What Is Schizophrenia?

  • 1st Revision: Human Maryam Ikram

Schizophrenia is a complex, chronic mental illness characterised by a spectrum of symptoms including delusions, hallucinations, disorganised speech or behaviour and a decline in personal hygiene.1 Yet, the causes of schizophrenia are still unclear. Research suggests several possible factors that can contribute to the development of this condition.  

Currently, research has determined a combination of factors that could alter an individual's mental health state. It has been identified that schizophrenia could manifest due to physical, genetic, psychological, and environmental factors.1 Some people may be susceptible to schizophrenia and a stressful life event might trigger a psychotic episode which is considered the major factor that can contribute to the development of schizophrenia.

Stigma, discrimination and abuse of people with schizophrenia are common  causing social exclusion and impacting their relationships with others, including family and friends. Therefore, it is important to talk openly about mental health issues like schizophrenia. 


 Schizophrenia is a mental health disorder that encounters a wide range of symptoms. The symptoms of schizophrenia can be split into two groups: positive symptoms (delusions and hallucinations) and negative symptoms (social withdrawal, confused speech).2  About 1% of the world's population is affected by schizophrenia, which can reduce life expectancy by 20 years. Despite the limited understanding of the complex pathogenesis of schizophrenia, over the past decades, researchers have developed multiple treatment options for the disease, either pharmacologically (with drugs) or psychosocially (with therapy).3 

Causes of schizophrenia

The exact origin of schizophrenia is unknown. However, there are some risks associated with developing schizophrenia.


Although schizophrenia tends to run in families, it is not believed to be caused by a single gene.4 Different combinations of genes are more likely to make you more susceptible to this disease. However, the presence of these genes does not necessarily result in schizophrenia. 

Evidence that the disorder is partially inherited comes from studies of twins. Identical twins have the same genes and if one twin develops schizophrenia, the other twin has a 50% chance of developing it . This is true even if they are separated. 

For non-identical twins with different genetic makeups, if one twin develops schizophrenia, the other has only a 1 in 8 chance of developing schizophrenia. This is higher than in the general population, where the odds are around 1 in 100, but it suggests that genes are not the only factors influencing the development of schizophrenia.2 

Brain development 

Studies of people with schizophrenia have shown subtle differences in brain structure. These changes do not occur in everyone with schizophrenia and may occur in people who do not have a mental illness.4


There is a link between neurotransmitters and schizophrenia, as drugs that alter neurotransmitter levels in the brain are known to alleviate some of the symptoms of schizophrenia.54

Research suggests that schizophrenia may be caused by changes in the levels of two neurotransmitters: dopamine and serotonin.1

Some research suggests that an imbalance between the two may be at the root of the problem. Some have found that changes in the body's sensitivity to neurotransmitters are part of the cause of schizophrenia.4  

Pregnancy and birth complications

Studies have shown that people who develop schizophrenia are more likely to have complications before and during birth, including.

  • Premature birth
  • Low birth weight 
  • Oxygen deprivation (asphyxia) during childbirth
  • Exposure to viruses or infections6

These factors are known to affect brain development.

Triggers that could provoke schizophrenia: 

  • Stress6


Studies have shown that drugs may increase the chances of  developing schizophrenia or  similar illnesses.7

Signs and symptoms of schizophrenia

Schizophrenia changes the way a person thinks and behaves. The condition can progress slowly. The first signs often start in the teenage years, so they can be hard to spot. Symptoms  such as social withdrawal, lack of responsiveness and changes in sleep patterns can be mistaken for "stages" of puberty. 

Symptoms of schizophrenia are usually classified as:

  • Positive symptoms - changes in behaviour or thinking, such as hallucinations or delusions
  • Negative symptoms  - when people withdraw from the world around them, are indifferent to routine, social interactions and often appear emotionless and flat 


A hallucination  is seeing, hearing, smelling, tasting, or feeling something that does not exist outside your mind. The most common hallucination is hearing voices. Hallucinations are very real to those experiencing them, even if those around them cannot hear voices or perceive sensations.

Studies have shown that when people with schizophrenia hear voices, language areas in the brain change. These studies show that the experience of hearing voices appears real as if the brain mistakes thoughts for real voices. Some people describe the voices they hear as friendly and pleasant, but more often they are rude, judgmental, abusive, or annoying.

