ADHD: What Causes It

Risk Factors

Scientists are not sure what causes ADHD. Like many other illnesses, a number of factors can contribute to ADHD, such as:

  • Genes
  • Cigarette smoking, alcohol use, or drug use during pregnancy
  • Exposure to environmental toxins during pregnancy
  • Exposure to environmental toxins, such as high levels of lead, at a young age
  • Low birth weight
  • Brain injuries

ADHD is more common in males than females, and females with ADHD are more likely to have problems primarily with inattention. Other conditions, such as learning disabilities, anxiety disorder, conduct disorder, depression, and substance abuse, are common in people with ADHD.