SZ explanations

Neurotransmitter (biological), Social Causation, Genetics (bio??)

What is the heritability of schizophrenia according to Hillier et al. (2008)?

The heritability of SZ may be 79%, suggesting a very significant role for genetic factors in its causation.

What did Gottesman's family study suggest about genetic similarity and schizophrenia risk?

There is a strong correlation: the more closely related two individuals are, the greater the chance they will both have schizophrenia, indicating that SZ runs in families.

What is a limitation of twin studies in genetics research?

Monozygotic (MZ) twins share 100% of their DNA and are likely to have similar environments, making it difficult to separate genetic from environmental influences.

How does the C4 gene relate to schizophrenia as per Sekar et al. (2015)?

A specific form of the C4 gene is linked to excessive synaptic pruning during adolescence, potentially leading to a thinner cerebral cortex and the emergence of SZ symptoms in late adolescence/early adulthood.

What environmental factor increases the risk of schizophrenia according to Pedersen & Mortensen (2006)?

The longer a person lives in a city and the denser the urban population, the greater their risk of developing schizophrenia, indicating the environment can trigger a genetic predisposition.

What is the function of the COMT gene?

It provides instructions for creating an enzyme that breaks down dopamine in the prefrontal cortex; deletion of this gene leads to poorly regulated dopamine levels and increased SZ risk.

What did Egan et al. (2008) find about the COMT "Val" allele?

Inheriting two copies of the "Val" allele increases the risk of SZ by 50%, which demonstrates how specific genetic variations can predispose someone to the disorder.

What is the Diathesis-Stress Model related to schizophrenia?

It proposes that genes create a vulnerability (diathesis) for SZ, but the disorder is only triggered when combined with environmental stressors, such as cannabis use.

What is a key application of genetic research for families affected by schizophrenia?

Genetic counseling can calculate recurrence risk, help families interpret information, reduce fears of inevitability, and support rational family planning decisions.

What is a major challenge in identifying specific

schizophrenia genes? It is a polygenic disorder, with estimates suggesting links to up to 700 genes, but recent studies indicate a subset of around 120 genes involved, highlighting its complex genetic nature.

What is the core claim of the Social Causation explanation of schizophrenia?

Factors in a person's social environment (e.g., poverty, stress, discrimination) are a major cause in triggering schizophrenia, especially in vulnerable individuals.

How does 'Social Adversity' increase the risk of schizophrenia?

Growing up in unfavourable environments (poverty, unemployment) creates chronic stress, preventing access to treatment and increasing vulnerability to mental health disorders.

What is 'Urbanicity' and its relation to schizophrenia risk?

Urbanicity refers to urban living; individuals in the most urban environments have a 2.37 times higher risk of schizophrenia compared to those in rural areas.

What is the 'Social Drift Hypothesis'?

Proposed by David Matza, it suggests that schizophrenia causes individuals to drift into poverty and inner-city areas, implying that correlation does not equal causation.

What is 'Social Defeat' and its biological link to schizophrenia?

Chronic Social Defeat, or prolonged social exclusion, is linked to increased dopamine activity, which may explain how social stress leads to schizophrenia symptoms.

How does 'Social Isolation' contribute to schizophrenia development?

Social isolation can lead individuals to withdraw and cut off from feedback, allowing 'strange' thought patterns to develop without challenge.

How do immigration and minority status increase schizophrenia risk?

Immigrants, especially second-generation, may experience higher risks due to prejudice, discrimination, and chronic social stress.

What did Veling (2010) find regarding ethnic identity as a protective factor?

Individuals with a strong ethnic identity (Integrated or Separated) had a lower risk of schizophrenia compared to those with weak ethnic identities (Marginalized or Assimilated).

How does Tienari's (1994) study support the environmental role in schizophrenia?

In adopted children with a biological mother with schizophrenia, the disorder manifested only in maladaptive environments, highlighting the need for an environmental trigger.

What is the main limitation of the social causation explanation?

It often correlates rather than demonstrates causation and overlooks genetic factors; the Diathesis-Stress model presents a more comprehensive view.

What is the core claim of the original Dopamine Hypothesis?

Hyperdopaminergia – an excess of dopamine activity in the mesolimbic pathway is linked to the positive symptoms of schizophrenia.

What is the revised version of the Dopamine Hypothesis?

It involves both hyperdopaminergia in the mesolimbic pathway causing positive symptoms and hypodopaminergia in the mesocortical pathway causing negative symptoms.

What is a key strength of the dopamine hypothesis from drug studies?

Amphetamines can aggravate positive symptoms or induce psychosis, while antipsychotics are effective in reducing positive symptoms.

How does Depatie & Lal (2001) challenge the dopamine hypothesis?

They found that apomorphine did not induce psychotic symptoms in non-psychotic individuals or worsen symptoms in those with schizophrenia.

What is the role of Glutamate in alternative explanations?

Glutamate deficiency at NMDA receptors is proposed as a primary cause of schizophrenia, with low glutamate leading to dopamine dysregulation.

What is the 'Accelerator and Brake' model involving dopamine and glutamate?

Dopamine is the accelerator for psychosis, while glutamate is the brake; low glutamate fails to inhibit dopamine, causing positive symptoms.

How does the effectiveness of Clozapine challenge the original dopamine hypothesis?

Clozapine is effective despite weak binding to D2 receptors, indicating the role of serotonin and other neurotransmitters in schizophrenia.

What is the 'Aberrant Salience' model proposed by Howes and Kapur (2009)?

It suggests that dopamine dysregulation makes neutral stimuli feel unusually important, leading to the formation of delusions.

What is a major weakness of most evidence for neurochemical explanations?

The evidence is largely correlational and does not prove causation.

How do findings from immigrant studies challenge a purely biological explanation?

Velling et al. (2008) found that Moroccan immigrants had a higher likelihood of schizophrenia diagnosis than Turkish immigrants, correlated with levels of discrimination.

What is the modern, interactionist conclusion about neurotransmitters and schizophrenia?

Dopamine dysregulation is now viewed as the final common pathway to psychosis, influenced by a combination of genetic, environmental, and social factors.