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Fixed abnormal beliefs

Specialties > Mental health

Differential Diagnosis Schema 🧠

Psychotic Disorders

  • Schizophrenia: Characterized by delusions, hallucinations, disorganized speech, and negative symptoms such as blunted affect or social withdrawal.
  • Schizoaffective Disorder: Features of both schizophrenia and mood disorder (either bipolar or depressive type); includes persistent delusions.
  • Delusional Disorder: Presence of one or more delusions for at least one month, without other prominent symptoms of schizophrenia.
  • Brief Psychotic Disorder: Sudden onset of psychotic symptoms, including delusions, lasting more than a day but less than a month.
  • Psychotic Depression: Severe depressive episode with psychotic features, including delusions congruent with mood (e.g., guilt, poverty, illness).
  • Bipolar Disorder with Psychotic Features: Delusions or hallucinations occurring during manic or depressive episodes.
  • Substance-Induced Psychotic Disorder: Psychosis due to intoxication or withdrawal from substances like alcohol, cannabis, or stimulants.
  • Paranoid Personality Disorder: Pervasive distrust and suspicion of others, with beliefs that are not of delusional intensity.

Neurocognitive Disorders

  • Dementia (e.g., Alzheimer’s Disease): Delusions are common, particularly in the later stages, often involving themes of persecution or infidelity.
  • Delirium: Acute confusional state with fluctuating consciousness, inattention, and delusions, often secondary to a medical condition or substance.
  • Lewy Body Dementia: Characterized by visual hallucinations, parkinsonism, and fluctuating cognitive impairment, often with delusional thoughts.
  • Frontal Lobe Disorders: Frontal lobe damage or tumors may present with personality changes, disinhibition, and delusional beliefs.
  • Huntington’s Disease: Neurodegenerative disorder with psychiatric symptoms, including delusions, as well as movement abnormalities.

Mood Disorders with Psychotic Features

  • Major Depressive Disorder with Psychotic Features: Severe depression with mood-congruent delusions (e.g., guilt, poverty, illness).
  • Bipolar Disorder: During manic or depressive episodes, delusions may occur, often congruent with the patient’s mood (e.g., grandiosity in mania).
  • Postpartum Psychosis: Severe psychiatric condition following childbirth, often involving delusions, confusion, and mood instability.

Medical and Substance-Related Causes

  • Substance-Induced Psychosis: Delusions or hallucinations caused by substances such as alcohol, cannabis, amphetamines, or hallucinogens.
  • Medication-Induced Psychosis: Psychotic symptoms can be a side effect of certain medications, including corticosteroids and anticholinergics.
  • Infections: CNS infections such as encephalitis, HIV, or neurosyphilis can present with delusions.
  • Endocrine Disorders: Conditions such as hyperthyroidism or Cushing’s syndrome can cause psychiatric symptoms, including delusions.
  • Autoimmune Encephalitis: Associated with psychiatric symptoms including delusions, particularly in young adults.
  • Paraneoplastic Syndromes: Certain cancers, particularly small-cell lung cancer, can cause psychiatric symptoms including delusions.
  • Metabolic Disturbances: Electrolyte imbalances, liver or kidney failure can lead to delirium and delusions.
  • Sleep Deprivation: Prolonged lack of sleep can lead to psychotic symptoms, including fixed delusions.
  • Heavy Metal Poisoning: Exposure to lead, mercury, or other heavy metals can cause neuropsychiatric symptoms including delusions.

Key Points in History 🥼

Nature of the Beliefs

  • Content of Delusions: Determine the theme of the delusion (e.g., persecutory, grandiose, somatic, nihilistic) and how it impacts the patient’s life.
  • Onset and Duration: When did the abnormal beliefs begin, and how have they evolved over time? Sudden onset might suggest delirium or substance use.
  • Insight: Assess the patient’s level of insight into their beliefs. Do they recognize them as possibly irrational, or are they fully convinced?
  • Impact on Functioning: Evaluate how the beliefs affect daily activities, relationships, and occupational functioning.
  • Associated Symptoms: Inquire about hallucinations, disorganized thinking, or mood symptoms that may accompany the delusions.
  • Risk Assessment: Consider any risk to the patient or others due to their delusions, particularly if the beliefs involve persecution or command hallucinations.
  • Response to Previous Treatment: If the patient has a history of similar episodes, what treatments were effective, and how did the beliefs change?
  • Triggers: Explore any potential triggers such as stress, substance use, or medical conditions that could have precipitated the onset of delusions.

