Why do mood and behavioural disorders seem to run in families?
A large-scale Trust-funded study is helping to
show how parents' mental states are passed on to the next
generation, and to unravel the genetic and life events that cause
mood and behavioural disorders in children.
The Avon Longitudinal Study of
Parents and Children (ALSPAC) project, supported by the
Wellcome Trust and MRC since 2001, recruited around 14 000
expectant mothers in 1991. It has followed the development of their
offspring (now aged 18-19) ever since, collecting biological
samples and information about health and lifestyle.
Researchers at universities across the UK
mining the data discovered that children whose mothers experienced
high levels of anxiety during pregnancy are more likely to develop
asthma. This is likely to be an example of an epigenetic effect -
the stressful environment in the womb causing alterations to the
way genes are expressed in the fetus.
ALSPAC data also revealed that bullied
children are up to four times more likely to develop psychotic-like
symptoms such as hallucinations, delusions or paranoia - in
adolescence, for example. And boys whose fathers were depressed
both before and after they were born have an increased risk of
conduct problems in boys. The risk grows in proportion to the
duration of the father's depression.
A father's depression seems to have a specific
and lasting effect on his child's early development. However, it is
not clear is whether this is because the father's 'depressed' genes
are passed down to the child, or whether the baby's emotional
development is affected by the father's mood (an environmental
effect). There may also be an epigenetic effect before birth, if
the impact of the father's depression on the mother affects the
fetus in her womb.