AP Psychology 5.3: Neurodevelopmental and Schizophrenic Spectrum Disorders

Schizophrenia

A psychotic disorder involving major disturbances in thought, perception, emotion, and behavior that substantially impair everyday functioning. It is not the same as dissociative identity disorder or “split personality.”

When does schizophrenia most commonly begin, and how prevalent is it?

It is usually first diagnosed in early adulthood, often during the early to mid-20s, although onset commonly falls roughly between ages 16 and 30. The OpenStax text estimates lifetime prevalence at about 1%.

What makes schizophrenia a psychotic disorder?

Psychosis involves thoughts, perceptions, or behaviors that are sufficiently impaired that the person becomes disconnected from consensual reality and has difficulty functioning normally.

How does schizophrenia affect daily functioning?

Many individuals experience substantial social and occupational impairment, including difficulty maintaining employment, managing finances, caring for themselves, and sustaining relationships. Some require repeated hospitalizations and continue to have serious impairment despite treatment.

Positive symptoms of schizophrenia

Symptoms that add unusual experiences or behaviors to normal functioning, including hallucinations, delusions, disorganized thinking, and disorganized or abnormal motor behavior.

Negative symptoms of schizophrenia

Symptoms involving noticeable reductions or absences of normal emotional expression, motivation, speech, pleasure, or social interest. Major examples include diminished emotional expression, avolition, alogia, asociality, and anhedonia.

Hallucination

A perceptual experience that occurs without corresponding external stimulation. Hallucinations may be auditory, visual, or olfactory.

Which type of hallucination is most common in schizophrenia?

Auditory hallucinations, such as hearing voices, are the most common; they occur in roughly two-thirds of patients according to the source. Visual and olfactory hallucinations are less common.

Delusion

A firmly held belief that contradicts reality and persists despite clear contradictory evidence. Delusions differ from merely unusual opinions because they are strongly maintained and clearly inconsistent with reality.

Paranoid delusion

A false belief that another person, group, or agency is plotting to harm, persecute, or kill the individual.

Grandiose delusion

A false belief that one possesses extraordinary power, unique knowledge, exceptional importance, or a special identity.

Thought withdrawal and thought insertion

Thought withdrawal is the delusional belief that one's thoughts are being removed. Thought insertion is the belief that thoughts have been placed into one's mind by an outside force.

Somatic delusion

A delusional belief that something highly abnormal is occurring in one's body, such as an implausible claim that internal organs are being destroyed.

Disorganized thinking in schizophrenia

Disorganized thinking consists of disjointed or incoherent thought processes, often revealed through speech. It may involve rambling, loose associations, illogical conclusions, or tangential responses.

Loose associations

A form of disorganized thinking in which a person's speech shifts abruptly from one topic to another with weak or unclear connections between ideas.

Tangentiality

A communication pattern in which a person responds to a question or statement with a remark that is only slightly related or unrelated rather than directly addressing the topic.

Disorganized or abnormal motor behavior

Unusual or poorly organized movements and behaviors, such as excessive activity, childlike behavior, purposeless repetition, or odd facial expressions and gestures.

Catatonic behavior

A severe disturbance in motor behavior marked by greatly reduced reactivity or unusual immobility. Examples include posturing—holding a rigid, bizarre position—and catatonic stupor, involving an almost complete lack of movement and speech.

Diminished emotional expression

A negative symptom characterized by little visible emotion in facial expressions, speech, or movements, even in situations where emotional expression would normally be expected.

Avolition

A lack of motivation to begin and sustain meaningful, self-directed activities, including basic self-care such as bathing or grooming.

Alogia

Reduced speech output; the person says very little or provides unusually brief responses.

Asociality

Social withdrawal or a markedly reduced interest in interacting with other people.

Anhedonia

A reduced or absent ability to experience pleasure, leading to little interest in activities such as hobbies, recreation, or sexual activity.

What evidence supports a genetic contribution to schizophrenia?

