Effects of seasonal mood changes on seasonal variations in coronary heart disease: role of immune system, infection, and inflammation.

Coronary heart disease shows a winter peak and summer trough in incidence and mortality. A substantial part of a general population experiences seasonal mood changes including winter depression. Many studies demonstrate that depression is associated with increased incidence, morbidity, and mortality of cardiovascular disease. Therefore, the author previously suggested that persons with high levels of seasonality may be at increased risk of developing or worsening of coronary heart disease in the winter. Some psychological factors promote the development of disorders of the cardiovascular system. The same psychological factors decrease immunity and promote infection. There is evidence that the infectious process is involved in the pathogenesis of coronary heart disease. Therefore, the author previously proposed that the development of infection and inflammation in the atherosclerotic plaque may be related to the psychological disorders that suppress the immune system. In this paper, the author suggests that winter depression-induced suppression of the immune system may contribute to the winter increase in incidence and mortality of cardiovascular disease.