Schizophrenia

Definition and Classification of Schizophrenia

• Schizophrenia is a severe mental disorder that affects approximately $1\%$ of the global population, characterized by a profound disruption to cognition, emotion, and behavior.

• The disorder is classified using two major diagnostic systems:

  • DSM-5 (Diagnostic and Statistical Manual): Published by the American Psychiatric Association. It requires at least two core symptoms for a significant portion of a $1\,\text{month}$ period, with signs of disturbance lasting at least $6\,\text{months}$. One symptom must be delusions, hallucinations, or disorganized speech.

  • ICD-11 (International Classification of Diseases): Published by the World Health Organization.

Positive and Negative Symptoms of Schizophrenia

• Positive Symptoms (Type I): These represent an excess or distortion of normal functioning. They respond well to antipsychotic medication.

  • Hallucinations: False sensory perceptions without external stimulus. Auditory hallucinations (hearing voices) are most common; voices may comment, instruct, or converse. These are experienced as entirely real.

  • Delusions: Fixed, false beliefs held with absolute conviction despite contradictory evidence.

    • Persecutory delusions: Believing one is being harmed or spied upon.

    • Grandiose delusions: Inflated sense of power or importance.

    • Delusions of reference: Believing neutral events are personally directed at oneself.

• Negative Symptoms (Type II): These represent a diminution or absence of normal functioning. They are harder to treat and often require psychological intervention.

  • Speech poverty (alogia): Reduction in the quantity and quality of speech. Responses are brief or tangential, reflecting impoverished thought.

  • Avolition: Severe lack of motivation or goal-directed behavior, making basic activities like personal hygiene difficult. This reflects disrupted motivational systems rather than laziness.

  • Other examples: Affective flattening (reduced emotional expression) and anhedonia (inability to experience pleasure).

Reliability and Validity in Diagnosis

• Reliability (Consistency):

  • Test-retest reliability: Whether the same clinician gives the same diagnosis to the same patient on different occasions.

  • Inter-rater reliability: Whether different clinicians independently arrive at the same diagnosis for the same patient.

• Validity (Accuracy):

  • Predictive validity: Whether the diagnosis accurately predicts the course of the disorder and response to treatment.

  • Descriptive validity: Whether patients diagnosed share more in common with each other than with patients given other diagnoses.

• Key Threats to Reliability and Validity:

  • Co-morbidity: Schizophrenia frequently co-occurs with other disorders. Buckley et al. ($2009$) found approximately $50\%$ of those with schizophrenia also meet criteria for depression and $29\%$ for PTSD, making it difficult to establish as a distinct clinical category.

  • Symptom overlap: Hallucinations and delusions occur in bipolar disorder and severe depression; negative symptoms overlap with depression, threatening descriptive validity.

  • Culture bias: Cochrane ($1977$) found people of Afro-Caribbean origin in the UK were significantly more likely to be diagnosed than white British individuals. Spiritual beliefs may be misinterpreted as psychotic symptoms by Western-trained clinicians.

  • Gender bias: Castle et al. ($1993$) noted diagnostic criteria were developed using male samples. Women often show later onset and more affective symptoms, risking under-diagnosis or misdiagnosis.

Evaluation of Classification and Diagnosis

• Research Evidence - Inter-rater Reliability: Rosenhan ($1973$) showed $8$ healthy pseudo-patients were diagnosed with schizophrenia after reporting hearing a voice saying "thud," and were hospitalized for an average of $19\,\text{days}$ despite behaving normally. This demonstrates poor inter-rater reliability.

• Research Evidence - Consistency: Cheniaux et al. ($2009$) had two psychiatrists diagnose $100\,\text{patients}$. One diagnosed $26$ using DSM and $44$ using ICD; the other diagnosed $13$ and $24$ respectively. This reveals poor consistency between systems.

• Research Evidence - Predictive Validity: Mason et al. ($1997$) found modern systems show improved predictive validity regarding symptom progression and treatment response, suggesting the category retains clinical coherence.

• Applications: Awareness of unreliability led to the SCID (Structured Clinical Interview for DSM Disorders), providing standardized prompts to improve accuracy.

Biological Explanations for Schizophrenia

• Genetic Explanations: Schizophrenia is polygenic and multifactorial.