Risk increases with genetic relatedness to an affected family member, and having a parent with schizophrenia raises risk substantially—nearly sixfold in the cited source. However, genetic risk is not equivalent to genetic determinism.

Why can family and twin studies not completely prove that schizophrenia is genetic?

Closely related family members often share more similar environments, and identical twins may be treated more similarly than fraternal twins. Therefore, differences in schizophrenia rates could partly reflect shared experiences rather than genes alone.

How do adoption studies help clarify the causes of schizophrenia?

Adoption studies separate genetic relatedness from the rearing environment by examining children raised apart from their biological parents. Higher risk associated with biological relatives than adoptive relatives supports genetic influence, while environmental effects can still be evaluated.

What did adoption research suggest about genetic and environmental risk for schizophrenia?

Adoptees with high genetic risk were much more likely to develop schizophrenia or another psychotic disorder when raised in disturbed, highly critical, conflictual environments than when raised in healthy environments. This supports an interaction between vulnerability and environment.

Diathesis-stress model of schizophrenia

The disorder is understood as resulting from the interaction of an underlying vulnerability, or diathesis, with environmental stress. Genetic risk alone does not fully determine whether schizophrenia will develop.

What is the dopamine hypothesis of schizophrenia?

The classic hypothesis proposes that excessive dopamine activity or an excess of dopamine receptors contributes to schizophrenia. Evidence includes schizophrenia-like effects of dopamine-enhancing drugs and symptom reduction from dopamine-blocking medications.

How does dopamine dysregulation help explain different schizophrenia symptoms?

Excess dopamine activity in limbic regions has been linked primarily to positive symptoms such as hallucinations and delusions. Reduced dopamine activity in the prefrontal cortex has been associated with negative symptoms such as avolition, alogia, asociality, and anhedonia.

What role does serotonin play in schizophrenia treatment?

Serotonin abnormalities have also been implicated in schizophrenia. Some newer antipsychotic medications work partly by blocking serotonin receptors.

What brain-structure findings are associated with schizophrenia?

Many people with schizophrenia have enlarged ventricles, suggesting reduced surrounding brain tissue, along with reduced gray matter in the frontal lobes. Brain imaging also often shows lower frontal-lobe activity during cognitive tasks.

Why might frontal-lobe abnormalities contribute to schizophrenia symptoms?

The frontal lobes support planning, attention, speech, movement, problem solving, and other complex cognitive functions. Reduced frontal gray matter or activity could therefore help explain impairments in these abilities.

Which prenatal and birth factors have been associated with increased schizophrenia risk?

Reported associations include obstetric complications, maternal influenza during the first trimester, and severe maternal emotional stress during pregnancy, such as the death of a relative. These factors may disrupt normal fetal brain development but do not guarantee schizophrenia.

How is marijuana use related to schizophrenia risk?

Longitudinal evidence links marijuana use—especially frequent or early use—to increased risk of schizophrenia or other psychotic disorders and to earlier onset. Marijuana is neither necessary nor sufficient: many people with schizophrenia have not used it, and most users do not develop schizophrenia.

Why might early marijuana use increase later psychosis risk?

One proposed explanation is that marijuana may disrupt brain development during important periods of adolescent maturation, particularly in people who already have an underlying vulnerability.

Prodromal symptoms of schizophrenia

Early, relatively minor warning signs that may precede a psychotic disorder, including unusual thought content, suspiciousness or paranoia, odd communication, declining school or work performance, and reduced social functioning.

Which factors predict that a person with prodromal symptoms may develop a psychotic disorder?

Important predictors include a family history of psychosis, recent functional decline, unusual thought content, paranoia or suspiciousness, poor social functioning, and a history of substance abuse.

Why is research on prodromal symptoms clinically important?

Following people with early warning signs may improve prediction of who will develop schizophrenia and help direct early intervention to those at greatest risk.

How is schizophrenia typically diagnosed?

Diagnosis is based on observed behavior, the person's reported experiences, and information from people familiar with the individual's functioning. Clinicians must also consider other possible explanations, including substance use and mood disorders.