It is assumed that all psychological and behavioural processes, whether normal or abnormal, are a result of normal or deranged brain function. A rational corollary would be that all psychiatric disorders are due to abnormal brain functioning and are therefore organic.However, this would be a gross oversimpliﬁcation.
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 psycho 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):
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:
Organic amnestic syndrome, and
Other organic mental disorders.
International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10)-WHO Version for ;2016
Mental and behavioural disorders
Organic, including symptomatic, mental disorders
This block comprises a range of mental disorders grouped together on the basis of their having in common a demonstrable etiology in cerebral disease, brain injury, or other insult leading to cerebral dysfunction. The dysfunction may be primary, as in diseases, injuries, and insults that affect the brain directly and selectively; or secondary, as in systemic diseases and disorders that attack the brain only as one of the multiple organs or systems of the body that are involved.
Dementia (F00-F03) is a syndrome due to disease of the brain, usually of a chronic or progressive nature, in which there is disturbance of multiple higher cortical functions, including memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement. Consciousness is not clouded. The impairments of cognitive function are commonly accompanied, and occasionally preceded, by deterioration in emotional control, social behaviour, or motivation. This syndrome occurs in Alzheimer disease, in cerebrovascular disease, and in other conditions primarily or secondarily affecting the brain.
Use additional code, if desired, to identify the underlying disease.
Alzheimer disease is a primary degenerative cerebral disease of unknown etiology with characteristic neuropathological and neurochemical features. The disorder is usually insidious in onset and develops slowly but steadily over a period of several years.
F00.0*Dementia in Alzheimer disease with early onset (G30.0†)
Dementia in Alzheimer disease with onset before the age of 65, with a relatively rapid deteriorating course and with marked multiple disorders of the higher cortical functions.
Alzheimer disease, type 2
Presenile dementia, Alzheimer type
Primary degenerative dementia of the Alzheimer type, presenile onset
F00.1*Dementia in Alzheimer disease with late onset (G30.1†)
Dementia in Alzheimer disease with onset after the age of 65, usually in the late 70s or thereafter, with a slow progression, and with memory impairment as the principal feature.
Alzheimer disease, type 1
Primary degenerative dementia of the Alzheimer type, senile onset
Senile dementia, Alzheimer type
F00.2*Dementia in Alzheimer disease, atypical or mixed type (G30.8†)
Atypical dementia, Alzheimer type
F00.9*Dementia in Alzheimer disease, unspecified (G30.9†)
Vascular dementia is the result of infarction of the brain due to vascular disease, including hypertensive cerebrovascular disease. The infarcts are usually small but cumulative in their effect. Onset is usually in later life.
F01.0Vascular dementia of acute onset
Usually develops rapidly after a succession of strokes from cerebrovascular thrombosis, embolism or haemorrhage. In rare cases, a single large infarction may be the cause.
Gradual in onset, following a number of transient ischaemic episodes which produce an accumulation of infarcts in the cerebral parenchyma.
Predominantly cortical dementia
F01.2Subcortical vascular dementia
Includes cases with a history of hypertension and foci of ischaemic destruction in the deep white matter of the cerebral hemispheres. The cerebral cortex is usually preserved and this contrasts with the clinical picture which may closely resemble that of dementia in Alzheimer disease.
F01.3Mixed cortical and subcortical vascular dementia
F01.8Other vascular dementia
F01.9Vascular dementia, unspecified
F02*Dementia in other diseases classified elsewhere
Cases of dementia due, or presumed to be due, to causes other than Alzheimer disease or cerebrovascular disease. Onset may be at any time in life, though rarely in old age.
A progressive dementia, commencing in middle age, characterized by early, slowly progressing changes of character and social deterioration, followed by impairment of intellect, memory, and language functions, with apathy, euphoria and, occasionally, extrapyramidal phenomena.
F02.1*Dementia in Creutzfeldt-Jakob disease (A81.0†)
A progressive dementia with extensive neurological signs, due to specific neuropathological changes that are presumed to be caused by a transmissible agent. Onset is usually in middle or later life, but may be at any adult age. The course is subacute, leading to death within one to two years.
A dementia occurring as part of a widespread degeneration of the brain. The disorder is transmitted by a single autosomal dominant gene. Symptoms typically emerge in the third and fourth decade. Progression is slow, leading to death usually within 10 to 15 years.
F04Organic amnesic syndrome, not induced by alcohol and other psychoactive substances
A syndrome of prominent impairment of recent and remote memory while immediate recall is preserved, with reduced ability to learn new material and disorientation in time. Confabulation may be a marked feature, but perception and other cognitive functions, including the intellect, are usually intact. The prognosis depends on the course of the underlying lesion.
