Violent Behavior: Causes and What to Do

When violent behavior has a medical cause

New aggression in someone who was previously calm suggests a brain or body problem. These causes are treatable, and recognizing them matters.

Delirium

Delirium is sudden confusion caused by illness. It can make people frightened, agitated and combative. Common triggers in older adults are urinary or chest infections, dehydration, constipation, pain, low oxygen, new medicines (especially sedatives, opioids and anticholinergics) and surgery. Delirium fluctuates through the day and is often worse at night.

Intoxication and withdrawal

• Alcohol is involved in a large share of violent incidents.
• Stimulants: methamphetamine, cocaine and some synthetic drugs cause paranoia and aggression.
• Anabolic steroids can increase irritability.
• Withdrawal from alcohol or sedatives can cause agitation, hallucinations and delirium tremens, a medical emergency.

Metabolic and neurological causes

• low blood sugar, particularly in people with diabetes
• low oxygen and very high or low sodium
• seizures, especially confusion after a seizure
• traumatic brain injury, particularly damage to the frontal lobes, which control impulses
• brain tumors, stroke, encephalitis and thyroid storm

Dementia

People with dementia may hit, push or shout when confused, frightened, in pain, overwhelmed or misunderstanding care such as washing. Aggression in frontotemporal dementia can appear early, with loss of social inhibition. A sudden change in a person with dementia usually means delirium.

Mental health conditions linked to aggression

• Intermittent explosive disorder: repeated outbursts of rage out of proportion to the trigger, followed by regret.
• Psychosis and schizophrenia: violence is uncommon but more likely when paranoid beliefs, command hallucinations or substance use are present and the illness is untreated.
• Mania in bipolar disorder: irritability and impulsiveness.
• PTSD: hyperarousal and anger, sometimes reacting to perceived threats.
• Personality disorders: antisocial and borderline personality disorder.
• Conduct disorder and oppositional defiant disorder in children and teens.
• Autism and intellectual disability: aggression is often a sign of distress, pain, sensory overload or difficulty communicating.

The strongest predictors of violence are past violence, substance use, young age, male sex and exposure to violence, rather than mental illness alone. People with mental illness are more often victims of violence than perpetrators.

Violent behavior in children

Tantrums with hitting are common in toddlers. Concern rises when aggression is frequent, severe, planned, involves weapons or cruelty to animals, or continues past early school years. Causes include ADHD, learning or language problems, autism, anxiety, trauma, exposure to violence at home and conduct disorder. Early parent training programs and therapy are effective.

How doctors assess violent behavior

The first step is safety for everyone, including the person. Then a clinician will:

• take a history from the person and family: timing, triggers, substance use, medicines, head injury, past violence
• check vital signs, blood sugar and oxygen
• examine for infection, injury or neurological signs
• order blood and urine tests (infection, electrolytes, kidney and liver function, drug screen) and sometimes a brain scan or EEG
• carry out a mental health assessment, including risk to self and others

Treatment and management

• Treat medical causes: infection, low blood sugar, withdrawal and medicine side effects.
• De-escalation: a calm voice, space, not arguing, reducing noise and offering choices. Restraint is a last resort.
• Psychological therapy: cognitive behavioral therapy, anger management and trauma-focused therapy.
• Medicines: for underlying conditions such as psychosis, mania or ADHD. Some medicines reduce aggression in specific conditions. In dementia, non-drug approaches come first because antipsychotics carry risks.
• Substance use treatment.
• Support for families and caregivers, including safety planning and respite.

Staying safe around someone who is aggressive

• Keep a safe distance and stay near an exit.
• Speak slowly and calmly; do not shout or make threats.
• Do not try to restrain the person.
• Remove weapons and items that could be thrown, if safe to do so.
• If danger is immediate, leave and call 911 or your local emergency number. Tell the dispatcher about any mental health condition so responders can prepare.

Frequently asked questions

What causes sudden violent behavior?

Sudden violence in someone who was previously calm is often due to a medical problem: delirium from infection or medicines, intoxication or withdrawal, low blood sugar, a head injury or seizure. Psychosis and mania are other causes. Sudden change needs urgent medical assessment.

Why is an elderly person suddenly aggressive?

In older adults, sudden aggression is most often delirium triggered by infection, dehydration, pain, constipation or a new medicine. In someone with dementia, it may also reflect fear, confusion or unmet needs. A same-day medical review is important.

Can a head injury cause violent behavior?

Yes. Traumatic brain injury, especially to the frontal lobes, can cause irritability, poor impulse control and aggressive outbursts. These can appear soon after the injury or develop over time. Rehabilitation, therapy and some medicines can help.

Is violent behavior a mental illness?

Violence itself is not a mental illness. It can be a symptom of some conditions, such as intermittent explosive disorder, psychosis or mania, but most people with mental illness are never violent. Substance use and past violence are stronger risk factors.

How do you calm a violent person?

Stay calm, keep a safe distance, speak slowly and quietly, avoid arguing and give the person space and simple choices. Do not try to restrain them. If anyone is at risk, leave and call 911 or your local emergency number.