Aggression: Causes and What to Do

What counts as aggression?

Aggression includes:

• Verbal: shouting, insults, threats, intimidation.
• Physical: hitting, kicking, biting, pushing, throwing or breaking things, self-harm.
• Reactive (impulsive): a sudden "hot" response to frustration or a perceived threat.
• Proactive (instrumental): planned aggression to get something or dominate others.

Anger is an emotion. Aggression is a behavior. Most people feel anger without acting aggressively. Aggression becomes a concern when it is frequent, intense, out of proportion to the trigger, or causes injury, legal problems or broken relationships. See also excessive anger and hostile behavior.

Aggression in children and teens

Toddlers commonly hit, bite and have tantrums, peaking around age 2 to 3, because they cannot yet express frustration in words or control impulses. This usually fades by school age as language and self-control develop.

Causes of persistent aggression in children:

• ADHD: impulsivity and low frustration tolerance lead to outbursts.
• Oppositional defiant disorder: frequent anger, arguing and defiance toward adults, for at least 6 months.
• Conduct disorder: a pattern of violating others' rights, such as cruelty to people or animals, fights, destruction or theft.
• Autism spectrum disorder: aggression often comes from sensory overload, communication difficulty or changes in routine.
• Anxiety, depression and trauma: irritable or aggressive behavior can be how children show distress.
• Learning and language problems: frustration at school.
• Home environment: exposure to violence, harsh or inconsistent discipline, bullying or abuse.

Aggression in adults

• Substance use: alcohol is the substance most strongly linked to violence. Stimulants, anabolic steroids and withdrawal from alcohol or sedatives can also trigger aggression.
• Intermittent explosive disorder: repeated, sudden outbursts of rage that are grossly out of proportion, followed by regret.
• Bipolar disorder: irritability and aggression during manic or mixed episodes.
• Post-traumatic stress disorder: hyperarousal, a hair-trigger temper and feeling constantly on guard.
• Depression: especially in men, irritability and anger can be prominent.
• Psychosis and schizophrenia: aggression is uncommon but more likely when paranoid beliefs or command hallucinations are present and untreated, particularly with substance use.
• Personality disorders: such as borderline or antisocial personality disorder.
• Chronic stress, pain and sleep deprivation lower tolerance for frustration.

Medical causes of sudden aggression

A sudden change in behavior, especially in someone who was previously calm, needs a medical check.

• Delirium: an acute confusional state from infection (such as a UTI or pneumonia), dehydration, medicines, surgery or alcohol withdrawal. Common in older adults.
• Traumatic brain injury: damage to the frontal lobes reduces impulse control. Aggression can appear weeks or months after injury.
• Low blood sugar: confusion, sweating, shakiness and irritability in people taking insulin or some diabetes tablets.
• Hyperthyroidism: irritability, anxiety and restlessness.
• Brain tumors, strokes, encephalitis and epilepsy (particularly around seizures).
• Medicines: steroids, levetiracetam, some sleeping pills and others can cause irritability or aggression.
• Severe pain in someone who cannot communicate it.

Aggression in older adults and dementia

In dementia, aggression often happens during personal care such as bathing or dressing, when the person feels threatened, confused, embarrassed or in pain. Common triggers include:

• pain, constipation, infection, hunger or needing the toilet
• noise, crowding or unfamiliar people and places
• feeling rushed or corrected
• hearing or vision loss causing misunderstanding
• tiredness later in the day ("sundowning")

A sudden worsening over hours or days is more likely to be delirium than progression of dementia.

How aggression is assessed

A doctor or mental health professional will ask about the pattern of outbursts, triggers, substance use, sleep, mood, head injuries, medicines and any risk to others. A physical examination and tests such as blood sugar, blood count, thyroid and kidney function, urine tests and drug screening look for medical causes. A brain scan is done when there are neurological signs or a recent injury. In children, school reports and developmental assessment are valuable.

What to do during an aggressive episode

• Keep yourself and others safe. Leave the room or keep a clear exit. Remove objects that could be used as weapons.
• Stay calm. Use a quiet, steady voice and short sentences. Do not argue, threaten or touch the person.
• Give space and avoid standing directly in front of them or blocking their way.
• Acknowledge feelings: "I can see you are really upset."
• Call for help if there is any risk of serious harm.

Treatment of aggression

Treatment targets the underlying cause:

• Medical causes: treating infection, correcting blood sugar, adjusting medicines.
• Psychological therapies: cognitive behavioral therapy, anger management programs and dialectical behavior therapy teach people to recognize early warning signs and respond differently.
• Parent training: parent management training is the most effective treatment for aggression in younger children with ODD or conduct problems.
• Substance use treatment for alcohol or drug problems.
• Medicines: treating ADHD, depression, bipolar disorder or psychosis often reduces aggression. Mood stabilizers or antipsychotics are sometimes prescribed for severe aggression, but carry side effects and are used cautiously, especially in dementia.
• Dementia care: identifying and removing triggers, treating pain, keeping routines and approaching care calmly. Non-drug strategies come first.

Frequently asked questions

What causes sudden aggression in adults?

Sudden aggression in an adult who was previously calm can come from alcohol or drugs, withdrawal, low blood sugar, delirium from infection, a head injury, a stroke, seizures or a medicine side effect. Mental health crises such as mania or psychosis are other causes. A sudden change needs medical assessment.

Is aggression a symptom of a mental illness?

It can be. Aggression occurs in ADHD, oppositional defiant and conduct disorders, intermittent explosive disorder, bipolar disorder, PTSD and some cases of psychosis. However, most people with mental illness are not violent, and many aggressive people have no mental illness. Substance use is a bigger factor.

Why is my elderly parent suddenly aggressive?

A sudden change over hours or days in an older person is often delirium, caused by an infection such as a UTI, dehydration, constipation, pain or a new medicine. In dementia, aggression often occurs during personal care. Contact their doctor promptly to look for a treatable cause.

Is aggression normal in toddlers?

Some hitting, biting and tantrums are normal around ages 2 to 3, as toddlers lack words to express frustration. It usually decreases by age 4 to 5. Aggression that is frequent, causes injuries, or continues into school age warrants a check with a pediatrician.

How can I manage my own aggression?

Notice early warning signs such as a racing heart, clenched jaw or rising voice. Step away, breathe slowly and return when calm. Reduce alcohol, sleep enough and exercise regularly. Anger management programs and cognitive behavioral therapy are effective if outbursts keep happening.