Wednesday, May 27, 2009

Cortisol: Friend or Foe?

The much studied and much misunderstood hormone cortisol is generally an unwelcome visitor to a baby's developing brain. But research has show that as the child grows up, the brain actually requires small amounts of cortisol to mature. This is the final post in a series of three that I have written about an infant's brain development after reading Sue Gerhardt's excellent book "Why Love Matters".

Babies and toddlers rely on adults to regulate their emotional state. That is one of the reasons why it is so important for a child to have a constantly present attachment figure, though this does not necessarily have to be a parent. The child's very survival depends upon the attachment figure and consequently the child is extremely sensitive to the positive and negative messages given by the adult.

A parent's positive face tiggers off a pleasurable reaction in a baby. The baby's heart rate increases, and beta-endorphin and dopamine are released. Beta-endorphin is an opioid and dopamine is a stimulant so both make the baby feel good. Both also help the young baby's brain to grow by increasing the brain's uptake of glucose. This is why positive interaction with a young baby is so vitally important.

But the flip side of the baby's pleasurable reaction to a happy face is its negative reaction to an angry or sad face. Seeing a negative expression on its parent's face is itself a stressful event for a baby, triggering the baby's stress response. The stress response is sometimes described as the HPA axis, which is shorthand for "hypothalamus triggers pituitary gland which triggers adrenal glands". Each of these glands produce hormones, the most famous of which is cortisol, produced by the adrenal glands. Although there are several hormones involved in the stress response, it is cortisol that is the most widely studied because it can be measured in saliva.

It is accepted that during babyhood, cortisol is detrimental to the development of a baby's brain. Since babies are unable to self-regulate their stress levels, they require their adult caregivers to repeatedly return them to a state of equilibrium by meeting their needs for food, comfort, safety and love. But in toddlerhood, something interesting happens to the role of cortisol in the child's brain. A toddler actually needs some cortisol to complete the development of their orbitofrontal cortex - the part of the brain that controls how the child responds to basic emotions such as fear and anger. Gerhardt explains:
"Increased levels of cortisol facilitate the growth of norepinephrine connections from the medulla up to the prefrontal cortex. This delivery of norepinephrine helps the orbitofrontal cortex to mature further in toddlerhood, by increasing blood flow to the area and by forming its links (via the hypothalamus) with the parasympathetic nervous system. The parasympathetic nervous system is vital to the growing child, because this is the inhibitory system which enables the child to stop doing something and to learn what behaviour is unacceptable or dangerous."
The requirement for some brief does of cortisol coincides very neatly with the period in a child's life when it is becoming mobile and inquisitive, and often putting itself in danger. When the parents scold the child or simply stop it from doing something, their negative facial expressions set off the child's stress response, giving his body a quick shot of cortisol. However, too much cortisol would still be bad for the developing brain and so it is important that the parents once again restore the child to its emotional equilibrium state quickly.

Parents of toddlers apparently say "No" an average of once every nine minutes - but at least they can do it in the knowledge that they are performing an essential role in their child's development!

"Why Love Matters" is divided into three sections on brain development, the consequences of a dysfunctional childhood, and the way forward. The three posts I have written have all been based on material from the first section on normal infant brain development. But the whole book is a fascinating read and I would wholeheartedly recommend it. And if you have any book recommendations of your own, please tell me in the comments - I would love to read more well thought out, well researched books on parenting.

If you enjoyed this post, you may like to read the earlier posts on the book: Why Are Human Infants Born So Prematurely and Why It Is Wrong To Leave A Young Baby To Cry.


allgrownup said...

You will have read it I'm sure: The Attachment Parenting Book, Sears. Also, I'm expecting at the moment, and this is a fab pregnancy read: Blooming Birth, Lucy Atkins & Julia Guderian. Gave me confidence to give birth my way, and this time, lessening my c-section fears.

willow81 said...

Thanks for your summary of Why Love Matters, I've had it sitting on my shelf for ages and have never managed to finish it. I can see that we are approaching the time when those doses of cortisol are beginning to make an appearance. It is amazing how quickly it all happens, a calm "no" or taking her away from something dangerous and it's suddenly MAJOR TANTRUM. She is discovering her will and it is terrifying!

Liz said...

Have you read Toxic Childhood by Sue Palmer and Hold On To Your Kids by Dr Gordon Neufeld? I found both of them very interesting.

Katherine said...

A really thought provoking post. Sue Palmer is a fab read too. I like a lot of her articles and Toxic Childhood is especially good. Will try and track down Why Love Matters. I find these studies fascinating from both a parent and teachers point of view.

Mon said...

Thanks for sharing this book with us.

Man, it makes me sad to read that a caregiver's happy face triggers pleasurable reactions, only because I'm thinking of babies in orphanages etc, you know?

It does make me feel like all that effort to be calm and happy and smiling for her was worth something.

Anyway, the theory that there's a need for some cortisol during toddlerhood might help some parents accept those crazy years a little more, lol

allgrownup said...

Just borrowed why love matters from the stock of books at my breastfeeding group :-)

Cave Mother said...

allgrownup: Actually I haven't read any books on attachment parenting, quite deliberately really. I'm not that into books that tell me how to do things and I want to avoid following any one author's rules. But I did have a read of that birth book in WH Smith when I was pregnant (along with just about every other book on birth!), and I liked the way it talked about natural birth. My fave pregnancy and birth book was by Sheila Kitzinger. I really like the no-nonsense, positive approach she has. Maybe one day I will read the Sears books - when it's too late to worry about what I'm doing wrong!

Liz and Katherine - thanks for those recommendations. I will get hold of them.

Cave Mother said...

Oh, and Mon: one of the things mentioned in Why Love Matters was the brains of children raised in Romanian orphanages. Part of their orbitofrontal cortexes were found to be almost non-existent due to the lack of stimulation it had received. Pretty scary stuff.

Anonymous said...

Thanks for the great info. I just reserved Why Love Matters at my library. Sounds like a good read.

The Awakened Heart said...

Interesting post. My wee boy will be coming into this stage soon. Though I think I have enough cortisol for everyone in this family! Thanks for the book recommendation too.