into holistic models of care is needed to increase adherence in chronic disease management. It calls for the implementation of health care policies and practices that not only address the biomedical aspects of chronic disease, but also the psychosocial complexities inherent in long-term disease management. Findings from the study encourage further research into specialised psychosocial interventions aimed at improving adherence and consequently quality of life for people coping with the challenges of chronic illness.