Foundations and Psychiatric Assessment in the Medically Ill
Framing the assessment
In the medically ill, the first task is to distinguish primary psychiatric illness from a medical or substance-induced syndrome, and to separate delirium from dementia and depression. Any acute change in attention or arousal is delirium until proven otherwise; the hypoactive form is commonly mistaken for depression. Collateral information and the chart (medication changes, metabolic derangement, infection) matter as much as the interview.
Interviewing must accommodate the setting: shorter sessions, symptom-anchored questions, cognitive screening embedded in the encounter, and attention to sensory deficits, pain and fatigue. Use validated instruments for what they are, screens rather than diagnoses. PHQ-9 somatic items inflate scores in the medically ill; weight the cognitive-affective items and functional change. The MMSE is insensitive to executive dysfunction and ceiling-prone; the MoCA and bedside tasks (verbal fluency, clock drawing, Luria three-step, Trails B) sample frontal-executive function better.
Testing
Order tests to answer a differential, not as a reflex panel: TSH, B12, CBC, CMP, glucose, calcium; HIV and syphilis serology where risk or unexplained cognitive change exists; urine drug screen; cortisol with Cushingoid features; autoimmune and paraneoplastic panels plus NMDA-receptor antibodies for subacute encephalopathy; EEG for nonconvulsive status or fluctuating awareness; LP and imaging with focal signs, fever, headache or new seizure.
Trap
The classic trap is calling cognitive slowing pseudodementia in an older patient who actually has delirium or early dementia. Depression in the medically ill usually preserves orientation and effort; delirium fluctuates and impairs attention.
Rule of thumb
Ask what changed, when, and in what pattern. Acute and fluctuating means delirium; insidious and progressive with preserved attention means dementia; episodic and mood-congruent suggests a primary mood disorder.