If your teenager is moody, they really can blame changing hormones. For the first time scientists have identified a hormone that switches from soothing to stressful during puberty. This ScienCentral News video has more.
Stressed Out Teens
14-year-old Ashley Chapin goes through the stresses of a regular teenager: feeling the peer pressure about what to wear, how to dress, how to do her hair. She has a great relationship with her mom, but admits it sometimes gets ugly. "We're at the store, right, and we're shopping around. And I'm looking at some black stuff, and she sees this skirt that she wants me to buy. And I'm like 'Oh my god, it's pink, I don't want to buy it,'" she says.
Luckily her mom, neuroscientist Sheryl Smith, is an expert on teenage mood swings. She discovered that in female mice going through puberty, a hormone called THP that normally calms nerve cells, excites them instead.
THP, tetrahydroprogesterone, is a steroid that's derived from progesterone, a familiar hormone that has multiple effects in the reproductive and nervous systems, among others. Smith studied the effects of THP produced in the brain, and up to this time, THP has been seen as a stress-reducer. "It's released during stress," she says, "so it's believed that one of its functions is to help you calm down after a period of stress." Smith says that in high enough doses in adults, THP has been shown to work as a tranquilizer and anesthetic.
THP targets a specific brain receptor -- one of the GABA receptors, which respond to alcohol, tranquilizers, and sedatives. She found that by recreating this specific GABA receptor in a lab dish, she could test how mouse brain receptors would react to THP. She also conducted experiments with human brain receptors, piecing together the receptors using DNA. "We found that the target in the brain, which helps the nerve cells calm down, was somewhat different at puberty, it changed," she says. "We found that this target [at puberty] responded in the opposite way to THP."
After being exposed to a mild stress, mice going through puberty avoided the open arms of this elevated platform, meaning that they had continued anxiety.
To test this beyond the lab dish, they used mice on an elevated platform. Called an "elevated plus maze," the lab setup consists of two open, exposed arms and two arms surrounded by walls. After containing the mice in a Plexiglass container, which induced some mild stress in the mice, the researchers waited 20 minutes to make sure that THP kicked in. The mice going through puberty were more anxious and avoided the platform's open arms.
But as Smith wrote in the journal Nature Neuroscience, pubescent mice engineered not to respond to THP did not become anxious in this experiment, and explored more. In other experiments, Smith blocked THP itself to verify this effect. "We were then able to prevent formation of THP, which you can do with another chemical, and we did not see the increase in anxiety," she says. "So it suggested to us that at puberty, this stress steroid actually has the opposite effect and that you could really explain why you might expect to see a mood swing or a more exaggerated response to stress."
She says that mice and people share the same hormonal changes and that this work could have implications for treating severe mood disorders. "I think that the fact that we've identified the steroid could lead to therapies for teenagers who have increased anxiety or depression and be in search of a therapy," she says. "I think that it's because we've identified the mutations that could prevent it, there's even possibly a long-term goal of at some point for gene therapy. But again these would only be warranted if there were extreme reactions to puberty and mood swings."
Teenager Ashley Chapin (left) and her mother Sheryl Smith (right) have a great relationship, but disagree on some issues, like clothing.
Smith says that parents should seek therapy for children with extreme or abnormally increased anxiety or depression. But for most teens, mood swings are just a normal part of growing up. "I think the best advice would be just to be understanding about the teenager who's going through a mood swing or maybe gets angry or withdrawn, that they may be having more stress than the adult realizes," she says. "Teenagers who have mood swings or changes in personality are not doing it to be frustrating to their parents, there's actually a biological basis for this."
Smith theorizes that her findings make sense from an evolutionary perspective. "This is a time when a child is becoming an adult," she says. "In earlier societies and in animals, it's a time to leave the nest. So it's a time when an individual at puberty needs to begin figuring out life on their own. So to have an increased response to a complicated stressful event might be a learning experience, and it might be a phase we might all need to go through."
Fortunately for Sheryl Smith and other parents, puberty only last a few years. And Smith's daughter, Ashley, agrees that she can be moody -- like that time when they were shopping. "I guess I'm looking back on that now and saying 'It's not that big of a deal,'" she says.