Schizophrenia is a chronic, severe and disabling psychiatric disorder in which affected individuals interpret reality in an abnormal way. The disease can cause a combination of hallucinations, delusions and severe disturbances of thought and behavior. This can cause fear and make sufferers withdrawn and easily irritable. It affects about 24 million people worldwide.

The exact causes of the disease are unknown, but it is thought to be the result of a combination of genetics and environmental and/or psychosocial factors that cause dysregulation of brain physiology. Studies carried out to date show that an imbalance in neurotransmitter levels occurs in those affected.

Risk factors that may contribute to the development of this disorder include:

  • Presence of other undiagnosed mental disorders.
  • Some complications during pregnancy and birth, such as malnutrition or exposure to toxins or viruses that may affect brain development.
  • Use of psychoactive or psychotropic drugs during adolescence and young adulthood.

Although the genetic factors influencing the disease are not entirely clear, the hereditary nature of the pathology is well established. Twin studies have shown that the risk in twins is 50% if the other sibling is affected. Along these lines, the GWAS studies carried out to date have identified numerous associated genetic markers. In an association study carried out on more than 33,000 patients and 77,000 controls, 90 susceptibility loci have been identified. Among the genes identified, the one showing the strongest association was PGBD1, which codes for a transposase highly expressed in the brain, but of unknown function. Genes associated with brain connectivity, such as CACNA1C and CNNM2, also stood out.


Schizophrenia is usually diagnosed before the age of 30 years, being very rare in children and after 45 years. Symptomatology includes problems with thinking, behavior and emotions. Signs and symptoms can vary. The most common are the following:

  • Fantasies: those affected present false beliefs that have no basis in reality, such as believing that they are being harassed or that a catastrophe is going to occur.
  • Hallucinations, which involve seeing or hearing things that do not exist. They can involve any of the senses, but hearing voices is usually the most common.
  • Disorganized or abnormal motor behavior, which may include resistance to following instructions, inappropriate posture or unresponsive movement.
  • Impaired communication, with meaningless conversations.
  • Negative symptoms are associated with disruption of normal emotions and behaviors. They are more difficult to recognize. People who have negative symptoms need help with daily tasks.
  • In adolescents, social withdrawal, decreased school performance, irritability and lack of motivation may occur.

It is common for symptoms to change over time with respect to type and severity, alternating periods of worsening and remission.


The exact causes of schizophrenia are unknown, so total prevention of the disease is not possible. Several factors are known to contribute to its onset. Among the non-modifiable ones, the best known is genetic predisposition: 10% of people with schizophrenia have a close relative (parents, siblings) who has been diagnosed with it.

There are also a number of actions that can help to decrease the risk of onset of the disease:

  • Control in pregnancy and after childbirth that allow to avoid complications such as malnutrition of the baby, preeclampsia or early approach of possible neonatal infections.
  • Avoidance of drugs such as cannabis, alcohol or cocaine.
  • Avoid exposure to traumatic events in children and adolescents.
  • Maintain good social relationships, which help to have a good self-esteem, reduce stress and not feel alone.
  • Stress management.
  • Use of protective measures for head injuries, such as helmets when riding a bike or motorcycle.
  • Healthy lifestyle, with regular exercise and eating healthy foods.

Schizophrenia requires lifelong treatment, even if symptoms disappear. The multidisciplinary treatments available, which include pharmacological and psychiatric approaches, help to control the disease very effectively and prevent the onset of outbreaks.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

90 loci


Yao X, Glessner JT, Li J, et al. Integrative analysis of genome-wide association studies identifies novel loci associated with neuropsychiatric disorders. Translational Psychiatry. 2021 Jan;11(1):69.

Marder SR, Cannon TD. Schizophrenia. N Engl J Med. 2019 Oct 31;381(18):1753-1761.

National Institute of Mental Health (NIH) [April 2022]

American Psychiatric Association [April 2022]

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