Dorret Boomsma: Using twins to gain insight into individual differences
‘Twin research makes it possible to study the association between observable characteristics - including impediments – and heridity. For that reason the Netherlands Twin Register is of great value, because research with twin families offers the option to study the impact of genetic difference between individuals on differences in health, cognition and personality.’
Dorret Boomsma is a biological psychologist who in a later stage of her MA education studied genetics in the United States. Nowadays she uses her knowledge in the study of behavior, in the broadest sense of the word. ‘We use IQ tests, observations, questionnaires and brain scanners.’ An important source of information for Boomsma is the Netherlands Twin Register, which she established at the Vrije Universiteit in the late 1980’s.
Boomsma and her colleagues established the twin register by collecting data of several thousands of twin pairs and their family members (parents, siblings, spouses). About four years ago the researchers started to add a biobank project, by collecting samples of blood and other biological materials of the twins and their family members. Currently the biobank contains data of over nine thousand twins and family members. ‘Over a period of three years, we visited all these volunteers at home, to maximize their participation.’
Because twin research can be applied widely, cooperation with other research groups of the Neuroscience Campus Amsterdam happens on regular base. ‘We have benefited greatly from collaborations with ongoing addiction studies. For example, we connected our knowledge of several polymorphisms, small DNA variations, associated with smoking to knowledge of Guus Smit about a cellular pathways. And we collaborated with the Netherlands Group on Depression Research. Together we identified a new gene for depression.’
Also, Boomsma adds, we have monozygotic twins in our database of which only one member has a depression. Such so-called ‘discordant twins’ are extremely informative for example in brain imaging studies. ‘We want to know if there is anatomical and functional difference between these genetically identical, but phenotypically different twins.’
Genetic factors
In the research field of attention and cognition, which Boomsma coordinates, cooperation takes place too. ‘In a number of projects we study the normal spectrum of attentional processes and cognition, and there are also projects focusing on ADHD. These show that genetic factors contribute siginificantly to the development of ADHD.
Not so long ago, a new branch was added to the twin research: epigenetic studies. Epigenetics refers to heritable processes that determine activity of DNA transcription and therefore the way we look and behave. ‘Our phenotype is determined by three factors: genetics, epigenetics and environment. Twin research can reveal the equilibrium between these three.’
