Biological explanations

Biological explanations focus on internal physical factors that may contribute to schizophrenia, such as inherited traits, chemical imbalances, or brain structure differences. These approaches suggest that the disorder arises from physiological processes rather than external influences alone.

Genetic explanations

Genetic explanations propose that schizophrenia can be inherited, with the risk increasing based on how closely related someone is to an affected individual. Research often compares concordance rates, which measure the likelihood that both individuals in a pair develop the disorder.

Evidence from twin and family studies:

• Gottesman (1991) analysed around 40 twin studies, revealing a concordance rate of approximately 48% for monozygotic (MZ) twins, who share all their genes, compared to about 17% for dizygotic (DZ) twins, who share half their genes.
• Shields (1962) examined MZ twins raised in different homes, finding a concordance rate close to 50%, indicating a strong genetic influence independent of shared upbringing.
• Adoption studies show that individuals adopted away from their biological families are more prone to schizophrenia if a biological parent has the disorder.

Limitations of genetic explanations:

• Concordance rates for MZ twins never reach 100%, suggesting that genetics alone cannot account for the disorder.
• Higher rates in families might result from shared environments, where behaviours are learned through observation rather than inherited.
• These findings highlight the need to consider environmental influences alongside genetic factors.

Biochemical explanations

Biochemical explanations centre on imbalances in brain chemicals, particularly dopamine. The dopamine hypothesis suggests that excessive activity at dopamine synapses contributes to schizophrenia symptoms.

Evidence supporting biochemical explanations:

• Brain imaging techniques, such as PET scans, and post-mortem examinations reveal elevated dopamine levels in individuals with schizophrenia.
• Medications that block dopamine receptors, known as antipsychotics, often alleviate symptoms, supporting the idea of overactive dopamine pathways.
• Substances like amphetamines, which boost dopamine activity, can induce symptoms resembling schizophrenia in those without the disorder.

Limitations of biochemical explanations:

• Antipsychotics primarily address positive symptoms, such as hallucinations, but are less effective against negative symptoms like emotional flatness.
• The association between dopamine and schizophrenia is correlational, meaning high dopamine might be an outcome of the disorder rather than its origin.

Neurological explanations

Neurological explanations link schizophrenia to unusual brain structures or functions, often identified through imaging. Neural correlates refer to brain features associated with specific conditions or behaviours.

Evidence supporting neurological explanations:

• Johnstone et al. (1976) used brain scans to identify enlarged ventricles in people with schizophrenia, potentially linked to decreased volume in areas like the temporal and frontal lobes.
• Buchsbaum (1990) employed MRI scans and observed abnormalities in the prefrontal cortex among those with schizophrenia, suggesting these structural differences contribute to the disorder.

Limitations of neurological explanations:

• Enlarged ventricles appear in some individuals without schizophrenia, weakening the direct causal link.
• Such brain differences are correlational and could emerge as a result of the disorder rather than causing it.

Evolutionary explanations

Evolutionary explanations argue that schizophrenia persists in the population because it once provided survival benefits. Traits associated with the disorder might have been advantageous in ancestral environments, such as enabling group leadership or innovation.

Key ideas in evolutionary explanations:

• Individuals with schizophrenia may exhibit qualities similar to ancient shamans, who were valued for their unique perceptions and could guide group divisions when populations grew too large, fostering new communities.
• The persistence of schizophrenia genes implies some evolutionary advantage, as disadvantageous traits would typically be selected against.

Evidence supporting evolutionary explanations:

• The consistent genetic component of schizophrenia across populations suggests it must have conferred benefits in human history to avoid being eliminated through natural selection.

Limitations of evolutionary explanations:

• Supporting evidence is scarce and challenging to verify empirically.
• The theory lacks widespread acceptance and is often viewed as speculative.

Psychological explanations

Psychological explanations emphasise mental processes and family dynamics as potential causes of schizophrenia. These approaches consider how thought patterns or interpersonal relationships might contribute to the development of symptoms.

Family dysfunction explanations

Family dysfunction theories suggest that problematic family environments can trigger schizophrenia, particularly through communication issues or emotional stress.

Key concepts in family dysfunction:

• The concept of a 'schizophrenogenic' mother describes a domineering and emotionally cold parent who creates tension leading to the disorder.
• Bateson (1956) proposed the double bind theory, where conflicting messages from family members cause confusion and contribute to schizophrenia.
• High expressed emotion (EE) environments, characterised by criticism and hostility, are linked to higher relapse rates.

Research on family dysfunction:

• Vaughn and Leff (1976) studied individuals with schizophrenia after hospital discharge, comparing those returning to high-EE versus low-EE homes. Relapse was more common in high-EE settings.
• Lidz et al. (1958) identified patterns like distant parenting and imbalanced marriages in families of those with schizophrenia, but these studies are criticised for being retrospective and potentially blaming families unjustly.

Limitations of family dysfunction explanations:

• They overlook biological evidence and may unfairly attribute causation to families.
• Methodological issues, such as relying on after-the-fact reports, mean the disorder itself might have caused family strain.
• Most children from dysfunctional families do not develop schizophrenia, indicating other factors are involved.

Cognitive explanations

Cognitive explanations attribute schizophrenia to faulty thinking processes, which impair perception, memory, and reasoning, leading to symptoms like delusions.

Evidence supporting cognitive explanations:

• Neufeld (1978) tested stimulus encoding and found that people with schizophrenia took longer to process information and displayed short-term recall difficulties.
• Meyer-Lindenberg et al. (2002) observed reduced brain activity during memory and reasoning tasks in those with schizophrenia, correlating with poorer performance.

Limitations of cognitive explanations:

• Cognitive deficits might stem from biological issues, like dopamine imbalances, making them effects rather than causes.
• These explanations overlap with other disorders and require integration with biological models for a complete understanding.

Socio-cultural explanations

Socio-cultural explanations link schizophrenia to societal pressures, particularly those affecting marginalised groups. The social causation hypothesis posits that stressors from low socio-economic status increase vulnerability.

Harrison et al. (2001) found higher rates of schizophrenia among people born in economically disadvantaged areas, suggesting poverty and discrimination elevate stress levels that may trigger the disorder.

Limitations of socio-cultural explanations:

• Findings are correlational, not proving causation; stress might not directly cause schizophrenia.
• The social drift hypothesis counters this by suggesting that schizophrenia leads to downward social mobility, resulting in individuals ending up in deprived areas rather than the reverse.

The diathesis-stress model

The diathesis-stress model integrates biological and environmental factors, offering an interactionist perspective that avoids the reductionism of purely biological views. It proposes that inherent vulnerabilities combine with life stressors to produce schizophrenia.

Key components of the diathesis-stress model:

• Diathesis refers to biological predispositions, such as genetic risks or biochemical imbalances.
• Stress encompasses environmental triggers, including work pressures, family conflicts, or financial strain.
• The model explains why not everyone with genetic risks develops schizophrenia—stressors are needed to activate the vulnerability.

Strengths of the diathesis-stress model:

• It accounts for the interplay between nature and nurture, supported by evidence that biological factors alone do not guarantee the disorder.
• This approach is holistic, recognising multiple influences rather than a single cause.