Smoking during pregnancy and high maternal stress hormones increase the risk for nicotine dependence in daughters, according to a new study.

The study, published in Biological Psychiatry, shows that exposure to stress hormones in the womb can predict nicotine use in female offspring. The research also backs up previous studies that suggest offspring born to mothers who smoked during pregnancy have a greater risk of nicotine addiction when they grow older.

While doctors already know that maternal smoking is a risk factor for dependence on nicotine, scientists do not understand the exact mechanism or pathway between maternal smoking and offspring dependence. Scientists had performed most of the previous research on animals, not humans.

This new study shows maternal smoking and high levels of maternal stress hormones deliver a one-two punch in terms of increasing the offspring’s ultimate risk for nicotine dependence. Mothers who smoke are more likely to be under a lot of stress and live in adverse conditions.

The study used data collected over 40 years. The national project began in 1959; researchers enrolled more than 50,000 mothers-to-be and followed the offspring for more than four decades.

In the new study, researchers focused their attention on 1,086 women who had their hormone levels checked and had stated their smoking status. Years later, scientists interviewed the 649 daughters and 437 sons of these participants to learn of their smoking status.

The scientists found that prenatal exposure to stress hormones and maternal smoking increased nicotine dependence in adult daughters. There was no evidence that exposure to other hormones, like testosterone, had the same effect. Furthermore, the effect was not evident in male offspring.

The researchers say they do not yet understand why the two genders react to maternal smoking and stress hormones differently but think that there are differences in the way the two genders regulate stress hormones. Additionally, nicotine and stress hormones may affect female and male brains differently. The scientists suggest further study to learn the mechanisms behind these events.

Source: Elsevier. "A daughter's risk of nicotine dependence increased by maternal stress hormones and maternal smoking." Medical News Today. MediLexicon, Intl., 14 Jan. 2014. Web. 20 Jan. 2014.