Experts have not identified any specific genes that directly cause schizophrenia, but they believe many, possibly thousands, of genes can contribute in small amounts to your total risk.
Schizophrenia is a serious mental health condition that falls under the umbrella of psychotic disorders. Psychotic disorders feature episodes of psychosis, lapses in reality that affect a person’s thinking, perceptions, and sense of self. Hallucinations, delusions, and disorganized thinking are among the core symptoms of psychosis. In the DSM-5, this condition is actually referred to as “Schizophrenia and Other Psychotic Disorders.”
Less than 1% of people in the United States live with schizophrenia. Globally, the condition affects approximately
While there’s no single, universal cause of schizophrenia, genetics plays a major role in your overall risk.
Genetics accounts for up to
According to a
The genes you inherit from your parents contribute to your heritable genetic risk. Having a first-degree relative (FDR), such as a parent or sibling with schizophrenia is one of the greatest risks for the disorder. According to meta-analysis data from 2020, having one FDR living with schizophrenia increases your individual risk by 8-fold, while having two FDRs living with schizophrenia increases it by 11-fold.
Although the risk of schizophrenia is higher for family members of those with the condition, having an FDR living with schizophrenia does not guarantee that you’ll also develop it.
Schizophrenia is a complex disorder with no known single underlying cause. Environmental factors, changes in your brain’s function and structure, substance use, and genetics can all increase your chance of developing this condition.
Along with genetics, other potential causes of schizophrenia include:
- The environment: Being exposed to viruses or toxins, or experiencing malnutrition before birth, may increase the risk of schizophrenia.
- Brain chemistry: Changes in brain chemicals, such as the neurotransmitters dopamine and glutamate, may cause schizophrenia.
- Brain structure: Differences in brain structure or injury to the brain may cause schizophrenia.
- Substance use: Use of mind-altering (psychoactive or psychotropic) drugs in teens and young adults may increase the risk of schizophrenia.
- Immune system activation: Autoimmune diseases or inflammation may also cause schizophrenia.
Prior to 2013, healthcare professionals divided schizophrenia into five subtypes as separate diagnostic categories.
Schizophrenia is now one diagnosis under the criteria in diagnostic manuals like the Diagnostic and Statistical Manual of Mental Disorders (DSM). The DSM, now in its 5th edition with a text revision (DSM-5-TR), is the primary clinical guidebook used in the United States and many other countries for mental health diagnoses.
Although the subtypes are no longer used formally, the names of the subtypes may be known to people diagnosed before the DSM-5-TR. These classic subtypes included:
- paranoid, with symptoms such as delusions, hallucinations, and disorganized speech
- hebephrenic or disorganized, with symptoms such as flat affect, speech disturbances, and disorganized thinking
- undifferentiated, with symptoms displaying behaviors applicable to more than one type
- residual, with symptoms that have lessened in intensity since a previous diagnosis
- catatonic, with symptoms of immobility, mutism, or stupor
Under current DSM-5-TR guidelines, all of the classic subtypes fall under the singular diagnosis of “schizophrenia.” If your doctor wants to add details about your symptoms to that diagnosis, they use one of the DSM-5-TR’s “specifiers,” diagnostic labels that provide insight into symptom patterns.
Specifiers for schizophrenia in the DSM-5-TR include:
- first episode, currently in acute episode
- first episode, currently in partial remission
- first episode, currently in full remission
- multiple episodes, currently in acute phase
- multiple episodes, currently in partial remission
- multiple episodes, currently in full remission
- continuous (symptoms remain for the majority of time)
- unspecified
- with catatonia
Your doctor can also assign severity specifiers to each symptom you experience on a scale of 0 to 4, with 4 representing the highest severity.
There’s no definitive test for schizophrenia. To receive a diagnosis, a medical doctor or a qualified mental health professional, like a psychiatrist or psychologist, takes a detailed history of your symptoms and behaviors and considers how they affect your daily life.
Many people living with schizophrenia delay seeking a diagnosis due to anosognosia, a lack of insight into the condition, and the inability to realize a mental health disorder is present.
If your doctor suspects schizophrenia, they can give an official diagnosis when two or more of the following DSM-5-TR criteria are present during a 1-month period.
At least one of your symptoms must be numbers 1, 2, or 3 on the list:
- delusions
- hallucinations
- disorganized speech (also known as disorganized thinking)
- grossly disorganized or catatonic behavior
- negative symptoms
Negative symptoms in schizophrenia are a category of emotional and behavioral experiences where there’s a significant loss of ability or function. They include:
- blunted affect: diminished emotional expression
- alogia: diminished speech
- avolition: reduced self-motivation
- anhedonia: inability to experience pleasure
- asociality: social withdrawal and disinterest
Research indicates that genetics is an important contributing factor to the development of schizophrenia. The exact cause of this disorder is unknown and appears to be complex. People who have relatives living with schizophrenia tend to have a higher risk.
Having an FDR living with schizophrenia is not a guarantee you’ll develop it. However, some people diagnosed with schizophrenia have no family history of the disorder. Environmental factors, substance use, and changes in the brain’s function or structure are other possible contributing factors.