Organic Mental Disorders

These are mental or behavioral abnormalities resulting from a demonstrable, underlying brain disease, brain injury, or other physical (somatic) disease that directly affects brain function. Unlike “functional” psychiatric disorders where the primary issue is thought to be in brain function without gross structural damage easily identifiable, organic disorders have a clear, identifiable physical cause impacting the brain’s structure or physiology. The term “organic” is less commonly used in newer diagnostic classifications (like DSM-5 which prefers terms like “Neurocognitive Disorders” or “Mental Disorder Due to Another Medical Condition”), but the concept remains important.

Key Distinguishing Feature: The mental symptoms are a direct physiological consequence of a medical condition.

1. Delirium

• Core Feature: An acute disturbance in attention (reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment). The disturbance develops over a short period (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.

• Additional Features:

  • Disturbance in cognition (e.g., memory deficit, disorientation, language disturbance, visuospatial ability, or perception – including illusions or hallucinations).

  • The disturbances are a direct physiological consequence of another medical condition, substance intoxication or withdrawal, exposure to a toxin, or are due to multiple etiologies.

• Common Causes (Often multifactorial – “I WATCH DEATH” mnemonic can be helpful):

  • Infection (e.g., UTI, pneumonia, sepsis)

  • Withdrawal (alcohol, benzodiazepines)

  • Acute metabolic disturbance (e.g., electrolyte imbalance, hypoglycemia, hypoxia, liver/kidney failure)

  • Trauma (head injury, post-operative)

  • CNS pathology (e.g., stroke, tumor, seizures, meningitis, encephalitis)

  • Hypoxia (from any cause)

  • Deficiencies (e.g., thiamine, B12)

  • Endocrinopathies (e.g., thyroid, adrenal disorders)

  • Acute vascular (e.g., hypertensive encephalopathy, shock)

  • Toxins or drugs (medication side effects – especially anticholinergics, opioids; illicit drugs)

  • Heavy metals

• Presentation: Can be hyperactive (agitated, restless), hypoactive (lethargic, withdrawn – often missed), or mixed.

• Management: Identify and treat the underlying cause(s) urgently. Provide supportive care (hydration, nutrition, safe environment, reorientation). Manage agitation cautiously with medication if necessary. Delirium is a medical emergency.

2. Dementia (Now primarily termed Major Neurocognitive Disorder)

• Core Feature: Significant cognitive decline from a previous level of performance in one or more cognitive domains (e.g., complex attention, executive function, learning and memory, language, perceptual-motor, or social cognition). The cognitive deficits interfere with independence in everyday activities.

• Key Characteristics:

  • Insidious onset and progressive course (usually, but can vary depending on cause).

  • Not occurring exclusively during the course of a delirium.

  • Not better explained by another mental disorder.

• Common Types/Causes:

  • Alzheimer’s Disease: Most common cause. Characterized by amyloid plaques and neurofibrillary tangles in the brain. Typically insidious onset and gradual progression, with memory impairment often an early and prominent feature.

  • Vascular Dementia (Vascular Neurocognitive Disorder): Caused by cerebrovascular disease (e.g., multiple strokes or small vessel disease). Onset can be sudden or stepwise. Cognitive deficits are often related to the location of vascular damage.

  • Dementia with Lewy Bodies (Neurocognitive Disorder with Lewy Bodies): Characterized by Lewy bodies (abnormal protein deposits) in the brain. Core features include fluctuating cognition with pronounced variations in attention and alertness, recurrent visual hallucinations (often well-formed and detailed), and spontaneous features of parkinsonism.

  • Frontotemporal Dementia (Frontotemporal Neurocognitive Disorder): A group of disorders characterized by degeneration of the frontal and/or temporal lobes. Can present with behavioral changes (e.g., disinhibition, apathy, compulsivity – behavioral variant FTD) or language difficulties (primary progressive aphasia).

  • Parkinson’s Disease Dementia (Neurocognitive Disorder due to Parkinson’s Disease): Dementia develops in the context of established Parkinson’s disease, typically many years after motor symptoms begin.

  • Traumatic Brain Injury (TBI)-Related Dementia.

  • Substance/Medication-Induced Neurocognitive Disorder.

