Loving Your Child

Brain Development & Stress

Our brain development begins shortly after conception and continues into our 20s.

As our brain develops..

our brain development begins shortly after conception and continues into our 20s. Babies are born with most of the neurons they will have throughout their lives, what forms in the early years is the connections between the neurons.

Most connections are formed within the first 3 years of life.  For each connection there is a critical or sensitive period, this is a time when the connection is most malleable. These critical or sensitive periods are a time frame in which most learning in a particular area occurs.

Photo by Public Domain Pictures on Pexels.com

Most critical periods are in the first 5 years of life. Our brains are built from the bottom up, meaning, complex brain circuits (executive functions) are built on top of more simple brain circuits. For example, the critical or sensitive period for neuron connections related to vision, hearing and touch tend to develop in the first few years of life. In contrast, the critical or sensitive period for neuron connections related to more complex areas of development such as communication, reasoning, and decision-making will occur later in development. Therefore, it is critical that children receive attention, instruction, and nurturing for age-appropriate areas of development that are occurring at east specific critical or sensitive period. If certain connections are not strengthened and are lost, this can impact future development of more complex connections. 1

Once connections are formed in the brain, our childhood experiences either strengthen these connections building strong foundation for future development, or they weaken these connections through a process called “pruning”. The more a child uses a connection (carry out a specific task or behaviour) the stronger the connection becomes. If a child does not have opportunities to use and strengthen connections, they can be lost, this is called “pruning”. Strong connections build a sturdy foundation which promote a healthy developing brain. Exposure to trauma, negative relationships, and neglect can lead to weaker brain foundations and higher rates of pruning. These weak brain foundations can lead to health and mental health challenges later in life. 1 The video by the Alberta Health & Wellness Initiative demonstrates the importance of early childhood experiences on healthy brain development. 1

Serve & Return 

Photo by Sharon McCutcheon on Pexels.com

Serve and return interactions between children and caregivers/adults help shape brain development. Research has shown that children learn best when an attentive adult is engaged with them throughout the learning process.  This video by the Alberta Health & Wellness Initiative (June 2014) illustrates how the “Serve & Return” process can positive impact healthy brain development. 1  

How Early Life Stress Shapes our Brain

There are three main types of stress: 2

During stressful situations our brain produces a hormone called “cortisol”. When the stressful situation has subsided and the perceived threat is gone, cortisol signals the brain to stop producing more cortisol. While cortisol has many positive functions within the body, high levels of cortisol can cause long-lasting damage to the brain.

“Allostasis” is a term used to describe the body’s ability to adapt to cortisol making it harder for the brain to shut down its response to stress over time. This can lead to “high allostatic load” which is the deterioration of the brain due to exposure to high levels of stress over time.1  Research has shown that positive caregiver attachment can act as a buffer to chronic stress response. For example, one study by Nachmias et al (1996) showed that children (age 18 months) exposed to a frightening stimulus who had a secure caregiver attachment showed lower levels of cortisol than same age children exposed to the same stimuli with insecure caregiver attachment. 3This video on “Toxic Stress” by the Alberta Family Wellness Initiative (June 2014) further describes the impact toxic stress in childhood can have on brain development. 1 For more information, see the resources below.


  • Center on the Developing Child Harvard University. (2019) Toxic Stress. Retrieved from:
  • Nachmias, M., Gunnar, M., Mangelsdorf, S., Parritz, R.H., & Buss, K. (1996). Behavioural Inhibition and Stress Reactivity: The Moderating Role of Attachment Security. Child Development 67(2), p. 508522.


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