What Causes ADHD?

One of the first questions a parent will have is “Why? What went wrong?” “Did I do something to cause this?” There is little compelling evidence at this time that ADHD can arise purely from social factors or child-rearing methods. Most substantiated causes appear to fall in the realm of neurobiology and genetics. This is not to say that environmental factors may not influence the severity of the disorder, and especially the degree of impairment and suffering the child may experience, but that such factors do not seem to give rise to the condition by themselves.

The parents’ focus should be on looking forward and finding the best possible way to help their child. Scientists are studying causes in an effort to identify better ways to treat, and perhaps someday, to prevent ADHD. They are finding more and more evidence that ADHD does not stem from the home environment, but from biological causes. Knowing this can remove a huge burden of guilt from parents who might blame themselves for their child’s behavior.

Over the last few decades, scientists have come up with possible theories about what causes ADHD. Some of these theories have led to dead ends, some to exciting new avenues of investigation.

Environmental Agents

Studies have shown a possible correlation between the use of cigarettes and alcohol during pregnancy and risk for ADHD in the offspring of that pregnancy. As a precaution, it is best during pregnancy to refrain from both cigarette and alcohol use.

Another environmental agent that may be associated with a higher risk of ADHD is high levels of lead in the bodies of young preschool children. Since lead is no longer allowed in paint and is usually found only in older buildings, exposure to toxic levels is not as prevalent as it once was. Children who live in old buildings in which lead still exists in the plumbing or in lead paint that has been painted over may be at risk.

Brain Injury

One early theory was that attention disorders were caused by brain injury. Some children who have suffered accidents leading to brain injury may show some signs of behavior similar to that of ADHD, but only a small percentage of children with ADHD have been found to have suffered a traumatic brain injury.

Food Additives and Sugar

It has been suggested that attention disorders are caused by refined sugar or food additives, or that symptoms of ADHD are exacerbated by sugar or food additives. In 1982, the National Institutes of Health held a scientific consensus conference to discuss this issue. It was found that diet restrictions helped about 5 percent of children with ADHD, mostly young children who had food allergies.³ A more recent study on the effect of sugar on children, using sugar one day and a sugar substitute on alternate days, without parents, staff, or children knowing which substance was being used, showed no significant effects of the sugar on behavior or learning.⁴

In another study, children whose mothers felt they were sugar-sensitive were given aspartame as a substitute for sugar. Half the mothers were told their children were given sugar, half that their children were given aspartame. The mothers who thought their children had received sugar rated them as more hyperactive than the other children and were more critical of their behavior.⁵

Genetics

Attention disorders often run in families, so there are likely to be genetic influences. Studies indicate that 25 percent of the close relatives in the families of ADHD children also have ADHD, whereas the rate is about 5 percent in the general population.⁶ Many studies of twins now show that a strong genetic influence exists in the disorder.⁷

Researchers continue to study the genetic contribution to ADHD and to identify the genes that cause a person to be susceptible to ADHD. Since its inception in 1999, the Attention-Deficit Hyperactivity Disorder Molecular Genetics Network has served as a way for researchers to share findings regarding possible genetic influences on ADHD.⁸

Recent Studies on Causes of ADHD

Some knowledge of the structure of the brain is helpful in understanding the research scientists are doing in searching for a physical basis for attention deficit hyperactivity disorder. One part of the brain that scientists have focused on in their search is the frontal lobes of the cerebrum. The frontal lobes allow us to solve problems, plan ahead, understand the behavior of others, and restrain our impulses. The two frontal lobes, the right and the left, communicate with each other through the corpus callosum, (nerve fibers that connect the right and left frontal lobes).

The basal ganglia are the interconnected gray masses deep in the cerebral hemisphere that serve as the connection between the cerebrum and the cerebellum and, with the cerebellum, are responsible for motor coordination. The cerebellum is divided into three parts. The middle part is called the vermis.

All of these parts of the brain have been studied through the use of various methods for seeing into or imaging the brain. These methods include functional magnetic resonance imaging (fMRI) positron emission tomography (PET), and single photon emission computed tomography (SPECT). The main or central psychological deficits in those with ADHD have been linked through these studies. By 2002 the researchers in the NIMH Child Psychiatry Branch had studied 152 boys and girls with ADHD, matched with 139 age- and gender-matched controls without ADHD. The children were scanned at least twice, some as many as four times over a decade. As a group, the ADHD children showed 3-4 percent smaller brain volumes in all regions—the frontal lobes, temporal gray matter, caudate nucleus, and cerebellum.

This study also showed that the ADHD children who were on medication had a white matter volume that did not differ from that of controls. Those never-medicated patients had an abnormally small volume of white matter. The white matter consists of fibers that establish long-distance connections between brain regions. It normally thickens as a child grows older and the brain matures.⁹

Although this long-term study used MRI to scan the children’s brains, the researchers stressed that MRI remains a research tool and cannot be used to diagnose ADHD in any given child. This is true for other neurological methods of evaluating the brain, such as PET and SPECT.

ADHD Diagnosis

Some parents see signs of inattention, hyperactivity, and impulsivity in their toddler long before the child enters school. The child may lose interest in playing a game or watching a TV show, or may run around completely out of control. But because children mature at different rates and are very different in personality, temperament, and energy levels, it’s useful to get an expert’s opinion of whether the behavior is appropriate for the child’s age. Parents can ask their child’s pediatrician, or a child psychologist or psychiatrist, to assess whether their toddler has an attention deficit hyperactivity disorder or is, more likely at this age, just immature or unusually exuberant.

