Getting stressed or anxious during late pregnancy is not just bad for you, it's bad for your foetus. There is now overwhelming evidence that Attention Deficit and Hyperactivity Disorder and behaviour problems are directly caused by maternal stress during pregnancy. There are big implications, not the least of which is that the repeated claim that ADHD should be regarded as having a largely genetic cause requiring a pill-based solution is no longer defensible.
The story starts with the relationship between the hypothalamus, the pituitary gland and adrenaline: the HPA axis. It prepares us for fight or flight when confronted by threat. By measuring cortisol levels we can identify how much the HPA axis has been activated.
If you are placed in stressful circumstances, your HPA may be jammed on. Mostly, this results in high levels of cortisol, which reduces your life expectancy, and makes you into a gibbering wreck. Your heart races, your palms sweat, your eyeballs start extending out on stalks. It takes only the smallest stimulus for you to overreact.
Alternatively, having the HPA jammed on means that your system closes down and cortisol levels are abnormally low. You are so used to feeling threatened that a three-headed Martian could appear and you would say "Hey, dude, how's it going?"
A large body of evidence now shows that your baseline cortisol level, the thermostatic position to which you return when a threat has passed, is set in early childhood. Having a depressed mother who does not respond to your needs or receiving unresponsive daycare as a baby or toddler, create a permanent insecurity that becomes electrochemically enshrined as abnormally high or low baseline cortisol levels.
However, the latest evidence shows that the thermostat is also set prenatally. Several groups of children have been followed from before birth to late childhood. At seven to 10, those whose mothers were stressed or anxious years before, in pregnancy, were significantly more likely to have ADHD symptoms, behavioural problems and anxiety.
The HPA axis and cortisol explain these findings. All these disorders correlate with abnormal cortisol levels. Prenatal stress activates the mother's HPA, jacking up cortisol levels, which are passed via the placenta to the foetus.
If the government really does give a damn about rising crime, disorder in the classroom etc, maternity leave needs to extend to the last trimester, prenatally. As regards hyperactive trouble-making children, the message is not to blame their genes and choose psychotherapy instead rather than joining the 340,000 children on Ritalin-like medication.
O'Connor, TG, 2005, Biological Psychiatry, 58, 211-17. More Oliver James at selfishcapitalist.com
