I have a bullshit switch. It gets triggered when I hear certain phrases. ‘Neuroplasticity’ is one, ‘hemisphere’ is another and ‘raises dopamine’ is a regular button pusher. That’s not to say people can’t use these phrases while talking perfect sense, but I find it useful that they put me on my guard.
Most recently, I’ve found the phrase ‘raises cortisol’ to be a useful way of alerting me to the fact that the subsequent words may be a few data points short of a bar graph – potentially some poorly understood drivel.
This has been recently by demonstrated by scaremongering advice handed out to parents based on the claim that some vaguely specified study has ‘shown’ that something or other ‘raises cortisol levels’ in children.
The experts then go on to explain that cortisol is ‘bad’ for the developing brain because, as we all know, at least according to the scientific stereotype, cortisol is the ‘stress hormone’.
A few weeks ago psychologist Penelope Leach claimed that leaving babies to cry means “huge quantities of the stress hormone cortisol are being released in that baby’s brain, flooding his brain and his central nervous system, and one of the things we’ve learnt is that lots of cortisol washing about is really not good for the developing brain”.
This claim is apparently also in her new book and it made headlines around the world: ‘Crying babies at risk of brain damage’, ‘Leaving your baby to cry could damage its brain new book claims’, ‘Letting newborns cry is bad for them: study’ and so on.
The excellent Neuroskeptic blog noticed that ubiquitous psychologist Oliver James was recently advising people that leaving children in childcare could raise the risk of behaviour problems later in life because a study found that cortisol “levels had doubled within an hour of the mother leaving them in daycare”.
These claims both reflect one-dimensional thinking about how the brain works. Yes, stress tends to raise cortisol levels and there is good evidence to suggest that chronically high levels of stress and cortisol may be detrimental to brain, but this conclusion is typically drawn from people who have been through some fairly serious shit, wars, deprivation, trauma, or have specific hormone problems.
There is remarkably little research on cortisol, everyday stresses in young children and none to suggest normal variation damages the brain in any way. In fact, a couple of studies suggest that higher cortisol levels in young children are related to better mental performance but you probably won’t hear about these. You’ll also not hear about the recent study in the Journal of Pediatrics that found that breast-fed infants had higher cortisol levels.
That’s not to say that all of the studies have found a positive effect (there’s a fair research base on how higher cortisol levels during pregnancy can, in some situations, lead to later problems) but just that its common that ‘experts’ in vaguely related field will cherry pick brain studies to support what they already say.
This is particularly effective when it chimes with our folk neuroscience: dopamine equals addiction, cortisol equals stress, serotonin equals enjoyment, the right-hemisphere equals creativity and so on. None of which makes sense its own. They’re all useless when used as stereotypes.
As Neuroskeptic notes, virtually every form of physical activity raises cortisol levels, so you can’t just blithely apply the over-generalisation without making a nonsense of the world.
Or indeed, of childcare.
Link to Neuroskeptic on cortisol and pop childcare advice.