Scientists are n't sure what 's behind the increase in earlier puberty . One theory is that excess body fat affects the levels of hormones that trigger puberty . Studies showed those who started smoking earlier at greater risk for certain diseases . Drugs : Chemicals such as bisphenol - A ( BPA ) may cause smoking .
Scientists are n't sure what 's behind the increase in earlier puberty . Studies showed those who started smoking earlier at greater risk for certain diseases . Drugs : Chemicals such as bisphenol - A ( BPA ) may cause smoking .