Passing ADHD from one generation to the next.

Prenatal and early postnatal exposure of the developing brain to nicotine (PNE) is a major risk factor for inducing attention deficit hyperactivity disorder (ADHD). Children born to mothers who smoke cigarettes before, during, or immediately after pregnancy have a twofold higher risk of developing ADHD. Zhu et al. show that hyperactivity and attention deficits induced by putting nicotine in the drinking water of pregnant mice is transmitted from one generation to the next via the maternal but not the paternal line of descent. The authors note:

A plausible mechanism for the transgenerational transmission of the PNE-induced brain and behavioral changes is heritable epigenetic modifications of the germ cell genome. Nicotine is known to produce DNA methylation in a number of genes, including the gene coding for monoamine oxidase, a key enzyme in the metabolism of dopamine and other monoamines.