Eight-year-olds now wear bras. For many girls in the developed world, puberty is coming earlier than ever before, with studies showing that, on average, puberty is now starting for girls at around 10 years old - at least five years earlier than a century ago. There are several explanations for this, but research is now revealing a worrying side effect of the trend - early puberty seems to also increase the risk of health problems later in life, such as increased rate of breast cancer, heart disease, and depression, as Julie Beck reported for The Atlantic this week. In other words, the hormonal changes associated with triggering early maturation seem to impact women long after puberty ends in ways we're only now beginning to understand. But what's going on here from a scientific point of view? The idea that girls are reaching sexual adolescence earlier than ever before is nothing new - for years, researchers have noticed that women are getting their periods earlier and earlier - the