  • Family Studies: Gottesman ($1991$) found risk increases with genetic proximity: general population ($1\%$), one affected parent ($13\%$), two affected parents ($46\%$).

  • Twin Studies: Gottesman ($1991$) found MZ concordance of approximately $48\%$ versus $17\%$ for DZ twins.

  • Adoption Studies: Tienari et al. ($2004$) found adoptees with affected biological mothers had higher schizophrenia rates ($6.7\%$ vs $2\%$), even in different family environments.

• The Dopamine Hypothesis: Associated with dopamine dysregulation in the mesolimbic and mesocortical pathways.

  • Original Hypothesis (Carlsson \& Lindqvist, $1963$): Hyperdopaminergia (excess dopamine) in the mesolimbic pathway causes positive symptoms. Supported by typical antipsychotics blocking D2 receptors and amphetamines inducing psychosis-like states.

  • Revised Hypothesis (Davis et al., $1991$; Howes \& Murray, $2014$): Hyperdopaminergia in the subcortical mesolimbic pathway (positive symptoms) and hypodopaminergia in the prefrontal cortex mesocortical pathway (negative symptoms).

  • Abi-Dargham et al. ($2000$): Using PET scanning, found patients had significantly elevated baseline dopamine and greater release capacity in the striatum compared to controls.

• Neural Correlates (Structural Abnormalities):

  • Enlarged ventricles: Johnstone et al. ($1976$) showed patients had significantly larger cerebral ventricles (reduced brain tissue).

  • Hypofrontality: Reduced activity in the prefrontal cortex links to cognitive deficits and negative symptoms.

Evaluation of Biological Explanations

• Limitations of Genetics: MZ concordance of $48\%$ is not $100\%$, meaning a purely genetic account is an oversimplification. The Equal Environments Assumption (EEA) in twin studies may be violated as MZ twins are often treated more similarly than DZ twins.

• Limitations of Dopamine Hypothesis: It relies on pharmacological backwards reasoning (drug effects inferring causation). It is also reductionist, ignoring glutamate and serotonin. Atypical antipsychotics targeting serotonin often outperform dopamine-only drugs.

• Strength of Biological Research: It has led to genetic counseling and the development of antipsychotic medications, allowing many individuals to live independently.

• Implications: Biological accounts raise questions about determinism and personal responsibility in forensic contexts, though they can reduce the stigma of the disorder.

Psychological Explanations: Family Dysfunction and Cognitive Deficits

• Family Dysfunction:

  • Schizophrenogenic Mother (Fromm-Reichmann, $1948$): Described as cold, domineering, and rejecting, creating tension and mistrust.

  • Double Bind Theory (Bateson et al., $1956$): Children receiving contradictory messages (e.g., "I love you" with cold body language) learn their perception of reality cannot be trusted.

  • Expressed Emotion (EE): Level of critical comments, hostility, and emotional over-involvement. Vaughn and Leff ($1976$) found relapse rates of $51\%$ in high EE households vs $13\%$ in low EE.

  • Schism and Skew (Lidz et al., $1957$): Marital schism (chronic conflict) and marital skew (dominance by a pathological parent).

• Cognitive Explanations (Dysfunctional Thought Processing):

  • Metacognitive Deficits: Frith ($1992$) proposed impaired monitoring of mental processes. Patients struggle to distinguish internal thoughts from external events, explaining hallucinations and thought insertion.

  • Central Control Deficits: Deficit in suppressing automatic responses, leading to disorganized speech (word salads).

  • Executive Functioning: Deficits in working memory and selective attention. Leeson et al. ($2010$) linked memory impairments to an inability to filter irrelevant information.

  • Aberrant Salience: Attributing excessive significance to neutral stimuli, underlying delusions.

Evaluation of Psychological Explanations

• Research Support: Read et al. ($2005$) found a link between childhood abuse and schizophrenia. Leeson et al. ($2010$) supported cognitive models by identifying executive function impairments.

• Limitations: The causal direction of family dysfunction is unclear; having a family member with schizophrenia may cause the dysfunction. Cognitive accounts are reductionist as they describe symptoms without explaining the underlying biological origin (e.g., dopamine dysregulation).

