The Deepest Well: Healing the Long-Term Effects of Childhood Trauma and Adversity—A Transformative Guide to Understanding Childhood Trauma and Health

by Nadine Burke Harris

The “lick your pups” study is a great example of this type of epigenetic regulation. Meaney and his team found that high-licker moms were releasing high levels of serotonin in their offspring. You may have heard that serotonin is the body’s natural antidepressant. It boosts mood and acts as the equivalent of rat-pup Prozac. This serotonin didn’t just make the pups feel better, it also activated a chemical process that changed the transcription of the part of the DNA that regulates the stress response. Meaney and colleagues eventually demonstrated that all that licking and grooming ultimately changed the epigenetic markers on the rat pups’ DNA, leading to lifelong changes in the stress response. This kind of epigenetic change is like a communication shortcut for nature. When rat moms don’t lick their pups, they are essentially telling them that there is something to be wary about in the environment, so they should be on high alert. Instead of waiting around for the generations-long process of genetic adaptation to change the offspring’s DNA, this environmental information gets passed on to the rat pup quickly through a change in the epigenome. To look more closely at this process, the Meaney research team did something brilliant; taking a cue from a Lifetime TV movie, they switched some of the rat pups at birth. They placed pups of high-licker moms with moms who were low lickers, and vice versa. The study found that the pups’ DNA methylation took on the pattern of their fos...