ADHD may be suspected by a parent or caretaker or may go unnoticed until the child runs into problems at school. Given that ADHD tends to affect functioning most strongly in school, sometimes the teacher is the first to recognize that a child is hyperactive or inattentive and may point it out to the parents and/or consult with the school psychologist. Because teachers work with many children, they come to know how “average” children behave in learning situations that require attention and self-control. However, teachers sometimes fail to notice the needs of children who may be more inattentive and passive yet who are quiet and cooperative, such as those with the predominantly inattentive form of ADHD.

If ADHD is suspected, to whom can the family turn? What kinds of specialists do they need?

Ideally, the diagnosis should be made by a professional in your area with training in ADHD or in the diagnosis of mental disorders. Child psychiatrists and psychologists, developmental/behavioral pediatricians, or behavioral neurologists are those most often trained in differential diagnosis. Clinical social workers may also have such training.

The family can start by talking with the child’s pediatrician or their family doctor. Some pediatricians may do the assessment themselves, but often they refer the family to an appropriate mental health specialist they know and trust. In addition, state and local agencies that serve families and children, as well as some of the volunteer organizations listed at the end of this document, can help identify appropriate specialists.

Specialty	Can Diagnose ADHD	Can prescribe medication, if needed	Provides counseling or training
Psychiatrists	yes	yes	yes
Psychologists	yes	yes*	yes
Pediatricians or Family Physicians	yes	yes	no
Neurologists	yes	yes	no
Clinical Social workers	yes	no	yes

* As of October 2006, Louisiana and New Mexico laws and regulations allow psychologists who have completed specific training and meet other requirements to prescribe psychotropic medications. The other 48 states and the District of Columbia allow only physicians to prescribe medications.

Knowing the differences in qualifications and services can help the family choose someone who can best meet their needs. There are several types of specialists qualified to diagnose and treat ADHD. Child psychiatrists are doctors who specialize in diagnosing and treating childhood mental and behavioral disorders. A psychiatrist can provide therapy and prescribe any needed medications. Child psychologists are also qualified to diagnose and treat ADHD. They can provide therapy for the child and help the family develop ways to deal with the disorder. But psychologists are not medical doctors and must rely on the child’s physician to do medical exams and prescribe medication. Neurologists, doctors who work with disorders of the brain and nervous system, can also diagnose ADHD and prescribe medicines. But unlike psychiatrists and psychologists, neurologists usually do not provide therapy for the emotional aspects of the disorder.

Within each specialty, individual doctors and mental health professionals differ in their experiences with ADHD. So in selecting a specialist, it’s important to find someone with specific training and experience in diagnosing and treating the disorder.

Whatever the specialist’s expertise, his or her first task is to gather information that will rule out other possible reasons for the child’s behavior. Among possible causes of ADHD-like behavior are the following:

• A sudden change in the child’s life—the death of a parent or grandparent; parents’ divorce; a parent’s job loss
• Undetected seizures, such as in petit mal or temporal lobe seizures
• A middle ear infection that causes intermittent hearing problems
• Medical disorders that may affect brain functioning
• Underachievement caused by learning disability
• Anxiety or depression.

Ideally, in ruling out other causes, the specialist checks the child’s school and medical records. There may be a school record of hearing or vision problems, since most schools automatically screen for these. The specialist tries to determine whether the home and classroom environments are unusually stressful or chaotic, and how the child’s parents and teachers deal with the child.

Next the specialist gathers information on the child’s ongoing behavior in order to compare these behaviors to the symptoms and diagnostic criteria listed in the DSM-IV-TR. This also involves talking with the child and, if possible, observing the child in class and other settings.

The child’s teachers, past and present, are asked to rate their observations of the child’s behavior on standardized evaluation forms, known as behavior rating scales, to compare the child’s behavior to that of other children the same age. While rating scales might seem overly subjective, teachers often get to know so many children that their judgment of how a child compares to others is usually a reliable and valid measure.

The specialist interviews the child’s teachers and parents, and may contact other people who know the child well, such as coaches or baby-sitters. Parents are asked to describe their child’s behavior in a variety of situations. They may also fill out a rating scale to indicate how severe and frequent the behaviors seem to be.

In most cases, the child will be evaluated for social adjustment and mental health. Tests of intelligence and learning achievement may be given to see if the child has a learning disability and whether the disability is in one or more subjects.

In looking at the results of these various sources of information, the specialist pays special attention to the child’s behavior during situations that are the most demanding of self-control, as well as noisy or unstructured situations such as parties, or during tasks that require sustained attention, like reading, working math problems, or playing a board game. Behavior during free play or while getting individual attention is given less importance in the evaluation. In such situations, most children with ADHD are able to control their behavior and perform better than in more restrictive situations.

The specialist then pieces together a profile of the child’s behavior. Which ADHD-like behaviors listed in the most recent DSM does the child show? How often? In what situations? How long has the child been doing them? How old was the child when the problem started? Are the behavior problems relatively chronic or enduring or are they periodic in nature? Are the behaviors seriously interfering with the child’s friendships, school activities, home life, or participation in community activities? Does the child have any other related problems? The answers to these questions help identify whether the child’s hyperactivity, impulsivity, and inattention are significant and long-standing. If so, the child may be diagnosed with ADHD.

A correct diagnosis often resolves confusion about the reasons for the child’s problems that lets parents and child move forward in their lives with more accurate information on what is wrong and what can be done to help. Once the disorder is diagnosed, the child and family can begin to receive whatever combination of educational, medical, and emotional help they need. This may include providing recommendations to school staff, seeking out a more appropriate classroom setting, selecting the right medication, and helping parents to manage their child’s behavior.