• Symptoms Coverage: Both explanations struggle to account for negative symptoms like speech poverty and avolition.

• Applications: Research has driven Family Therapy and CBT, which improve quality of life and reduce hospitalizations.

Typical and Atypical Antipsychotic Drug Therapy

• Typical Antipsychotics (First-generation):

  • Mechanism: Dopamine antagonists that block D2 receptors in the mesolimbic pathway.

  • Example: Chlorpromazine (also has sedative effects via histamine receptors).

  • Evidence: Thornley et al. ($2003$) review found chlorpromazine significantly reduced symptoms versus placebo.

  • Side Effects: Tardive dyskinesia (involuntary movements), extrapyramidal effects (tremors), and sedation.

• Atypical Antipsychotics (Second-generation):

  • Mechanism: Block D2 dopamine and $5\text{-HT}_{2A}$ serotonin receptors. Serotonin antagonism increases dopamine in the prefrontal cortex, helping negative symptoms.

  • Examples:

    • Clozapine: Most effective for treatment-resistant cases; targets D4 and serotonin. Risks agranulocytosis (fatal white blood cell reduction), requiring blood monitoring.

    • Risperidone: Fewer severe side effects than clozapine. Bagnall et al. ($2003$) found it more effective than typicals.

  • Side Effects: Weight gain, metabolic syndrome, and type $2$ diabetes.

• Adams et al. ($2005$): Systematic review of chlorpromazine confirmed efficacy for positive symptoms but noted side effect drawbacks.

Evaluation of Drug Therapy

• Effectiveness: Typical antipsychotics are effective for positive symptoms ($60\%\,\text{response}$) but poor for negative symptoms ($16\%\,\text{response}$).

• Ethics: Informed consent is problematic during acute psychosis. Side effects like tardive dyskinesia reduced adherence.

• Suppression vs. Cure: Drugs manage symptoms rather than curing the disorder, as many patients relapse upon discontinuation.

• Societal Impact: Antipsychotics enabled deinstitutionalization, shifting care from hospitals to the community.

Psychological Treatments and Management

• Cognitive Behavior Therapy (CBT):

  • Techniques: ABCDE framework (Activating event, Beliefs, Consequences, Disputing, Restructuring), identifying the origin of voices, and coping strategy enhancement.

  • Aim: Reduce distress, not necessarily eliminate symptoms.

  • Evidence: Tarrier et al. ($2004$) found CBT combined with medication reduced hallucination frequency more than medication alone.

• Family Therapy:

  • Components: Psychoeducation, improving active listening, problem-solving, and setting realistic expectations.

  • Evidence: Pharoah et al. ($2010$) meta-analysis showed reduced relapse and hospitalization.

• Token Economies (Management Strategy):

  • Mechanism: Operant conditioning using positive reinforcement. Tokens (secondary reinforcers) are given for target behaviors (hygiene, social activity) and exchanged for rewards (primary reinforcers).

  • Limitation: Mixed evidence; gains often do not generalize beyond institutional settings. Ethical concerns exist regarding the manipulation of vulnerable patients' basic needs.

The Interactionist Approach and the Diathesis-Stress Model

• Interactionist Approach: Schizophrenia results from the interaction of biological, psychological, and social factors. Treatment typically combines medication with therapies (e.g., CBT).

• Diathesis-Stress Model:

  • Diathesis (Vulnerability):

    • Genetic: Original focus.

    • Neurodevelopmental: Read ($2001$) proposed early trauma alters brain development. Cannon ($2002$) linked birth complications (oxygen deprivation) to risk.

    • Psychological: Early trauma reduces the individual's threshold (Ingram \& Luxton, $2005$).

  • Stress (Trigger): Activation of vulnerability via stressors like heavy cannabis use in adolescence, urban living, discrimination, or high EE.

• Evaluation:

  • Support: Tarrier et al. ($2004$) showed biological and psychological treatments work synergistically. Twin studies (MZ concordance < $100\%$) prove stressors are necessary to trigger genetic vulnerability.

  • Limitations: The model is difficult to test empirically or operationalize; "diathesis" can become too broad (all early adversity), reducing predictive precision.

  • Implications: Supports soft determinism, reducing stigma by showing individuals are not just their genes and that environment-based prevention and recovery are possible.