General MedicineTier 2Disease (DEADMAN)

Psychiatry - mental health manifestations of systemic disease

Description

Systemic medical conditions can directly cause or mimic psychiatric symptoms - thyroid dysfunction causing mood/anxiety symptoms, corticosteroid-induced mood disturbance, delirium from numerous medical causes mimicking psychosis or depression, and several autoimmune/neurological conditions presenting with prominent psychiatric features - making it essential to consider an organic medical cause before attributing new psychiatric symptoms purely to a primary psychiatric diagnosis, particularly with an atypical presentation

Relevant to any new or atypical psychiatric presentation, particularly in a patient without a prior psychiatric history, older patients, or where symptoms have an unusual pattern/rapid onset atypical for the suspected primary psychiatric diagnosis

Multiple systemic conditions directly affect brain function through various mechanisms (hormonal, metabolic, autoimmune, direct structural/inflammatory CNS involvement), explaining why psychiatric symptoms can be the presenting or dominant feature of an underlying medical condition rather than a primary psychiatric disorder - recognising this possibility prevents inappropriate psychiatric-only treatment of what is actually a treatable underlying medical condition

New psychiatric presentation, particularly with atypical features, older age of onset, rapid progression, or without a prior psychiatric history, should prompt screening for organic causes (thyroid function, basic metabolic panel, medication review, and further targeted investigation as clinically indicated)
Delirium should always be actively considered and distinguished from a primary psychiatric presentation, particularly in acutely unwell or hospitalised patients, given its distinct underlying causes and management approach

Identified organic cause -> treating the underlying medical condition, which may substantially or fully resolve the psychiatric symptoms, rather than treating the psychiatric symptoms in isolation with psychotropic medication alone
Ongoing psychiatric symptom monitoring alongside treatment of the identified organic cause, given symptom resolution may lag behind treatment of the underlying condition

Thyroid dysfunction and mood/anxiety symptoms, corticosteroid-induced mood disturbance, delirium mimicking psychiatric presentations, autoimmune/paraneoplastic neuropsychiatric syndromes (e.g. anti-NMDA receptor encephalitis) as important, treatable organic mimics

New psychiatric symptoms, particularly with an atypical presentation, older age of onset, or rapid progression, should prompt active screening for an underlying organic medical cause before treatment proceeds on the assumption of a primary psychiatric disorder - several treatable medical conditions can present predominantly or exclusively with psychiatric features, and missing this possibility delays appropriate treatment of the actual underlying cause

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