This is a UKMLA-centred history guide about behaviour/personality change.

Introduction

Change in a person’s behaviour or personality can be categorised as Organic (i.e. underlying biological disease) or Non-Organic, such as personality disorders, bipolar disorder, depression, stress, etc. Organic causes can be further divided into primary (e.g. neurological) or secondary (e.g. from medications).

The affected individual may not be aware, therefore obtaining a collateral history is vital as it can help identify the specific behavioural issue (e.g. impulsive, sexual, anti-social, etc).

Common Causes of Behaviour/Personality Change

Presenting Complaint

Onset

• Hours → Recreational drug use (e.g. cocaine), Delirium
• Days → Drug induced (e.g. anti-seizure medication like levetiracetam), BPD
• Weeks/Months → Brain injury, Brain tumours, Alcohol misuse, Hydrocephalus, Depression, PTSD, Schizophrenia
• Years → Neurodegeneration (e.g. Parkinson’s disease, Frontotemporal dementia)
• Post-trauma (e.g. abuse, road traffic accident) → acute stress reaction (if symptoms occur <1 month after exposure to trauma) or PTSD (if symptoms occur >1 month after exposure to trauma)

Character

• Sexual/gambling/inappropriate behaviour, progressive → Frontotemporal dementia, bipolar disorder
• Depression, aggressive behaviour, confusion, progressive → Alzheimer’s dementia
• Progressive change in behaviour → Brain tumour
• Anti-social/inappropriate behaviour, non-progressive → Alcohol misuse, Drug abuse
• Age-inappropriate behaviour, not drug-induced or explained by social or cultural factors → consider personality disorders, trauma, and safeguarding issues in children/teenagers
• Flashbacks, nightmares, avoidance (of people or situation), hypervigilant, emotional numbing → PTSD
• Low mood, anergia (lack of energy to perform daily function) and anhedonia (loss of interest in activities previously enjoyed by patient) → Depression
• Odd, eccentric behaviour (e.g. paranoia, preferring solitary activities, behaving emotionless, strange beliefs) → Cluster A personality disorders (e.g. paranoid, schizoid or schizotypal)
• Dramatic, highly emotional, attention seeking, grandiosity, impulsive → Cluster B personality disorders (e.g. borderline, histrionic, narcissistic and antisocial)
• Anxious, fearful and worried behaviour → Cluster C personality disorders (e.g. obsessive-compulsive personality disorder, avoidant personality disorder and dependent personality disorder)
• Abnormally elevated mood, pressured speech, flight of ideas, grandiose delusions → manic episode of bipolar disorder
• Delusions, hallucinations, disorganised speech → psychosis
  • If associated with mood disturbance → depression, bipolar disorder, schizoaffective disorder

Associated Symptoms

• Fever, seizures, confusion, photophobia → viral/bacterial encephalitis
  • If seizures are absent → consider meningitis
• Worsening headache → hydrocephalus, brain tumour
• Rapid eye movement sleep behaviour disorder (e.g. acting out dreams), visual hallucination (e.g. lilliputian) → Lewy body dementia
• Memory loss, visual agnosia → Alzheimer’s dementia
• Weight loss, loss of appetite, change in bowel habits → malignancy
• Sleep problems, difficulty concentrating, persistent negative emotional state → depression, PTSD
• Psychosis with absent mood disorders (e.g. depression) → schizophrenia

Red Flags

• Fever, confusion, acute change in cognition → infectious encephalitis
• Night sweats, fever, weight loss → Tuberculous encephalopathy or CNS lymphoma
• Signs of raised intracranial pressure e.g. headache worse on coughing → brain tumour, brain bleed, hydrocephalus
• Progressive worsening headache → brain tumour, intracranial bleed, hydrocephalus
• FLAWS symptoms → malignancy

Background

Past Medical History

• Head trauma or stroke → brain injury
• Malignancy (e.g. prostate cancer, breast cancer) → brain metastases
• Depression, cognitive impairment in an elderly person (>65 years) → dementia
• Arteriovenous (AV) malformation → obstructive hydrocephalus
• Spina bifida/neural tube defects → congenital hydrocephalus
• Epilepsy → antiseizure medications
• HIV → immunodeficiency causes CNS lymphoma

Family History

• Frontotemporal dementia has a strong familial component
• Neurofibromatosis can increase the risk of brain tumours
• Primary brain tumours in first-degree family members
• Hereditary haemorrhagic telangiectasia increases the risk of AV malformations
• Schizophrenia has a strong familial component

Social History

• Recreational drug use (e.g cocaine, amphetamines or alcohol abuse)
• Multiple sexual partners → HIV-associated CNS lymphoma
• History of abuse, traumatic event → depression, PTSD

Common OSCE Histories

Examining Change in Personality or Behaviour

When examining a person with behavioural change, a cranial and peripheral nerve exam is important to perform, in order to identify any focal neurological deficits.

Look for signs of space-occupying the lesion:

• Surgical oculomotor nerve palsy (dilated, unreactive pupil)
• Abducens nerve palsy
• Hemiparesis (note weakness is more common if frontal lobes are affected)
• Upper motor neuron signs

Doing a mental status examination and cognitive assessments (especially in elderly patients) are equally important as they can guide you towards a psychiatric diagnosis or dementia, respectively. Remember, common things are common!

If you are unsure, be honest and tell the examiner of your key findings and how you will confirm the possible aetiology (e.g. MRI head, urine toxicology)

References
 
1. https://www.rcemlearning.co.uk/reference/acute-behavioural-disturbance/#1639499533066-71ae3a3b-43c2 [Accessed 15/7/24]

2. https://www.msdmanuals.com/en-gb/home/mental-health-disorders/overview-of-mental-health-care/personality-and-behavior-changes#Evaluation_v1665589 [Accessed 15/7/24]

3. https://patient.info/doctor/personality-disorders-and-psychopathy [Accessed 15/7/24]

Author – Dr Karthikeyan Sivaganesh   

Editor – Dr James Mackintosh

Last updated 24/01/2026