We all have memories of important things that happened to us as children – good and bad experiences that we look back on as formative. What we're learning is that these early influences can be even more profound than we used to think. Childhood experiences affect the course of our entire lives, from our health to our success to our happiness, and even to how long we'll live.
On Thursday, we will be participating in a symposium put on by the Canadian Institute for Advanced Research (CIFAR) in honour of the late Clyde Hertzman. A professor at UBC and an expert in early learning, Clyde was a long-time CIFAR senior fellow who strongly affected the way we understand the influence childhood plays on our lives. He coined the term "biological embedding" to describe how early childhood influences could literally get under our skin, creating physical and emotional changes for good and bad.
Neglect and abuse, disadvantages and stress early on can lead to overall poorer health, difficulty learning, and poor social functioning that can result in a lifetime of problems. Research from a number of fields, including molecular genetics, evolutionary biology, neuroscience, social and behavioral sciences and epidemiology, is allowing us to understand how and why this occurs, and could help us make life-altering interventions.
Sir Michael Marmot, who conducted the Whitehall study on British civil servants during the 1980s, was one of the first to draw attention to social determinants of health. He showed that within the civil service, minor gradations in status and pay were associated with poorer health outcomes. Dr. Hertzman was strongly influenced by the work, and became especially concerned with these sorts of effects on children.
We've made great progress in teasing out some of the biological causes and effects. Work by Bruce McEwen of Rockefeller University, among others, has shown how pre- and post-natal stress affects the neuroendocrine system, which controls our reactions to stress, as well as functions such as digestion, the immune system and the storage and expenditure of energy. A stressful early environment can lead to stress responses going on permanent overdrive, resulting in suppressed immune systems and impairment of parts of the brain that affect learning and memory.
One important area of research is looking at the interaction of genes with the environment. We're interested in work that suggests different versions of some genes can make people more or less reactive in their stress responses. Some genetic makeups seem to protect against early adversity, while others make people more prone to damage.
Early environments can also have an epigenetic effect, determining which of our genes are turned on and off. Baby rats that are licked and groomed a lot are better able to deal with stress later in life. Work by Michael Meany of McGill showed that when pups are not licked and groomed enough, a gene involved in the stress axis that codes for glucocorticoid receptors – which mop up the stress hormone cortisol – is modified, so that the pup ends up with fewer of those receptors in its brain, and is less able to deal with the damaging effects of stress later on.
One of us, Marla Sokolowski, looked at how genes and environments can interact in fruit flies. Exploratory behavior in flies is important for finding food and mates, and flies that exhibit less of the behavior are less fit. Depriving fruit flies in the larval stage of nutrition led those flies with one gene variant to engage in more exploratory behavior, and to show more reproductive success. Flies with another variant were unaffected. What this tells us is that organisms will have a tougher time dealing with early adversity, depending on their genetic makeup.
We think the same thing happens with children. Some seem to be "dandelions," who can overcome early adversity. Others are "orchids," who thrive in a nurturing environment but do poorly in a stressful one. Teasing out the genetic differences, and possibly identifying them early, could have a huge effect on children's lives.
We can also see many effects on people through epidemiological studies. For instance results by one of us, Tom Boyce, show that poverty experienced in very early childhood, between the prenatal period and the second year of life, is associated with early-adult hypertension, arthritis, and limitations on daily living, effects that seem to be caused by changes to the immune system.
There are still questions to be answered, about how genes and the environment link up to social contexts and the brain; about which social conditions affect the growing brain; about how different genetic variants influence the brain; and many more.
But we already know enough to say that children who are at risk can benefit from nutritional, financial, educational and emotional interventions. How that can best be done will be one of the topics of the symposium later this week. What we know is that we can help children who, through no fault of their own, are at risk of failing to live up to their potential.
W. Thomas Boyce (UCSF) is a senior fellow and co-director of CIFAR's program in Child and Brain Development. Marla B. Sokolowski (University of Toronto) is the CIFAR Weston fellow and co-director of CIFAR's program in Child and Brain Development. The CIFAR symposium From Cell to Society: Creating a world where all children can succeed takes place on February 6, 2014, and will be broadcast online at cifar.ca/webcast.