Study co-author Katri Räikkönen, from the University of Helsinki in Finland, and colleagues hypothesize that glycyrrhizin (the active ingredient in licorice) may interfere with fetal neurodevelopment by increasing levels of "the stress hormone" cortisol.
The researchers recently reported their findings in the American Journal of Epidemiology.
A study reported by Medical News Today in November, for example, associated licorice intake with reduced fertility for women, and studies have also suggested that licorice consumption during pregnancy may lead to poorer birth outcomes, such as a lower birth weight.
For this latest study, Räikkönen and team investigated how licorice intake during pregnancy might influence cognitive functioning and behavior in offspring.
The researchers explain that licorice's active ingredient, glycyrrhizin, is a strong inhibitor of placental 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2), which is an enzyme known to block the production of glucocorticoids such as cortisol.
As such, glycyrrhizin may increase glucocorticoid production, and research has suggested that prenatal exposure to excess glucocorticoids is associated with psychiatric illness.
Maternal licorice intake 'may harm the developing offspring'
To test this theory, Räikkönen and colleagues analyzed the data of 378 children, aged 13 on average, who were born in Helsinki, Finland, in 1998.
Data on the glycyrrhizin intake of the children's mothers during pregnancy were gathered. Low intake was defined as under 249 milligrams of glycyrrhizin per week, and high intake was defined as more than 500 milligrams of glycyrrhizin - the equivalent of around 250 grams of licorice.
The team used the Child Behavior Checklist to assess the presence of psychiatric problems among the children, and neuropsychological tests were used to evaluate their cognitive function.
Compared with children born to mothers who had a low intake of glycyrrhizin during pregnancy, those born to mothers with a high intake of glycyrrhizin showed poorer performance in memory tests.
Furthermore, children of mothers who consumed large amounts of glycyrrhizin during pregnancy were more likely to have behaviors associated with attention deficit hyperactivity disorder (ADHD).
Additionally, the researchers found that girls started puberty earlier if their mothers consumed high amounts of glycyrrhizin while pregnant.
Although further studies are needed in order to determine the precise mechanisms by which maternal glycyrrhizin intake might impact the cognition and behavior of offspring, the team speculates that glycyrrhizin blocks 11βHSD2, leading to an increase in cortisol - the so-called stress hormone. This can cause harm to the developing fetus.
Commenting on what their findings indicate, the researchers say that:
"Licorice consumption during pregnancy may be associated with harm for the developing offspring."
The team adds that expectant mothers should be warned about the possible harms of consuming products containing glycyrrhizin.