Schizophrenia is a devastating psychological disorder that is characterised by major disturbances in thought, perception, emotion and behaviour. About 1% of Canadians aged 10 and older are diagnosed with schizophrenia (Government of Canada, 2019). The disorder is commonly first diagnosed in young adulthood, with a significant number of new cases identified between the ages of 20 and 34, highlighting the critical period of early adulthood for the onset of this mental illness (Public Health Agency of Canada, 2019).

Most people with schizophrenia experience significant difficulties in many day-to-day activities, such as holding a job, paying bills, caring for oneself (grooming and hygiene), and maintaining relationships with others. Frequent hospitalisations are more often the rule rather than the exception with schizophrenia. Even when they receive the best treatments available, many with schizophrenia will continue to experience serious social and occupational impairment throughout their lives.

What is schizophrenia? First, schizophrenia is not a condition involving a split personality; that is, schizophrenia is not the same thing as dissociative identity disorder (better known as multiple personality disorder). These disorders are sometimes confused because the word schizophrenia, first coined by the Swiss psychiatrist Eugen Bleuler in 1911, derives from Greek words that refer to a “splitting” (schizo) of psychic functions (phrene) (Green, 2001).

Schizophrenia is considered a psychotic disorder, or one in which the person’s thoughts, perceptions and behaviours are impaired to the point where they are not able to function normally in life. In informal terms, one who suffers from a psychotic disorder (that is, has a psychosis) is disconnected from the world in which most of us live.

Symptoms of Schizophrenia

The main symptoms of schizophrenia include hallucinations, delusions, disorganised thinking, disorganised or abnormal motor behaviour, and negative symptoms (APA, 2013). A hallucination is a perceptual experience that occurs in the absence of external stimulation. Auditory hallucinations (hearing voices) occur in roughly two-thirds of patients with schizophrenia and are by far the most common form of hallucination (Andreasen, 1987). The voices may be familiar or unfamiliar, they may have a conversation or argue, or the voices may provide a running commentary on the person’s behaviour (Tsuang, Farone, & Green, 1999).

Less common are visual hallucinations (seeing things that are not there) and olfactory hallucinations (smelling odours that are not actually present).

Delusions are beliefs that are contrary to reality and are firmly held even in the face of contradictory evidence. Many of us hold beliefs that some would consider odd, but a delusion is easily identified because it is clearly absurd. A person with schizophrenia may believe that their mother is plotting with the FBI to poison their coffee, or that their neighbour is an enemy spy who wants to kill them. These kinds of delusions are known as paranoid delusions, which involve the (false) belief that other people or agencies are plotting to harm the person. People with schizophrenia also may hold grandiose delusions, beliefs that one holds special power, has unique knowledge, or is extremely important.

For example, the person who claims to be Cleopatra, or who claims to be a traveler, or claims to have a superpower, is experiencing grandiose delusions. Other delusions include the belief that one’s thoughts are being removed (thought withdrawal) or thoughts have been placed inside one’s head (thought insertion). Another type of delusion is somatic delusion, which is the belief that something highly abnormal is happening to one’s body (e.g., that one’s kidneys are being eaten by cockroaches).

Disorganised thinking refers to disjointed and incoherent thought processes, which are usually detected by what a person says. The person might ramble, exhibit loose associations (jump from topic to topic), or talk in a way that is so disorganised and incomprehensible that it seems as though the person is randomly combining words. Disorganised thinking is also exhibited by blatantly illogical remarks (e.g., “The CN Tower is in Toronto. I live in Toronto. Therefore, I live at the CN Tower.”) and by tangentiality — responding to others’ statements or questions with remarks that are either barely related or unrelated to what was said or asked. For example, if a person diagnosed with schizophrenia is asked if they are interested in receiving special job training, they might state that they once rode on a train somewhere. To a person with schizophrenia, the tangential (slightly related) connection between job training and riding a train are sufficient enough to cause such a response.

Disorganised or abnormal motor behaviour refers to unusual behaviours and movements: becoming unusually active, exhibiting silly child-like behaviours (giggling and self-absorbed smiling), engaging in repeated and purposeless movements, or displaying odd facial expressions and gestures. In some cases, the person will exhibit catatonic behaviours that show decreased reactivity to the environment, such as posturing, in which the person maintains a rigid and bizarre posture for long periods of time, or catatonic stupor, a complete lack of movement and verbal behaviour.

