Two key concepts in the life course approach in medicine: allostatic load and cumulative life course impairment

According to the biopsychosocial model, psychosocial and biological factors interact in a number of ways influencing onset and course of medical disease. In a longitudinal perspective, such factors may elicit different effects on health depending on their accumulation mechanisms and timing of exposure over the life course. These aspects have become particularly relevant in the field of chronic diseases such as chronic dermatological conditions, where complete healing is unlikely to occur. Two key concepts may aid understanding of chronic medical conditions in a more comprehensive manner. In the first place, the concept of allostatic load may represent the link between the cumulative effect of various challenging situations and the disease onset through the progressive 'wear and tear' induced by chronic exposure to fluctuating allostatic responses. In addition, the allostatic overload model emphasizes the fact that the cumulative interaction of stressors, psychological symptoms and impaired psychological well-being may constitute a danger to health. In the second place, the concept of cumulative life course impairment, which takes into account the multiple dimensions of chronic disease, underlines the fact that illness is only one of many recordable parameters which ultimately determine, through their mutual interaction, the 'life trajectory of individuals'. In a broader sense, both concepts of allostatic load and cumulative life course impairment allow more light to be shed on a new perspective on illness - the life course perspective - and on its interactions with psychological, social and environmental factors. This perspective may ultimately result not only in a substantial improvement of clinical care, but also in a different and long-lasting approach to interventions in chronic illness, with wide economic, political and social consequences whose entity has yet to be appreciated.