F05Delirium, not induced by alcohol and other psychoactive substances
An etiologically nonspecific organic cerebral syndrome characterized by concurrent disturbances of consciousness and attention, perception, thinking, memory, psychomotor behaviour, emotion, and the sleep-wake schedule. The duration is variable and the degree of severity ranges from mild to very severe.
acute or subacute:
confusional state (nonalcoholic)
delirium tremens, alcohol-induced or unspecified (F10.4)
F05.0Delirium not superimposed on dementia, so described
F05.1Delirium superimposed on dementia
Conditions meeting the above criteria but developing in the course of a dementia (F00-F03).
Delirium of mixed origin
F06Other mental disorders due to brain damage and dysfunction and to physical disease
Includes miscellaneous conditions causally related to brain disorder due to primary cerebral disease, to systemic disease affecting the brain secondarily, to exogenous toxic substances or hormones, to endocrine disorders, or to other somatic illnesses.
resulting from use of alcohol and other psychoactive substances (F10-F19)
A disorder of persistent or recurrent hallucinations, usually visual or auditory, that occur in clear consciousness and may or may not be recognized by the subject as such. Delusional elaboration of the hallucinations may occur, but delusions do not dominate the clinical picture; insight may be preserved.
A disorder in which persistent or recurrent delusions dominate the clinical picture. The delusions may be accompanied by hallucinations. Some features suggestive of schizophrenia, such as bizarre hallucinations or thought disorder, may be present.
Paranoid and paranoid-hallucinatory organic states
Disorders characterized by a change in mood or affect, usually accompanied by a change in the overall level of activity, depressive, hypomanic, manic or bipolar (see F30-F38), but arising as a consequence of an organic disorder.
mood disorders, nonorganic or unspecified (F30-F39)
F06.4Organic anxiety disorder
A disorder characterized by the essential descriptive features of a generalized anxiety disorder (F41.1), a panic disorder (F41.0), or a combination of both, but arising as a consequence of an organic disorder.
anxiety disorders, nonorganic or unspecified (F41.-)
F06.5Organic dissociative disorder
A disorder characterized by a partial or complete loss of the normal integration between memories of the past, awareness of identity and immediate sensations, and control of bodily movements (see F44.-), but arising as a consequence of an organic disorder.
dissociative [conversion] disorders, nonorganic or unspecified (F44.-)
A disorder characterized by emotional incontinence or lability, fatigability, and a variety of unpleasant physical sensations (e.g. dizziness) and pains, but arising as a consequence of an organic disorder.
somatoform disorders, nonorganic or unspecified (F45.-)
F06.7Mild cognitive disorder
A disorder characterized by impairment of memory, learning difficulties, and reduced ability to concentrate on a task for more than brief periods. There is often a marked feeling of mental fatigue when mental tasks are attempted, and new learning is found to be subjectively difficult even when objectively successful. None of these symptoms is so severe that a diagnosis of either dementia (F00-F03) or delirium (F05.-) can be made. This diagnosis should be made only in association with a specified physical disorder, and should not be made in the presence of any of the mental or behavioural disorders classified to F10-F99. The disorder may precede, accompany, or follow a wide variety of infections and physical disorders, both cerebral and systemic, but direct evidence of cerebral involvement is not necessarily present. It can be differentiated from postencephalitic syndrome (F07.1) and postconcussional syndrome (F07.2) by its different etiology, more restricted range of generally milder symptoms, and usually shorter duration.
F06.8Other specified mental disorders due to brain damage and dysfunction and to physical disease
Epileptic psychosis NOS
F06.9Unspecified mental disorder due to brain damage and dysfunction and to physical disease
brain syndrome NOS
mental disorder NOS
F07Personality and behavioural disorders due to brain disease, damage and dysfunction
Alteration of personality and behaviour can be a residual or concomitant disorder of brain disease, damage or dysfunction.
F07.0Organic personality disorder
A disorder characterized by a significant alteration of the habitual patterns of behaviour displayed by the subject premorbidly, involving the expression of emotions, needs and impulses. Impairment of cognitive and thought functions, and altered sexuality may also be part of the clinical picture.
Residual nonspecific and variable behavioural change following recovery from either viral or bacterial encephalitis. The principal difference between this disorder and the organic personality disorders is that it is reversible.
A syndrome that occurs following head trauma (usually sufficiently severe to result in loss of consciousness) and includes a number of disparate symptoms such as headache, dizziness, fatigue, irritability, difficulty in concentration and performing mental tasks, impairment of memory, insomnia, and reduced tolerance to stress, emotional excitement, or alcohol.
Dementia Dementia is a chronic organic mental disorder, characterised by the following main clinical features: Impairment of intellectual functions, Impairment of memory (predominantly of recent memory,…