BIOLOGICAL EXPLANATIONS

~Inheritance~

• Evidence in favour of a genetic link, comes from family studies which indicate that the closer the genetic relationship to someone with SZ, the greater the chance of developing the disorder

• Gottesman (1991) conducted a large-scale family study: he found that individuals with an identical twin who suffers from SZ have a 48% risk of being diagnosed with the disorder. He also found that siblings have a 9% concordance rate

~Candidate Genes~

• SZ is polygenic (involves multiple genes) e.g. COMT - affects the breakdown of dopamine in the brain which can lead to excess dopamine in the prefrontal cortex leading to delusions and hallucinations

• SZ is aetiologically heterogenous (meaning that different combinations of genes can lead to the condition)

• Ripke et al (2014) found that 108 separate genetic variations were associated with an increased risk of SZ

EVALUATION

Research Support:

→ SUPPORTING EVIDENCE FROM ADOPTION STUDIES

• One strength is that evidence for the genetic basis of SZ also comes from adoption studies.

• For example, Tienari et al (2004) studied 164 adoptees with schizophrenic biological mothers and 197 control adoptees with non-schizophrenic biological mothers. They found that 6.7% of the adoptees with schizophrenic biological mothers went on to develop the disorder themselves, compared to just 2% of the control adoptees.

• A recent study by Hilker et al (2018) showed a concordance rate of 33% for MZ twins and 7% for DZ twins, supporting the argument for a genetic basis for SZ.

• It suggests that, regardless of whether an individual is raised in the family home or not, having a biological relative with the disorder increases risk.

→ REAL-WORLD APPLICATION

• Another strength of the genetic explanation is its real-world application in genetic counselling.

• As our understanding of the genetic basis of SZ improves, genetic counselling is becoming more widespread. This helps potential parents with a family history of SZ understand their recurrence risk - the likelihood of passing on the condition.

• This can aid in making informed decisions about family planning and early intervention strategies.

• The ability to offer guidance based on genetic risk highlights a valuable practical benefit of the genetic explanation.