Background

  • Past Psychiatric History: Previous episodes of psychosis, mood disorders, or substance use disorders are relevant.
  • Medical History: Review any history of neurological disorders, infections, or endocrine abnormalities.
  • Drug History: Consider current and past medications, as well as any use of recreational drugs or alcohol that could contribute to psychosis.
  • Family History: Ask about family history of psychiatric disorders, particularly schizophrenia, bipolar disorder, or depression with psychotic features.
  • Social History: Evaluate the patient’s social circumstances, including stressors, support systems, and any recent life changes.
  • Cognitive Function: Assess for any cognitive deficits that may indicate underlying dementia or other neurocognitive disorders.
  • Developmental History: Consider in younger patients or those with a history of learning difficulties or developmental delay.
  • Cultural and Religious Context: Some beliefs may be influenced by cultural or religious background; understanding this context is crucial for accurate diagnosis.

Possible Investigations 🌡️

Blood Tests

  • Full Blood Count (FBC): To assess for infection, anemia, or other underlying conditions that might contribute to delirium.
  • Urea and Electrolytes (U&E): To detect electrolyte imbalances that can affect mental status.
  • Liver Function Tests (LFTs): To assess for hepatic encephalopathy, particularly in patients with known liver disease.
  • Thyroid Function Tests: To rule out hypo- or hyperthyroidism as a cause of psychiatric symptoms.
  • Vitamin B12 and Folate Levels: Deficiencies in these vitamins can contribute to cognitive decline and psychiatric symptoms.
  • Blood Glucose: Hypoglycemia can cause acute confusion or delirium, presenting with abnormal beliefs.
  • Toxicology Screen: Important in cases where substance misuse is suspected.
  • Autoimmune and Infectious Screening: Consider autoantibody tests and screening for infections like HIV, syphilis, and Lyme disease in cases of new-onset psychosis.
  • Calcium and Magnesium Levels: Electrolyte disturbances can contribute to psychiatric symptoms.
  • ESR/CRP: To assess for underlying inflammatory or autoimmune conditions.
  • Cortisol Levels: Consider in cases where Cushing’s syndrome is a potential cause of psychiatric symptoms.
  • Heavy Metal Screening: Useful in cases where environmental exposure to toxins like lead or mercury is suspected.
  • Paraneoplastic Antibody Screening: Consider in patients with risk factors for malignancy presenting with new-onset psychosis.

Imaging and Other Tests

  • CT/MRI Brain: To assess for structural brain abnormalities, tumors, or evidence of cerebrovascular disease that could contribute to delusions.
  • EEG (Electroencephalogram): Useful in assessing for epilepsy or encephalopathy, particularly in cases of fluctuating consciousness or confusion.
  • Lumbar Puncture: Indicated if CNS infection or inflammation (e.g., encephalitis, meningitis) is suspected.
  • Neuropsychological Testing: Helps assess cognitive function in cases where dementia or another neurocognitive disorder is suspected.
  • Chest X-ray/CT: Consider in cases where a paraneoplastic syndrome or infection such as tuberculosis is suspected.
  • PET Scan: Occasionally used in complex cases to assess metabolic activity in the brain, particularly in neurodegenerative conditions.
  • Sleep Study: Consider in cases where sleep disorders such as obstructive sleep apnea could be contributing to psychiatric symptoms.
  • ECG and Cardiac Monitoring: Consider if syncope or cardiac arrhythmias could be contributing to episodes of confusion or abnormal beliefs.

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Mental health