Classification & Assessment in Psychiatry · Paper A
Delirium: features and assessment
Delirium matters because it is a medical emergency masquerading as a psychiatric problem, and missing it costs lives, so recognising it fast changes management immediately. It is an acute, fluctuating disturbance of consciousness and attention, usually caused by an underlying physical illness or drug effect. For example, imagine a hospitalised older man who is lucid in the morning but confused and agitated by evening, unable to hold a conversation for more than a few seconds. In practice, that fluctuating course over hours, combined with poor attention, is the hallmark that should trigger a search for delirium's underlying cause.
The hallmark feature of delirium is inattention, an inability to focus, sustain, or shift attention normally, tested at the bedside by asking the patient to recite the months of the year backwards. Delirium is classified as hyperactive (agitated, restless, sometimes hallucinating), hypoactive (withdrawn, quiet, drowsy), or mixed. Hypoactive delirium is frequently missed because the patient appears merely tired or depressed rather than obviously unwell, and it carries a worse prognosis than the more visible hyperactive form. The 4AT (a rapid four-item bedside test) and the CAM (Confusion Assessment Method) are validated screening tools used to detect delirium quickly on the ward. Picture a quiet, withdrawn patient assumed to be simply depressed after surgery, who is later found, on formal testing, to be profoundly inattentive. In practice, using a structured tool like the 4AT catches this quiet, hypoactive presentation that a brief informal chat would otherwise miss.