Negative symptoms are those that reflect noticeable decreases and absences of certain behaviours, emotions, or drives (Green, 2001). A person who exhibits diminished emotional expression shows no emotion in his facial expressions, speech or movements, even when such expressions are normal or expected. Avolition is characterised by a lack of motivation to engage in self-initiated and meaningful activity, including the most basic of tasks, such as bathing and grooming. Alogia refers to reduced speech output; in simple terms, patients do not say much. Another negative symptom is asociality, or social withdrawal and lack of interest in engaging in social interactions with others. A final negative symptom, anhedonia, refers to an inability to experience pleasure. One who exhibits anhedonia expresses little interest in what most people consider to be pleasurable activities, such as hobbies, recreation, or sexual activity.

Causes of Schizophrenia

There is considerable evidence suggesting that schizophrenia has a genetic basis. The risk of developing schizophrenia is nearly 6 times greater if one has a parent with schizophrenia than if one does not (Goldstein, Buka, Seidman, & Tsuang, 2010). Additionally, one’s risk of developing schizophrenia increases as genetic relatedness to family members diagnosed with schizophrenia increases (Gottesman, 2001).

Neurotransmitters

If we accept that schizophrenia is at least partly genetic in origin, as it seems to be, it makes sense that the next step should be to identify biological abnormalities commonly found in people with the disorder. The dopamine hypothesis of schizophrenia proposes that an overabundance of dopamine or too many dopamine receptors are responsible for the onset and maintenance of schizophrenia (Snyder, 1976). More recent work in this area suggests that abnormalities in dopamine vary by brain region and thus contribute to symptoms in unique ways. In general, this research has suggested that an overabundance of dopamine in the limbic system may be responsible for some symptoms, such as hallucinations and delusions, whereas low levels of dopamine in the prefrontal cortex might be responsible primarily for the negative symptoms (avolition, alogia, asociality and anhedonia) (Davis, Kahn, Ko, & Davidson, 1991).

Brain Anatomy

Brain imaging studies reveal that people with schizophrenia have enlarged ventricles, the cavities within the brain that contain cerebral spinal fluid (Green, 2001). In addition, many people with schizophrenia display a reduction in grey matter (cell bodies of neurons) in the frontal lobes (Lawrie & Abukmeil, 1998), and many show less frontal lobe activity when performing cognitive tasks (Buchsbaum et al., 1990). The frontal lobes are important in a variety of complex cognitive functions, such as planning and executing behaviour, attention, speech, movement, and problem solving. Hence, abnormalities in this region offer legitimate reasons why people with schizophrenia experience deficits in these areas.

Events During Pregnancy

Why do people with schizophrenia have these brain abnormalities? A number of environmental factors that could impact normal brain development might be at fault. High rates of obstetric complications in the births of children who later developed schizophrenia have been reported (Cannon, Jones, & Murray, 2002). In addition, people are at an increased risk for developing schizophrenia if the pregnant parent was exposed to influenza or experienced nutritional deficiencies or maternal stress during the first trimester of pregnancy (Brown et al., 2004; Brown, 2011; Fineberg et al., 2016; Pugliese et al., 2019).

Cannabis

Another variable that is linked to schizophrenia is cannabis (marijuana) use. A review of 35 longitudinal studies found a substantially increased risk of schizophrenia and other psychotic disorders in people who had used cannabis, with the greatest risk in the most frequent users (Moore et al., 2007). The National Institute on Drug Abuse (NIDA) highlights that considerable evidence, though not universally consistent, has linked cannabis use to an earlier onset of psychosis in individuals with genetic risk factors for psychotic disorders, including schizophrenia. Various factors, such as the amount of drug consumed, the frequency of use, the potency of the cannabis product, and the age at first use, play significant roles in influencing this relationship (National Institute on Drug Abuse, 2023). One plausible interpretation of the data is that early cannabis use may disrupt normal brain development during important early maturation periods in adolescence (Trezza, Cuomo, & Vanderschuren, 2008). Thus, early cannabis use may set the stage for the development of schizophrenia and other psychotic disorders, especially among individuals with an established vulnerability (Casadio et al., 2011).

Watch this video: Tricky Topics: Causes of Schizophrenia (9.5 minutes)

“Tricky Topics: Causes of Schizophrenia” video by FirstYearPsych Dalhousie is licensed under the Standard YouTube Licence.

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