Besides genetic susceptibility, environmental factors and gene-environment interactions are of central interest in research on attention deficit/hyperactivity disorder in children. Focusing on maternal behaviour during pregnancy, prenatal maternal alcohol consumption is associated with behavioural disorders in children. In animal models, developmental disorders of brain structures as well as subsequent behavioural disorders - similar to findings in attention deficit disorder - were caused by prenatal alcohol exposure. These findings occur in small rodents (mice, rats) as well as in primates and can be caused by even moderate alcohol exposure. In foetal alcohol syndrome (FAS) and foetal alcohol spectrum disease (FASD) in humans, symptoms like hyperactivity, disruptive or impulsive behaviour along with reduced attention and slower reaction time are observed. These findings resemble the symptoms of ADHD. For that reason, children diagnosed with FAS/FASD are frequently diagnosed with ADHD in parallel. Even small amounts of alcohol during pregnancy are responsible for cognitive and behavioural impairments like a significantly decreased IQ. About 50 % of adult ADHD patients show alcohol abuse or dependency and/or other substance disorders. Due to this, a higher rate of prenatal exposition to psychoactive substances for children of mothers affected with ADHD seems probable. However, there are no sufficient data on ADHD and its association to substance abuse in pregnancy, which makes it difficult to quantify the impact of genetic and environmental causes for the development of childhood ADHD. So far, no link could be proven with a high level of evidence between moderate prenatal alcohol consumption and the development of childhood ADHD. It has to be recognised that all present studies are based on self-reported alcohol consumption. Data collected by this methodology are usually severely biased to an underestimation of alcohol abuse. Objective tests for alcohol abuse in pregnancy, such as the analysis of fatty acid ethyl esters or ethyl glucuronide in foetal feces after birth, show rates of alcohol consumption in pregnant women which are dramatically higher than reported. Therefore, studies investigating the association between prenatal alcohol exposure and ADHD should incorporate the analysis and validation of more objective methods, such as parameters for alcohol degradation.
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