Delirium and depression: inter-relationship and clinical overlap in elderly people.

Delirium and depression are complex neuropsychiatric syndromes common in the elderly and are associated with poor health-care outcomes. Accurate diagnosis is essential to the provision of optimum health care for individuals with these conditions but is complicated by substantial clinical overlap in symptoms and comorbidities. A careful assessment of the patient's symptoms, including their context and time course, is needed for accurate diagnosis. Previous depression is common in patients with delirium and depressive illness is a recognised sequelae of delirium. The two syndromes seem to be caused by similar pathophysiological mechanisms, involving disturbances in stress and inflammatory responses, monoaminergic and melatonergic signalling, which point to new avenues for therapeutic intervention. Improved methods to assess delirium and depression in populations at high risk by virtue of their age, diminished cognitive reserve and physical frailty is a key target to achieve improved health-care outcomes in elderly individuals.