What gene causes autism

Psychiatry, Psychosomatics & Psychotherapy

Causes of Autism Spectrum Disorders

There are different explanations for the development of autism, but there is no one single cause. Rather, it can be assumed that autism spectrum disorders can have very different causes. It is known that various biological factors play an essential role. Psychosocial factors, on the other hand, only play a certain role in the development of certain comorbid symptoms, such as fearful or aggressive behavior; although here, too, a more biological basis can be assumed.

Hereditary factors are considered to be a major cause of autistic disorders. Parents with Autism Spectrum Disorder have a greatly increased risk of having a child with Autism Spectrum Disorder. Identical twins typically both develop autism spectrum disorder. However, there are a few exceptions, which are probably due to epigenetic changes, different birth weights and other environmental factors. A complex interplay of different genes and environmental factors is probably responsible for the disease. The heritability of autism spectrum disorders is currently estimated to be around 70-80%. There are a number of mutations and chromosomal microdeletions and duplications that increase the risk of developing an autism spectrum disorder. Individual molecular genetic causes, such as the fragile X syndrome, which occurs in around 3% of all people with autism spectrum disorder, have already been largely clarified, in particular with regard to their consequences on the development of the nervous system, and they are currently already being identified Researching new drugs that are to be used specifically for the treatment of patients with fragile X syndrome. However, these are not yet approved for treatment, but are currently only being tested in studies. Other known monogenic diseases associated with increased rates of autism spectrum disorders are tuberous cerebral sclerosis, neurofibromatosis, and Smith-Lemli-Opitz syndrome. Some genetic syndromes, which are characterized by small duplications or a lack of genetic information, are also increasingly found in autism spectrum disorders, such as Velo-Cardio-Facial Syndrome or Prader-Willi Syndrome or a duplication of chromosomes 15q11-13.

Parental age at the birth of the child

The influence of older fathers on increased rates of autism spectrum disorders has recently been confirmed in a meta-analysis. Other studies found effects for both older maternal and paternal age. Epigenetic changes or new mutations are discussed as possible pathogenic mechanisms.

Risk factors in pregnancy and childbirth

Certain maternal infectious diseases during pregnancy, such as rubella infection, are known to be risk factors for autism spectrum disorders. A Danish registry-based study found an increased risk after severe viral infections in the first trimester and severe bacterial infections in the second trimester. Several population-based studies have also shown that (severe) prematurity increases the risk of autism spectrum disorders. Maternal diabetes as well as postpartum hypoglycaemia and lung function problems in term-born children have been described as general pregnancy-associated risk factors. Another study discusses the use of serotonin reuptake inhibitors during pregnancy as a risk factor, with the number of children exposed to SSRIs during pregnancy being relatively low. The use of antiepileptic drugs, especially valproate, during pregnancy was also associated with increased rates of autism spectrum disorders in children in clinical studies. So far, alcohol consumption and severe psychosocial stress on the mother have been excluded as pregnancy-associated risk factors.

In some people with autism, disorders of fine and gross motor skills and irregularities in electrical brain waves can be observed. A seizure disorder in approximately 10% of all people with an autism spectrum disorder also speaks for neurological factors. Overall, it is now assumed that brain development in people with autism spectrum disorder proceeds differently from prenatal than in healthy children. Numerous functional and structural imaging studies of the brain have shown changed functions and structures, especially in the two temporal lobes as well as the frontal lobes of the cerebrum and the cerebellum in children, adolescents and adults with autism spectrum disorder. The cells of the cerebral cortex have a different function and appearance than those of people of the same age, sex, and cognitive skills who do not have an autism spectrum disorder. These changes in brain function are also the basis for the observed behavioral abnormalities and cognitive peculiarities, such as good shape recognition skills, but difficulties in perceiving movement; the good logical and reasoning skills, but the difficulties of planning action and goal orientation and other cognitive peculiarities and limitations.

Technical support: Prof. Dr. med. Dipl. Theol. Christine M. Freitag, Frankfurt (DGKJP)