The voice may describe the activity being performed, discuss the listener's thoughts and actions, give instructions, or speak directly to the person. Voices can come from different locations, for example the television.


A delusion  is a belief held with complete certainty even if it is based on a false, strange, or unrealistic view and it can affect a person's behaviour. Delusions may begin suddenly or develop over weeks or months. Some people develop delusional ideas to explain the hallucinations they are having. Those suffering from paranoid delusions may believe they are being harassed or stalked. They may think that they are the only ones carrying the message on television or in newspaper articles or that the colours of the cars on the street hide the message. 

Disorganised thinking (language)

Disorganised thought is inferred from disorganised language. Effective communication may be compromised and answers to questions may become partially or completely irrelevant. On rare occasions, when speaking, people with schizophrenia combine meaningless words that they cannot understand, also known as a word salad.

Extremely disorganised or abnormal motor behaviour

This can manifest itself in many ways, from childish silliness to unpredictable excitement. A person with schizophrenia will have difficulty completing tasks because actions are not directed toward personal goals. Behaviours include inappropriate or odd postures, complete lack of response, or excessive movement to no avail. 

Negative symptoms

It refers to a reduced or absent ability to function normally. For example, people with schizophrenia may disregard personal hygiene or appear to lack emotion (no eye contact, no change in facial expressions and monotonous speech). 


Schizophrenia is often described by doctors as a form of psychosis. The first acute episode of psychosis can be very difficult to deal with for both the patient and their family and friends. Dramatic changes in behaviour can occur, and the person may become agitated, anxious, confused, angry and suspicious of those around them. People with schizophrenia may not think they need help and it may be difficult to persuade them to see a doctor.  

Management and treatment for schizophrenia

Schizophrenia requires lifelong treatment even after symptoms have resolved. Treatment  with drugs and psychosocial therapy can help manage the condition.2 Nearly two-thirds of first-episode schizophrenia patients achieve remission after 4 to 10 weeks of antipsychotic treatment. Two-thirds are fine after a year of treatment.9 In some cases, hospitalisation may be required. 

Treatment  is usually led by a psychiatrist with experience treating schizophrenia. The treatment team may also include a psychologist, a social worker, a psychiatric nurse, and possibly a case manager who coordinates care. A full team approach may be available in clinics experienced in treating schizophrenia. 


How is schizophrenia diagnosed?

There is no single test for diagnosing schizophrenia, however, it involves several assessments that could determine the condition. Schizophrenia can be diagnosed if you experience one or more of the symptoms;  hallucinations, hearing voices, delusions and inability to take care of yourself and maintain basic hygiene. You would be referred to a mental health specialist that would examine you by:

  • Psychiatric evaluation
  • Diagnostic criteria for schizophrenia
  • Tests and screenings 

How can I prevent schizophrenia?

There is no cure to prevent schizophrenia completely, yet, sticking to a treatment regimen can help prevent flare-ups and worsening symptoms. However, if you have a family history of schizophrenia, there are some things you can do  to avoid triggering psychosis: 

  • Do not use drugs
  • Avoid abusive or traumatic situations
  • Maintain strong social ties
  • Learn how to deal with stress 

Who is  at risk of schizophrenia?

  • Having a family history of schizophrenia
  • Some pregnancy and childbirth complications, such as malnutrition and exposure to toxins and viruses can affect brain development
  • Psychotropic drugs (for example, heavy cannabis consumption) used during teenage and young adulthood
  • Psychosocial factors (such as stress) may influence the onset and course of schizophrenia

How common is schizophrenia?

As stated by World Health Organisation (WHO) schizophrenia affects approximately 24 million people worldwide, or 1 in 300 (0.32%) and is not as common as other mental health issues. It often begins in late adolescence or in the 20s and tends to occur earlier in people assigned male at birth  rather than in people assigned female at birth. . Only 31.3% of people with psychosis receive specialised psychiatric care.10  

What can I expect if I have schizophrenia?

 Schizophrenia is a mental disorder that is characterised by significant impairments in the perception of reality and changes in behaviour associated to: 

  • Chronic delusions
  • Chronic hallucinations
  • Disorganised thinking and/or speech 

When should I see a doctor?

