What are the neurological foundations of ADHD

Psychiatry, Psychosomatics & Psychotherapy

The causes and development mechanisms of ADHD are not yet fully understood. Researchers today assume that a large number of individual genetic influencing factors interact with other influencing factors, e.g. with pregnancy and childbirth complications or environmental factors, and that developmental deviations in neuronal control circuits that are responsible for the development of the symptoms occur. These deviations in the development of neuronal control circuits include changes in the neurotransmitter system (the messenger substances that create a connection between the individual brain cells) that have been detected in children with ADHD. According to today's view, various pathways can lead to the clinical appearance of ADHD. This also means that not all those affected are based on the same neuropsychological and neurobiological abnormalities of the symptoms. These abnormalities are not specific to ADHD, but can also occur in other disorders.

The results of neuroanatomical studies suggest that there are functional disorders of certain neuronal control circuits in ADHD, the essential components of which are the striatum (part of the basal ganglia) and the frontal lobe. However, deviations were also found in the cerebellum and other brain areas of children with ADHD. The relevant control loops play a key role in realizing and controlling the interaction of motivation, emotion, cognition and movement behavior in a neuronal manner. Dysfunctions (functional disorders) of these control circuits go hand in hand with an excess or insufficient supply of messenger substances (neurotransmitters) in certain brain regions. In the case of ADHD, the messenger substances dopamine and norepinephrine are of particular importance.

Due to the metabolic and functional disorders in the brain, those affected are only able to concentrate their attention on one thing to a limited extent; they suffer from impaired self-regulation. At the same time, access to existing skills and information is hindered, making predictive action planning difficult.

Hereditary predisposition

Many studies indicate that hereditary factors play a significant role in the development of ADHD. Convincing evidence of this comes from family, twin, and adoption studies. Twin studies show that a good 80% of identical and almost 30% of dizygotic twins show the same symptoms. Using molecular genetic studies, it was also possible to identify individual regions in the human genome that show typical changes in people with ADHD. Corresponding changes were found, especially in the genetic information that is responsible for the formation and transmission of the messenger substance dopamine. However, the changes identified so far can only explain the development of ADHD to a very limited extent. The interplay between different genes and the interplay of hereditary and environmental factors are probably particularly important for the development of ADHD and only a few research results are available. According to the current state of research, it is assumed that many individual genetic changes work together. These genetic factors are also related to other influencing factors such as pregnancy and childbirth complications or environmental factors.

Complications and stresses during pregnancy and childbirth

Consumption of nicotine, alcohol, or other drugs during pregnancy, as well as lack of oxygen at birth, are likely to increase the child's risk of developing ADHD later. Central nervous infections during pregnancy, traumatic brain injuries and complications during pregnancy and childbirth are also associated with later hyperkinetic abnormalities. However, the majority of children and adolescents with ADHD do not show such stress. In addition, such complications do not always lead to ADHD.

Psychosocial Influences

The development and course of ADHD can be influenced by family and school influences. Family conditions, conditions in kindergarten and school are not the exclusive cause of the disorder, but they can to a large extent influence the severity of the problems and their further course. If parents have psychological problems themselves (e.g. ADHD problems) or if there are many quarrels or heavy financial burdens in the family, the ADHD symptoms of the child or adolescent can be exacerbated. Here, too, an interplay between the factors of the family and school environment, the genetic makeup of the child and possible stresses during pregnancy or birth must be assumed.

The so-called psychosocial risk factors include, for example:

  • Incomplete family, i.e. growing up with a single parent or without parents,
  • Mental illness of a parent, especially antisocial personality disorder of the father,
  • Family instability, constant quarrel between parents
  • Low family income, very cramped living conditions
  • Inconsistent upbringing, lack of rules
  • Frequent criticism and punishment