What causes aggression?

Although specific causes of aggression are not known, some studies have shown that abnormal brain chemistry or structural changes may play a role. Environment and genetics also seem to be involved. Aggression is a potential symptom of diseases, disorders or conditions that interfere with thought processes, such as dementia, post-traumatic stress disorder, schizophrenia, and a number of personality disorders.

Psychiatric and cognitive causes of aggression

Aggression may be caused by psychiatric or cognitive diseases, disorders or conditions including:

  • Antisocial personality disorder (disordered perceptions and interactions with others)
  • Attention-deficit hyperactivity disorder (ADHD)
  • Autism
  • Borderline personality disorder (disorder characterized by unstable relationships)
  • Conduct disorder (behavior disorder of childhood)
  • Dementia, including Alzheimer’s disease and Huntington’s disease
  • Intermittent explosive disorder (disorder characterized by extreme anger)
  • Oppositional defiant disorder (pattern of defiance and hostile behavior toward authority figures)
  • Post-traumatic stress disorder
  • Schizophrenia
  • Substance abuse

Other causes of aggression

Aggression can also be caused by other diseases, disorders or conditions including:

  • Brain tumors
  • Head injury

Serious or life-threatening causes of aggression

In some cases, aggression may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

  • Acute delirium (sudden onset of mental status changes due to illness or toxicity)
  • Alcohol or drug intoxication or withdrawal
  • Hypoglycemia (low blood sugar)
  • Mania (elevated mood and energy levels that can occur in bipolar disorder)
  • Meningitis (infection or inflammation of the sac around the brain and spinal cord)
  • Stroke
  • Traumatic brain injury

Questions for diagnosing the cause of aggression

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your aggression including:

  • When did you first notice your aggression?
  • What do you find provokes your aggression?
  • Where do you direct your aggression?
  • What kind of aggressive behaviors have you noticed?
  • Do you have any other symptoms?
  • Do you have a family history of mental illness?
  • Do you have any other psychiatric or medical problems?
  • What medications are you taking?
  • Are you taking other drugs?
  • Do you use alcohol?

What are the potential complications of aggression?

Because aggression can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Difficulties at work, in school, in social environments, and with relationships
  • Drug and alcohol use and abuse
  • Drug overdose or alcohol poisoning
  • Increased risk of injury
  • Law violations and legal troubles
  • Self-harm
  • Suicide or violence


  1. Drug abuse and addiction: One of America’s most challenging public health problems. National Institute on Drug Abuse. http://archives.drugabuse.gov/about/welcome/aboutdrugabuse/.
  2. Dementia. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001748/.
  3. Siever LJ. Neurobiology of aggression and violence. Am J Psychiatry 2008; 165:429.


What is aggression?

Aggression is a behavior characterized by strong self-assertion with hostile or harmful tones. Under some circumstances, aggression may be a normal reaction to a threat. Alternatively, it may be abnormal, unprovoked or reactive behavior (intermittent explosive disorder). Anger, confusion, discomfort, fear, overstimulation and tiredness can lead to aggressive reactions.

Aggres... Read more about aggressionintroduction


What other symptoms might occur with aggression?

Aggression may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Conditions that frequently affect behavior may also have other psychological, cognitive or physical symptoms.

Psychological and cognitive symptoms that may occur along with aggression

Aggression may accompany other psychological or cognitive symptoms including:<... Read more about aggressionsymptoms

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Aug 9, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Mental Health and Behavior