Describe the use of kinship studies to study the relationship between genes and behaviour.

Introduction to the approach

The biological approach argues that there are physiological origins of many behaviours and that human beings should be studied as biological systems. Biological approach studies behaviour as a result of genetic and other biological explanations.

Introduction to the topic

Modern biologists recognize the gene-environment interaction in the explanation of behavior. Epigenetics argues that in order for a behaviour to occur, genes must be “expressed.” One biological theory of depression is genetic inheritance. Genetic inheritance is the theory that abnormal behaviour, in this case, depression, can be passed down through genes. Genetic researchers argue that genetic predisposition can partly explain depression.

Introduction to the subtopic

Genetic studies look at concordance rates - that is, the degree to which traits between identical twins (MZ), fraternal twins (DZ), or siblings are similar. Twin studies are often used for this purpose, one of the largest studies to date, is by Kendler et al (2006). Twin studies uses sample of MZ and DZ twins as MZ share 100 % genes and DZ share 50% genes and then compare the difference in the concordance rates to draw conclusion.

Kendler el al (2006) - Aim

• Study type: Twin study using data from over 42,000 twins in the Swedish National Twin Registry.

• Aim: To determine the level of heritability of depression.

Kendler el al (2006) - Research Goals

1. Replication: To test whether previous findings on the heritability of major depression could be replicated in a large, representative twin sample.

2. Sex differences: To investigate whether genetic influences on depression differ by sex, specifically whether heritability is stronger in females than in males.

3. Cohort effects: To examine whether heritability varies across historical cohorts, testing the idea that heritability depends on population and time period, rather than being a fixed characteristic of the disorder.

Kendler el al (2006) - Method

Data collection was performed with a telephone interview by trained interviewers. Introductory letters describing the study were also sent to a random sample of which finally 42000 participants’ data was analysed. Informed verbal consent was obtained prior to the interview and it was approved by the ethics committee.

Kendler el al (2006) - Results

In this large, nationally representative twin sample the heritability of major depression was estimated to be 38%. These results are in close agreement to those obtained previously from a meta-analysis of the methodologically rigorous twin studies of major depression, which estimated, across studies, that heritability of major depression was 37%.

Link

Thus it was inferred from the study that MZ twins had a higher concordance rate as compared to DZ twins with females showing higher rates than men which supports the genetic hypothesis for depression using twin studies.

Conclusion

Thus, it can be concluded that human behaviour can be studied through the genetic make up that is shared amongst twins (100% MZ and 50% DZ) by conducting twin studies. This reiterates the principle that behaviour is inherited and correlations can be drawn between genes and behaviour through these studies.