In the past, people understood little about how plants and animals worked. Doctors described mental illnesses but remained in the dark about their causes and even about which part of the body was wrong. Today we can study the living brain. First, imaging techniques appeared that showed the structures of the brain. However, this could not explain the cause, because the brains of people with ADHD are the same. But in the late 1980s, new ways to image the brain were invented. These showed what was happening in the brain, and doctors found that the brains of people with ADHD were different in this respect. In addition, doctors learned more about how diseases are transmitted, for example from one person to another through infection, or from parents to children through genes.
This gave scientists and doctors a good insight into the causes and nature of conditions such as ADHD that influence how people feel, how they think and how they behave.
In the genes
When you look at the families of children with ADHD , you usually find at least one close relative with a similar problem: a father who always got into trouble at school; a cousin who had difficulty learning; an uncle who constantly got into fights. The identical twin brother or sister of an ADHD patient , who has exactly the same genetic material, will almost always (in 90 percent of cases) also have this condition.
From this we deduce that ADHD is hereditary – that is, this condition is passed on from parent to child via the genes. Genes are small pieces of information contained in every cell of the body that contain instructions for creating a unique individual, allowing him or her to grow and function. Genes don’t explain everything about why some people get a disease and others don’t, but they do explain a lot.
Environmental factors and ADHD
Genes determine whether people have a high or small chance of developing a certain disease and suffering greatly from it. Education and the environment also play a role. For example, a child with ADHD whose parents are sympathetic, whose school is helpful, and whose family and friends are tolerant, will do better than a child whose parents are irritable or hostile and who is reprimanded by teachers and criticized by everyone. turned down.
The normal brain
The human brain is constantly bombarded with information: everything you see, hear and feel. The brain also receives messages from inside your body (for example, when you are hungry or catch a cold) and from your memory (for example, who people are). It’s a bit like hearing different radio stations overlapping each other.
The brain prevents overload by selecting the important messages and ignoring the rest. This requires several specialized areas of the brain to work together. The brain’s control center tells the different parts of the brain which information needs to be delivered quickly and which information needs to be filtered out. The other parts of the brain carry out these instructions.
The control center of the brain is called the frontal lobes (in the front of the head, behind the forehead).
ADHD brain
In the brain of someone with ADHD, information flows in without much being filtered out. It’s somewhat similar to watching a split-screen television, showing a lot of different scenes at once. The information is recorded, but because there is so much of it, the child may react impulsively without weighing the consequences. Another possibility is that he or she is not
responding to any of the messages flooding his or her brain. He or she is impulsive or inattentive – or perhaps both. An ADHD patient’s brain is overloaded with unfiltered information. Sometimes it seems impossible to deal with this.
Images of the brain
The latest imaging techniques scan the brain and show where there is activity and where there is not.
A technique called SPECT (Single Photon Emission Computed Tomography) measures blood flow to different parts of the brain. Another technique, PET (Positron Emission Tomography), makes tiny sugar molecules that have been provided with a radioactive label visible. The sugar accumulates in the parts of the brain that are most active and makes them light up. By showing whether the lights are on or off in key areas, SPECT and PET images tell us three things about the brains of people with ADHD:
- the frontal lobes (control center) of the brain are less active in ADHD brains than in normal brains
- the areas that collect information from images and sounds are extremely overloaded, indicating that much unnecessary information is not being filtered out.
- When stimulants are used, these differences usually disappear.
Neurotransmitters: the brain’s messengers
It is an oversimplification to see the brain only as a control center and a number of areas that carry out commands. The brain also works as a whole – much like an electronic synthesizer producing a complex sound made up of many tracks put together.
In the brain, billions of different specialized cells transmit messages to each other, which is somewhat comparable to what happens in a telephone exchange or computer. These cells – neurons – communicate with each other via chemical messengers called neurotransmitters.
Between every two brain cells there is a small opening called a synapse. When a neuron wants to send a message to an adjacent cell, it releases a neurotransmitter that crosses the synapse and stimulates the adjacent cell. This process causes a chain reaction between the brain cells. More than 50 different types of neurotransmitter have been identified, each responsible for different behaviors or feelings, and active in different areas of the brain.
Dopamine and norepinephrine
The problems associated with ADHD are caused by an imbalance of the chemical messengers dopamine and norepinephrine in the frontal lobes (the control center) and other key areas of the brain. Noradrenaline is also called norepinephrine. Due to a
lack of dopamine, a child with ADHD is unable to select the important messages from the flow of information that bombards the brain. The child cannot filter out the irrelevant background noise and cannot concentrate on what is important. Children with ADHD do not have enough dopamine, but too much dopamine is also bad. This makes people obsessive: they concentrate too much on one thing – for example, they try to keep their hands clean even when they are not dirty.
Norepinephrine plays a different role. It is the chemical messenger that triggers ‘fight or flight’ responses – the instinct of cornered animals to fight or run away. Norepinephrine prepares you for action. Too little makes people indifferent and lethargic; too much makes them crave excitement even when it is misplaced or even dangerous. When these two important brain chemicals are out of balance, a person will have difficulty paying attention,
and/or will be impulsive and hyperactive.
Dopamine levels
Dopamine levels increase when you are happy and relaxed. The proof comes from people petting their pets. Scientists in South Africa found that both dogs and their owners had lower blood pressure and higher dopamine levels after relaxing together for half an hour.
Upbringing and environment
The main cause of ADHD is an abnormality in brain function that affects behavior. This abnormality is inherited – in other words, it is genetic . But other factors must also be taken into account.
Over the past century, experts began to recognize that upbringing and environment are important factors that help children grow up healthy and happy. Now we know that the environment is as important as the genes inherited from the parents. Even a condition like ADHD, which has a known genetic cause, is influenced by the environment. In particular, the behavior of parents, family and teachers can have a positive or negative influence.
However, it can be difficult for parents of ADHD patients to always remain patient. Difficult children – even children who are not sick – can make their parents feel inadequate. And because ADHD runs in the family, one parent may also struggle with ADHD problems.
Problems during birth
It is often the case that the mother of a child with ADHD has had a difficult pregnancy or delivery. It is thought that the risk of having a child with ADHD is increased if the mother smokes during pregnancy or is exposed to some industrial toxins, such as those found in herbicides. If the baby does not get enough to eat after birth, the risk also increases.
Is ADHD caused by diet?
In the 1970s, American allergy expert Ben Feingold said that hyperactivity was caused by preservatives naturally occurring in food or by additives – chemicals added to food to extend its shelf life or give it color. For a while, studies seemed to support this idea, but eventually thorough research showed that up to five in a hundred hyperactive children were negatively affected by their diet, and only slightly. Although some children with behavioral problems are sensitive to certain substances in food, whether added or naturally occurring, experts now believe that many of these cases are not true cases of ADHD. Nevertheless, parents of many children with ADHD remain convinced that there are foods that worsen symptoms.
