ADHD Causes, Signs, Symptoms & Side Effects

No one experiences ADHD the same way as someone else. Understanding the signs, symptoms and side effects of ADHD is a key component toward starting the recovery journey.

Understanding ADHD

Learn about ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with daily functioning. ADHD is one of the most common types of neurobehavioral disorders in childhood and is often first recognized and diagnosed in childhood. Effects may last until adulthood.

There are three types of ADHD, distinguished by the symptoms that are most prevalent in the person. Both symptoms and presentation of ADHD will change over time. The types of ADHD include the following:

Predominately Inattentive Presentation: in this form of ADHD, it can be very hard for the person to finish or organize a task, pay attention to the details required, or follow the instructions or conversations that take place. A person with Predominately Inattentive Presentation is easily distractible; forgetting daily routines and details.

Predominately Hyperactive-Impulsive Presentation: a person with this form of ADHD is prone to fidgeting and talking a lot. It can be hard for them to sit still long enough to complete homework or finish dinner. Smaller children may jump, run, or climb objects all of the time. Feeling restless and impulsive may mean that they interrupt other conversations, take items from peers, or speak when it is inappropriate to speak. It can be hard to listen to directions or wait their turn. Thanks to the impulsive nature of this form of ADHD, a person is more likely to have injuries and accidents than other people.

Combined Presentation: in this form of ADHD, the symptoms described for Predominately Inattentive and Predominately Hyperactive-Impulsive are present in equal amounts.

Each feature of this disorder has a variety of different symptoms. Inattention is defined as wandering off task, lacking persistence, having difficulty sustaining focus, and being disorganized. Hyperactivity is excessive motor activity when it is not appropriate, excessive fidgeting, or excessive talkativeness. Finally, impulsivity is the hasty actions that occur in the moment without any previous consideration that can be potentially harmful to the individual. Impulsivity can stem from the inability to delay gratification or can be displayed as making important decisions without thought for long term consequences.

In order to receive the diagnosis of ADHD, the disorder must have begun in childhood with a majority of the symptoms occurring before 12 years of age. Expressions of these symptoms must be present in more than one setting, with symptoms varying depending on the context within a given setting. However, symptoms may be absent when an individual is receiving rewards for good behavior or is engaged in especially interesting activities. Although ADHD always starts in childhood it is possible that it may not be diagnosed until later in life.

ADHD may first be noticeable when a child is a toddler, but it can be hard to distinguish normative behavior before the age of 4. It is most recognized in elementary school when the inattention becomes more prominent and begins to cause impairment. ADHD is relatively stable throughout early adolescence. In most individuals the symptoms of motoric hyperactivity become less obvious, however, problems with restlessness, inattention, poor planning, and impulsivity seem to remain. There is a significant portion of children with ADHD who continue to present with problems into adulthood.


ADHD statistics

The percentage of children who have been thought to have ADHD has changed over time. It’s now estimated that between 3% and 7% of school-aged children have ADHD.

It is estimated that ADHD occurs in the general population in about 2.5% of adults. In the general population, ADHD occurs more frequently in males than in females with about a male-to-female ratio of 1.6:1. Females, however, are more likely than males to present with inattentive features.

Causes and Risk Factors

Causes and risk factors for ADHD

Genetics: Research has shown that there is a strong genetic component that may cause ADHD in individuals who have family members with the same disorder. If one or both parents have ADHD, their child is more likely to develop the disorder.

Brain Structure: Research has shown that certain areas of the brain may cause ADHD. Certain areas of the brain, such as the frontal lobe, basal ganglia, caudate nucleus, and cerebellum are involved in regulating behavior.

Neurotransmitters: Another hypothesis is that individuals with ADHD have abnormal functioning of certain neurotransmitters or atypical functioning of the nervous system. These abnormalities are thought to cause ADHD as they play a role in regulating behavior. Any abnormalities in these areas may suggest an individual would not be able to regulate their behavior. Dopamine may also play a role in causing ADHD because it is the brain chemical that carries signals between the nerves and the brain. Dopamine is linked to functions such as movement, sleep, mood, attention, and learning all of which are a part of ADHD.

Signs and Symptoms

Signs and symptoms of ADHD

There are a variety of signs and symptoms that can occur in individuals with ADHD. The severity and frequency of symptoms displayed depend on upon the individual. Some of the symptoms include:

Inattentive symptoms

  • Fails to pay close attention to details or makes careless mistakes
  • Difficulty sustaining attention
  • Doesn’t seem to listen when directly spoken to
  • Does not follow through on instructions
  • Fails to complete school work or workplace tasks
  • Difficulty organizing tasks and activities
  • Often avoids or dislikes tasks that involve sustained mental effort
  • Frequently loses things
  • Easily distracted by irrelevant stimuli
  • Forgetful in daily activities

Hyperactive-impulsive symptoms

  • Fidgets or taps hands or feet
  • Leaves seat in situations when sitting is required
  • Runs or climbs objects in inappropriate settings
  • Unable to quietly engage in activities
  • Often talks excessively
  • Often interrupts or intrudes upon others
  • Blurts out answers before question is finished
  • Difficulty waiting one’s turn


Effects of ADHD

If the symptoms of ADHD are not properly managed they can cause a variety of problems in an individual’s life. Some effects include:

  • Social rejection and isolation
  • Substance abuse
  • Incarceration
  • Poor occupational performance
  • Academic problems
  • Elevated interpersonal conflict
  • More traffic accidents and violations
  • Family and relationship challenges
  • Physical and mental health problems

Co-Occurring Disorders

ADHD and co-occurring disorders

It is common for adults with ADHD to present with co-occurring disorders. The most common co-occurring disorders are:

  • Intermittent explosive disorder
  • Substance abuse disorder
  • Personality disorders (especially antisocial personality disorder)
  • Obsessive-compulsive disorder
  • Tic disorders
  • Autism spectrum disorder