Explainer: What is puberty?

Puberty is a strange, exciting time. It kicks off adolescence — the body’s transformation from child to adult. 

All mammals go through some sort of puberty. In people, this period of life typically starts between age 8 and 15 and can last up to five or six years. During puberty, the body grows faster, changes shape and gets hair in new places. People born with a female anatomy will develop breasts and start their menstrual cycle. Those born with a male anatomy may notice their muscles enlarging and their voices deepening. Zits emerge. The body clock shifts, making it easier to stay up late and harder to wake early. Emotions surge. But they’re not all uncomfortable changes. At this stage in life, the brain gets better at complex tasks.

“It’s a massive period of change for the brain and for the whole endocrine system,” explains Megan Gunnar. She’s a psychologist at the University of Minnesota in Minneapolis. The endocrine system is made up of chemicals called hormones. Hormones direct a slew of activities in the body. They drive growth spurts. They help us respond to hunger pangs and then tell us when we’ve eaten enough. They even prepare our body for sleep.

Hormones also play a big role in puberty. They prompt the reproductive organs to mature. One hormone called estrogen equips female bodies to release eggs and nourish a developing fetus. In male bodies, this hormone fortifies sperm and keeps males fertile. Another hormone, testosterone, triggers the male body to develop masculine traits. It also promotes the growth of underarm hair.

Testosterone affects the brain, too, in ways that can influence how teens control their emotions. Emotional processing happens in a brain area called the limbic system. Another part of the brain known as the prefrontal cortex helps with decision-making. Sometimes that means putting a lid on harmful impulses and urges that arise from the limbic area.

Early in puberty, testosterone levels are low. At this point, kids tend to rely more on their limbic system. As testosterone levels rise with age, the prefrontal cortex becomes more active. That helps older teens regulate their emotions more like an adult. 

Hormones also equip us to handle daily and long-term stresses — such as high-stakes exams or divorce in the family. Research shows that these stress responses develop abnormally in kids who face trauma early in life — such as abuse or neglect. But according to recent studies by Gunnar and her coworkers, puberty also can be a time when these skewed stress responses reset to normal.