evaluation

• one strength of the explanation for addiction genes is that there is supporting evidence from inheritance studies.
• inheritance studies - evidence

  Kendler and Prescott (1998) interviewed 2000 twins and found that although environmental and social factors would influence whether a person would initiate cocaine use, whether the person become addicted was more dependent on genetic factors.

  the concordance rate for cocaine initiation in MZ twins was 54% and 42% for DZ twins. However, the concordance rate for addiction maintenance to cocaine was 35% in MZ and 0% in DZ.
• inheritance studies - link

  higher concordance in MZ compared to DZ twins proves that a behaviour, like addiction, and the decision to initiate it, is majorly influenced by genetic factors.
• one weakness is that it relies on twin studies to support it.
• twin studies - explain

  twin studies assume high concordance rates are evidence of genetic causes of addiction.

  this doesn't account for confounding variables - perhaps MZ twins have higher concordance rates because people treat them more similarly than DZ twins? Reductionist.
• twin studies - example

  Jason Boardman et al. (2008) studied the rate of daily smoking in sibling and twin pairs, across all different schools in a sample.

  he found that the heritability rate was highest in the school where the most popular students were smokers, suggesting that the genetic predisposition to smoke was only expressed if influenced by social factors, such as peers.
• twin studies - link

  this methodological issue weakens the credibility of this explanation - reductionism.

  but just because the methods used are problematic, does not mean the underlying explanation is too.
• since the relationship between genes and addiction is complex, we cannot simply say there is one gene for addiction.
• genes and addiction - example

  as well as DRD2 and ADH genes, Ojelade et al. (2015) found that the Rsu1 gene was functioning incorrectly in fruit flies, it would lower their sensitivity to alcohol.

  brain imaging was then used to test for this in humans, finding a relationship between this and alcohol dependence.
• genes and addiction - explain

  some addiction genes are linked to other disorders too - the DRD2 gene is also found in people with autism and Tourette's, but people with these disorders are not pleasure seekers and do not tend to suffer from addictions.
• genes and addiction - link

  the link between genes and addiction is unclear.