  • HIV Infection-Related Dementia.

  • Huntington’s Disease-Related Dementia.

  • Prion Disease (e.g., Creutzfeldt-Jakob disease)-Related Dementia.

• Management: Depends on the underlying cause. Some causes are potentially reversible (e.g., if due to vitamin deficiency or thyroid disorder, though these are less common causes of major NCD). For progressive dementias like Alzheimer’s:

  • Medications to manage cognitive symptoms (e.g., cholinesterase inhibitors, memantine).

  • Management of behavioral and psychological symptoms (BPSD) (e.g., agitation, depression, psychosis) with non-pharmacological approaches first, then medication if necessary.

  • Supportive care for the individual and caregivers (education, respite care, safety planning).

3. Amnestic Disorders (Now primarily termed Major or Mild Neurocognitive Disorder, often specifying the etiological subtype or “due to another medical condition”)

• Core Feature: A significant impairment in memory (inability to learn new information or recall previously learned information) that is not due to delirium or dementia and represents a significant decline from a previous level of functioning.

• Key Characteristics:

  • Memory impairment is the predominant symptom.

  • No significant impairment in other cognitive functions (like language, executive function) that would meet criteria for dementia.

• Common Causes:

  • Thiamine deficiency (Wernicke-Korsakoff syndrome, often related to chronic alcohol abuse).

  • Head trauma.

  • Hypoxia or anoxia (e.g., after cardiac arrest).

  • Stroke affecting specific memory-related brain areas (e.g., thalamus, hippocampus).

  • Herpes simplex encephalitis.

  • Brain surgery involving temporal lobes.

• Management: Treat the underlying cause if possible. Cognitive rehabilitation and compensatory strategies (e.g., memory aids). Supportive care.

4. Mental Disorders Due to Another Medical Condition
This is a broad category where symptoms characteristic of a specific mental disorder (e.g., depressive disorder, anxiety disorder, psychotic disorder, personality change) are judged to be the direct physiological consequence of a general medical condition.

• Diagnosis Requires:

  • Evidence from history, physical examination, or laboratory findings that the disturbance is the direct pathophysiological consequence of another medical condition.

  • The disturbance is not better explained by another mental disorder.

  • The disturbance does not occur exclusively during the course of a delirium.

  • The disturbance causes clinically significant distress or impairment.

• Examples:

  • Psychotic Disorder Due to Another Medical Condition: (e.g., psychosis due to Cushing’s disease, brain tumor, or epilepsy).

  • Depressive Disorder Due to Another Medical Condition: (e.g., depression due to hypothyroidism, stroke, Parkinson’s disease, or pancreatic cancer).

  • Anxiety Disorder Due to Another Medical Condition: (e.g., anxiety due to hyperthyroidism, pheochromocytoma, or hypoglycemia).

  • Personality Change Due to Another Medical Condition: (e.g., persistent personality disturbance after a traumatic brain injury).

• Management: Primarily involves treating the underlying medical condition. Symptomatic treatment for the mental health symptoms may also be necessary (e.g., antidepressants for depression due to hypothyroidism, alongside thyroid hormone replacement).

Key Considerations in Organic Mental Disorders:

• Thorough Medical Evaluation: Essential to identify the underlying physical cause. This includes a detailed history, physical examination (including neurological exam), laboratory tests, and often neuroimaging.

• Temporal Relationship: The onset of mental symptoms is often closely related in time to the onset or exacerbation of the medical condition.

• Atypical Presentation: Mental symptoms may present atypically compared to primary “functional” psychiatric disorders (e.g., late age of onset for a first psychotic episode should raise suspicion of an organic cause).

• Reversibility: Some organic mental disorders are reversible if the underlying cause is treated promptly and effectively (e.g., delirium due to UTI, amnesia due to thiamine deficiency if treated early). Others, like most dementias, are progressive.

• Treatment Focus: Addressing the underlying medical condition is paramount. Symptomatic psychiatric treatment is often adjunctive.

• Supportive Care: Maintaining safety, nutrition, hydration, and providing support to the individual and their family/caregivers is crucial.

Understanding the distinction and overlap between organic and functional mental disorders is vital for accurate diagnosis, appropriate treatment planning, and providing holistic care.