People with schizophrenia are often unaware that their difficulties stem from a mental disorder that requires treatment. Therefore, it is often necessary to seek help from family and friends. 


Most people with schizophrenia recover, but many experience occasional symptoms (relapses). Support and treatment can help manage the mental health condition and its impact on an individual's life.  Taking proper care for individuals with schizophrenia can help them feel better and help to reduce anxiety, depression and fatigue. It improves their quality of life and helps them to become more active and independent. 

As part of a care program for  people with schizophrenia, the person will have to be in regular contact with the medical team. A good relationship with the team means they can easily discuss symptoms and concerns. The more they know, the more they can help. 


  1. Patel KR, Cherian J, Gohil K, Atkinson D. (2014). Schizophrenia: overview and treatment options. P T. Sep;39(9):638-45. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4159061/
  2. Ghanbarzehi, A., Sepehrinezhad, A., Hashemi, N., Karimi, M., & Shahbazi, A. (2023). Disclosing common biological signatures and predicting new therapeutic targets in schizophrenia and obsessive–compulsive disorder by integrated bioinformatics analysis. BMC Psychiatry, 23(1). Available from: https://bmcpsychiatry.biomedcentral.com/articles/10.1186/s12888-023-04543-z 
  3. Pan, J. (2022). An overview of schizophrenia treatment options. 4th International Conference On Frontiers Of Biological Sciences And Engineering (Fbse 2021). Available from: https://aip.scitation.org/doi/abs/10.1063/5.0094794
  4. Millan, M. J., Andrieux, A., Bartzokis, G., Cadenhead, K., Dazzan, P., Fusar-Poli, P., Gallinat, J., Giedd, J., Grayson, D. R., Heinrichs, M., Kahn, R., Krebs, M.-O., Leboyer, M., Lewis, D., Marin, O., Marin, P., Meyer-Lindenberg, A., McGorry, P., McGuire, P., Weinberger, D. (2016). Altering the course of schizophrenia: Progress and perspectives. Nature Reviews Drug Discovery, 15(7), 485–515. Available from: https://www.nature.com/articles/nrd.2016.28 
  5. Stilo, S. A., & Murray, R. M. (2019). Non-genetic factors in schizophrenia. Current Psychiatry Reports, 21(10). Available from: https://link.springer.com/article/10.1007/s11920-019-1091-3 
  6. Cheslack-Postava, K., & Brown, A. S. (2022). Prenatal infection and schizophrenia: A decade of further progress. Schizophrenia Research, 247, 7–15. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0920996421001742 
  7. Müller, H., Sperling, W., Köhrmann, M., Huttner, H. B., Kornhuber, J., & Maler, J.-M. (2010). The synthetic cannabinoid spice as a trigger for an acute exacerbation of cannabis induced recurrent psychotic episodes. Schizophrenia Research, 118(1-3), 309–310. Available from: https://www.sciencedirect.com/science/article/abs/pii/S092099640900591X 
  8. Lincoln, T. M., Sundag, J., Schlier, B., & Karow, A. (2017). The relevance of emotion regulation in explaining why social exclusion triggers paranoia in individuals at clinical high risk of psychosis. Schizophrenia Bulletin, 44(4), 757–767. Available from: https://academic.oup.com/schizophreniabulletin/article/44/4/757/4372293 
  9. Kahn, R. S. (2020). On the origins of schizophrenia. American Journal of Psychiatry, 177(4), 291–297. Available from: https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.2020.20020147 
  10. Jaeschke, K., Hanna, F., Ali, S., Chowdhary, N., Dua, T., & Charlson, F. (2021). Global estimates of service coverage for severe mental disorders: Findings from The Who Mental Health Atlas 2017. Global Mental Health, 8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8320004/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Karina Silova

MSc Molecular Medicine and BSc Biomedicine, University of East Anglia, UK

My background is in key areas of biomedical research focusing on diseases and their molecular pathways to understand their root cause. I specialise in epigenetics and reproductive health; I am passionate about understanding diseases and helping to bridge the gap between medical science and the general public with accurate and understandable content while educating the public about health and diseases.

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