Immune inflammation may be a shared aetiological factor for mental disorders and CHD.14 Elevated inflammatory markers consistent with an acute-phase immunological response, especially C-reactive protein (CRP), interleukin-6 and tumour necrosis factor, are associated with MDD15 16 and an increased risk of cardiac morbidity and mortality.17 It has been suggested that antidepressants normalise proinflammatory states in depression and CHD.18 However, it is unclear whether depression is associated with poor sleep quality and cell-mediated immune function in patients with CHD. The gene discussed is CRP; the disease is psychiatric disorder.