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ADHD Symptoms, Complications and Causes

You’ll find that a lot of the symptoms of attention deficit hyperactivity disorder, such as struggling to pay attention, acting impulsively or finding it hard to sit still, appear in many children and adults. But people who have ADHD may experience them more frequently and more intensely. Symptoms affect their performance, relationships, or social interactions.

Many behaviors associated with ADHD are typical for younger children, but in most children, they improve with age. They are not signs of defiance or an inability to understand directions. ADHD symptoms can make children lag in development compared to their peers.

Symptoms of ADHD

If you or a loved one has ADHD, you might notice difficulty in these areas.


  • Paying attention or sustaining an attention span when they aren’t interested in the topic
  • Daydreaming
  • Seeming not to listen
  • Losing focus during lectures, conversations or reading
  • Completing tasks that require sustained effort
  • Forgetfulness or losing things such as school supplies, keys or cell phones
  • Missing due dates, deadlines or meetings
  • Poor time management
  • Becoming easily distracted
  • Making careless mistakes
  • Staying on task
  • Meeting deadlines
  • Work or school performance


  • Taking risks without considering the consequences
  • Difficulty controlling impulses
  • Fidgeting, squirming or other symptoms of hyperactivity
  • Poor frustration tolerance
  • Anger outbursts


  • Waiting in line or having difficulty waiting in other situations, such as taking turns
  • Talking excessively or out of turn
  • Answering questions before the other person finishes asking
  • Finishing other people’s sentences

Symptoms of ADHD can be mild or severe and can shift as a person ages. Often, young children mainly exhibit hyperactivity and impulsive behavior. Inattention can be a bigger factor in elementary school years. In adolescence, symptoms can shift to restlessness, fidgeting, relationship problems and antisocial behaviors. Adults often notice inattention, restlessness and impulsivity.

Complications of ADHD

Living with ADHD can be a challenge, and if you have the condition, you could be more likely to experience:

  • Trouble keeping up with work or school assignments
  • Difficulty holding a job
  • Poor physical and mental health
  • Problems managing money
  • Trouble with law enforcement
  • Poor self-image
  • Substance or alcohol misuse or abuse
  • Frequent accidents
  • Difficulty maintaining relationships

Other conditions you may see along with ADHD

Sometimes people who have ADHD also have other mental health conditions:

  • Oppositional defiant disorder or behavior in children and adolescents
  • Mood disorders such as depression or bipolar disorders
  • Anxiety disorders
  • Substance use disorders
  • Learning disabilities

What are the causes of ADHD?

According to the National Institute of Mental Health, experts don’t know exactly what causes ADHD. However, genetic factors seem to play a role, and some genes are linked to the disorder. You’re also at higher risk for ADHD if you have a parent or sibling with ADHD or other mental health disorders.

ADHD probably stems from a combination of risk factors. More research is needed to see if environmental factors, environmental toxins, brain injury, nutrition or social settings contribute to developing ADHD. It’s not caused by eating sugar, poor parenting or too much screen time.

Brain imaging has shown that children with ADHD have different brain activity during certain tasks. Brain development factors such as low birth weight, premature birth and exposure to toxins during pregnancy are also risk factors for the condition. Childhood lead exposure may also be linked with the condition.

While we don’t know what causes ADHD in the brain, we know that it’s diagnosed more often in males than in females. Females may be underdiagnosed. Females with ADHD are more likely to have problems with attention rather than hyperactivity.

Learn more about ADHD diagnosis and treatment