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

Delirium and depression are complex neuropsychiatric syndromes that are common in the elderly and associated with a variety of poor healthcare outcomes. Accurate detection is key to providing optimal care for these conditions but is complicated by their considerable clinical overlap. This includes shared symptom profiles as well as comorbidity. Careful assessment of symptom character as well as the context and course of disturbances can allow for more accurate diagnosis. Prior depressive illness is a common finding in patients with delirium, while depressive illness is a recognised sequel of delirium. Evidence points to similar pathophysiological mechanisms involving disturbances in stress and inflammatory responses, monoaminergic and melatonergic functions, that in turn point to avenues for therapeutic intervention. Development of better tools for systematic assessment for delirium and depression in populations at high risk by virtue of age, diminished cognitive reserve and frailty is a key target to achieve improved healthcare outcomes.