Types of Organic Mental Disorders:
According to our present knowledge, there are broadly three types of psychiatric disorders:
- Those due to a known organic cause.
- Those in whose causation an organic factor has not yet been found or proven.
- Those primarily due to unpredictable social factors.
Only disorders with a known organic cause are called organic mental disorders. Thus, organic mental
disorders are behavioural or psychological disorders associated with transient or permanent brain dysfunction and include only those mental and behavioural disorders that are due to demonstrable cerebral disease or disorder, either primary (primary brain pathology) or secondary (brain dysfunction due to systemic diseases). The use of term organic here does not imply that other psychiatric disorders are ‘non-organic’ in the sense of having no biological basis. It simply means that the organic mental disorders have a demonstrable and independently diagnosable cerebral disease or disorder, unlike other psychiatric disorders that do not at present.
Since organic brain illness can mimic any psychiatric disorder, especially in the initial stages, organic mental disorder should be the first consideration in evaluating a patient with any psychological or behavioural clinical syndrome. The presence of following features requires a high index of suspicion for an organic mental disorder (or what is loosely called as organicity):
- First episode.
- Sudden onset.
- Older age of onset.
- History of drug and/or alcohol use disorder.
- Concurrent medical or neurological illness.
- Neurological symptoms or signs, such as seizures, impairment of consciousness, head injury, sensory or motor disturbance.
- Presence of confusion, disorientation, memory impairment or soft neurological signs.
- Prominent visual or other non-auditory (e.g. olfactory, gustatory or tactile) hallucinations.
These disorders can be broadly sub-categorised into the following categories:
- Delirium,
- Dementia,
- Organic amnestic syndrome and
- Other organic mental disorders.