Twins are a godsend for researchers interested in the nature / nurture debate. Two people, genetically very similar and brought up in the same environment. By studying twins where one develops a problem such as ADHD and the other doesn’t can give important clues to the causes and development of a problem.
A new study has looked at twins and ADHD, using the data from the Environmental Risk (E-Risk) Longitudinal Twin Study. The researchers from King’s College London and the University of Wisconsin-Madison asked three questions:
- Is ADHD caused by genes or environment?
- Are reading and behavior problems were linked to specific factors in the home environment?
- Do reading problems cause behavior problems, behaviour problems cause reading problems or neither?
The results where that genetics played only a small part in the development of ADHD (see Parenting and ADHD). Factors in the children’s home life such as child neglect, the mother’s reading skill, parental income, education and social class, deprivation, family size, maternal depression and/or young maternal age where all looked at as possible predictors of ADHD but no statistically significant results were found.
The third question, the link between reading and behavioral problems was different depending on the sex of the child. In boys reading and behavioral problems were linked. Having one problem appeared to cause to the other problem. But in girls, whilst behavioral problems caused reading problems, reading problems did not cause behavioral problems.
This evidence is really just telling us that reading and behavioral problems are incredibly complex and we shouldn’t assume anything about their development. It also worth noting these studies are correlational. They do not identify cause and effect, only an apparent link between factors. For an example of how this link can give rise to misleading conclusions, see how the global warming is caused the fall in pirates.