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Schizophrenia: Symptoms, Causes & Treatment

Instructor: Tiffany Frye
Schizophrenia is a complex psychological disorder that affects approximately 0.7 percent of the world population. Explore the defining characteristics of the disorder, its positive and negative symptoms, contributing causes, and common treatments. Updated: 02/05/2022

Schizophrenia: A Split Mind

Artistic rendering of a patient

Schizophrenia is a serious mental illness usually recognized by disorganized thinking, delusions, hallucinations and a lack of normal affect. The word schizophrenia comes from two Greek words meaning 'split' and 'mind.' Because of this, schizophrenia is often confused with multiple personality disorder, in which patients assume two or more differing identities, splitting their personalities. Instead, the split mind of schizophrenia refers to the splitting of mental functions from an organized whole into incoherent parts.

The World Health Organization reported in 2012 that schizophrenia had a global prevalence of 0.7% and that 50% of people with schizophrenia were not receiving adequate treatment.

Positive Symptoms

When you hear 'positive,' you may think this means something good. Unfortunately, that is not the case when talking about schizophrenia. The word positive in the context of schizophrenia means the presence of symptoms or behaviors that are absent in someone without schizophrenia. Because they are not present in individuals with normal psychological health, hallucinations and delusions are considered positive symptoms of schizophrenia.

Patients with schizophrenia often have auditory hallucinations, during which they hear things that other people do not hear. These voices may provide a running commentary on the individual's life or they may instruct him or her to do certain things. Patients with schizophrenia may also see things that other people do not see; these are visual hallucinations.

Delusional thinking is also a common symptom. Delusional thoughts are defined as those that defy normal reasoning and that patients firmly adhere to even in the face of contradictory evidence. Examples of delusions include beliefs that one is being persecuted or pursued and an inflated sense of self-worth that causes a patient to believe that he or she has special powers or gifts beyond the scope of reason.

The actor Russell Crowe famously portrayed delusional thinking and hallucinations in his role as John Nash in the movie A Beautiful Mind. In this movie, John Nash develops a subtype of schizophrenia known as paranoid schizophrenia, which is most commonly identified by the presence of hallucinations and delusions.

John Nash
Photograph of John Nash

Negative Symptoms

As you may have guessed, negative in this context does not simply mean bad. It refers to characteristics that a normal healthy individual has but that are absent in a schizophrenic patient.

You might find it difficult to imagine not laughing at a funny movie or crying at a sad one or having no interest in spending time with friends, but these are common experiences of a patient with schizophrenia. In addition to diminished emotional response and a lack of motivation to have social relationships, negative symptoms also include diminished speech and movement and an inability to experience pleasure. As you can see, as opposed to hallucinations and delusions, these negative symptoms represent a lack of things that most people are able and happy to do.

Negative symptoms are often seen in the subtype known as disorganized schizophrenia, in which a patient has inappropriate emotional responses and confused thinking and speech. They are also seen in the rare subtype of schizophrenia known as catatonic schizophrenia, during which patients may cease to move altogether or only exhibit abnormal postures and movements.

Causes and Etiology

Schizophrenia is a complex disorder and there is no simple answer to the question of what causes it. However, the predominating view is known as the stress-vulnerability model and postulates that schizophrenia is caused by a combination of inherited vulnerabilities, environmental factors and life stressors.

Genetic studies have shown schizophrenia to be highly heritable, meaning that someone with a family history of schizophrenia or other mental illness is more likely to develop the illness than someone with no such history. One of the most convincing pieces of evidence for genetic predisposition comes from twin studies. Monozygotic, or identical, twins have the same genetic make-up. If one identical twin develops schizophrenia, the other could have up to a 40% chance of also developing the disorder. In contrast, dizygotic, or fraternal, twins, do not share as much genetic material and correspondingly do not share the same risk for developing schizophrenia.

Other factors postulated to play a part in the development of schizophrenia include prenatal complications, low oxygen levels at birth, viral infection, cannabis use, living in urban areas and socioeconomic hardship and social isolation during childhood.

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