Schizophrenia: Causes

Pathogenesis (development of the disease)

Schizophrenia is the result of a multifactorial event, in the development of which not only environmental influences but also genetic factors play an important role. The genetic burden from parents and grandparents is estimated to be at least 80%. SNPs (single nucleotide polymorphism; see below) can currently explain 30-50% of the genetically determined risk of schizophrenia.The “vulnerability-stress-coping model” according to Zubin and Nücherlein includes several factors in the development of the disease. These include, above all, a genetic component as well as developmental disorders. Histological examinations have revealed a number of changes in the brain, such as brain atrophy (brain shrinkage) and, above all, a reduction in the volume of the hippocampus (part of the brain; located in the temporal lobe and a central switching station of the limbic system; the limbic system is used to process emotions and generate drive behavior) and the amygdala (corpus amygdaloideum (amygdala nucleus); part of the limbic system; plays a key role in the development of anxiety). In addition, various neurotransmitters (messenger substances) are also thought to have an influence on the development of schizophrenia, but there are contradictory statements about this. It is possible that there is a relative GABA (gamma-amino-butyric acid) deficiency in the brain; in one study on this, the severity of the deficiency correlated with clinical symptoms.

Etiology (Causes)

Biographic Causes

  • Genetic burden from parents, grandparents (estimated to be at least 80%); SNPs (single nucleotide polymorphism) can currently explain 30-50% of the genetic risk of schizophrenia
    • Risk of disease increases with the degree of genetic relatedness to a person who has schizophrenia
      • For monozygotic twins, the concordance rate is approximately 50%
      • Children of two affected parents 27.3%
      • Children of one affected parent 7.0 %
      • First-degree relatives about 9%
      • Relatives third degree about 2%
    • Genetic risk depending on gene polymorphisms:
      • Genes/SNPs (single nucleotide polymorphism; English : single nucleotide polymorphism):
        • Genes: DRD2
        • SNP: rs6277 in the gene DRD2
          • Allele constellation: CT (1.4-fold).
          • Allele constellation: CC (1.6-fold)
    • Genetic diseases
      • Microdeletion syndrome 22q11 – changes on the long arm of chromosome 22 at position 11: Absence of a gene (knockout of the DGCR8 gene) that normally prevents uncontrolled brain activity in the cortex (cerebral cortex); consequences include abnormalities of the heart and face, thymic aplasia (partial or complete absence of the thymus), cleft palate, hypocalcemia (calcium deficiency), and primary hypoparathyroidism (parathyroid insufficiency), as well as developmental delays; Furthermore, there is a 30-fold increased risk of developing psychosis compared to the general population; prevalence 1 in 3. 000 people
  • Higher age of parents at birth
  • Pregnancy or birth complications such as intrauterine malnutrition or rhesus factor incompatibility (rhesus incompatibility)
  • Birth in winter or early autumn
  • Ethnic minority status
  • Early developmental disabilities
  • Low intelligence

Behavioral causes

  • Consumption of stimulants
    • Tobacco (smoking)
  • Drug use
    • Amphetamines e.g. Ectasy (synonym: Molly; MDMA: 3,4-methylenedioxy-N-methylamphetamine) or similarly acting sympathomimetics; metamphetamines (“crystal meth”).
    • Cannabis (hashish and marijuana).
  • Psycho-social situation

Causes related to disease

  • Epilepsy (seizure disorder)
  • Psychotic disorders such as schizoaffective disorder or schizoid personality disorder

Other causes