Organic Mental Disorders: Delirium, Dementia, and Amnestic Syndrome

1. Overview & Epidemiology

The unifying concept of an organic mental disorder (examiner favourite, from PSY 4.116):

There is a causal relationship between the organic (somatic) disease and the psychopathology.
The somatic pathology precedes the psychiatric symptoms.
The course of the physical illness and the mental disorder run in parallel.
A heteroanamnesis (collateral history from family/carers) is fundamental — alongside differential-diagnostic tests, not optional.

Definition (Debrecen): a disturbance of integration of consciousness with an organic background, involving disorientation, hallucinations, psychomotor excitement, and vegetative (autonomic) symptoms. Amentia is essentially the same picture without the vegetative symptoms.
Hallmark: acute, clouded/fluctuating consciousness with impaired attention. Often reversible once the cause is treated.
Epidemiology: common in hospitalised and elderly patients; risk rises with age and number of medications.

Definition (Debrecen): marked by severe impairment of memory, judgement, orientation, and cognition, with motor dysfunction appearing late. Consciousness is clear (in contrast to delirium).
Epidemiology (PSY 1.1):
- ~10% of people over 65 (10% prevalence over 65 also quoted for AD in Hungary).
- 30–50% of people over 85.
- Frequency increases with age (it does NOT decrease — the classic trap).
Relative frequencies of subtypes:
- Alzheimer's disease (AD): 50–60% of all dementias (Debrecen: 60–70% of all dementias).

Definition: an isolated, prominent memory impairment with preserved consciousness, attention and other cognitive domains — distinguishing it from both delirium (consciousness clouded) and dementia (global decline).
Core cause: vitamin B1 (thiamine) deficiency is fundamental in Korsakoff syndrome (PSY 4.115, 4.121.4) — most often from chronic alcohol intake. Other causes: head trauma, atherosclerotic change, intoxication, CO poisoning.