Investigating the genetic building blocks of emotion and behaviour in the general population

In the past decade it has become apparent that genes play an important role in
the aetiology of emotional and behavioural problems. To date linkage and
association studies have identified several candidate genes that have a small
to moderate effect on emotion and behaviour. There now is compelling evidence
that genes such as; BDNF, 5-HTTLPR, DAOA, G72, DTNBP1, NRG1 and COMT influence
emotions and behaviour. However, as with many complex traits the contribution
of these genes to the trait is modest to small. This effect is aggravated by
the complexity of emotions and behaviour. Some of these candidate genes have
been identified in subjects with a broad variety of dysfunctions in the
cognitive and social domains. Consequently it is unclear to what emotions or
behaviour traits these genes are associated. Investigating the contribution of
single genes to emotional and behavioural traits will greatly facilitate the
unravelling of the genetic influence on emotion and behaviour.

This study aims to identify the relationship between candidate genes such as
for instance BDNF, 5-HTTLPR, DAOA, G72, DTNBP1, NRG1 and COMT with cognitive
function and emotional- and behavioural traits.

A cross sectional study will be conduced where detailed behavioural data will
be related to selected genotypes. Subjects will be selected based on genotype
information from available samples. Next, selected subjects will be reassessed
with regard to behavioural characteristics. From the 6000 samples we will
include subjects homozygous for variants of genes that are associated with
emotion or behaviour an equal amount of subjects homozygous for the other
allele. Thus we would end up with a total number of fourteen groups, twice the
number of candidate genes, adding up to a total of maximum 1050 subjects. After
secondary informed consent we will asses psychological, cognitive and social
functioning of these subjects. Raters and participants will remain blind for
the genotype status in order to avoid rater bias and ethical complications.
Blood samples will be taken to investigate RNA expression of the subjects.

The burden for the volunteers is modest. Most of the questionnaires can be done
via the internet, in the desired tempo and place of the volunteers. The
remaining questionnaires and assessments can be done in less than two hours.
For this part of the research a rater will visit the subjects at home or the
subjects can visit the local health centre. Obtaining a blood sample is a
minor procedure which shall be preformed by an experienced medical doctor.