Every new mother has had a "mommy brain" moment. Maybe she finds herself incapable of following the assembly instructions on the new baby swing, or calling her best friend by the wrong name. During the exhausting and confusing first months of motherhood, brain freeze can become a familiar feeling.
Sheri Segal Glick of Mommyish blogged last year that choosing to stay home with her young children had lowered her IQ:
"Friends tell me that it all comes back to you when you go back to work, but I do worry that all of the grown-up, work-related knowledge that I once had is irretrievably lost. I worry that I will go back to work and will have to confess to clients that while I am unable to help them with any legal issue they might have, I can tell them what the very hungry caterpillar ate each day before he metamorphosed into a beautiful butterfly."
Though Segal Glick's piece has tongue firmly planted in cheek, she raises an interesting question: Could the rigours of motherhood make women "dumber" for good?
Though many women feel brain-deficient in the post-partum period, there's not a lot of research evidence out there to explain why, says Robyn Stremler, assistant professor at the Lawrence S. Bloomberg Faculty of Nursing at the University of Toronto.
"But lack of sleep is probably the easiest link to make," says Stremler. "We know from other populations, if you miss out on sleep, your brain does not function as well."
Stremler points out that missing out on just a little bit of sleep over a long period of time has also shown to cause cognitive difficulties, particularly with complex "executive" brain functions (like multi-tasking, planning, taking in a lot of different pieces of information and organizing them).
"It's that fragmentation of sleep -- you may be accumulating a decent number of hours across the night, but you're getting interrupted, so it means you're probably not getting the deeper, more restorative stages of sleep," says Stremler.
Lesley Fellows, associate professor of neurology and neurosurgery at McGill University, points out that it's not just frequent wake-ups that tax your brain. Because new moms are required to quickly learn a wide array of new skills and tasks in order to take care of their babies, their executive functions are suddenly working overtime.
"The need for those higher-level, executive processes goes up anytime you're faced with a new situation," she says. "So you're dumped into a new environment with a newborn, which puts more demands on your brain, and then it's weakened by not getting very much sleep, not to mention the emotional effects of the whole business."
SEE: How to get the best sleep. Story continues below:
Fortunately, as the duties of motherhood become more routine and sleep gets more regular, the demands on your brain are lessened, which should mean you can start thinking more clearly, says Fellows.
However, hormones can also have a negative effect on your brain function, says Jens Pruessner, director at the McGill Centre for Studies in Aging. Pregnant and post-partum moms have an excess of "steroid hormones" like cortisol, which is necessary for fetal development and to give them the energy to endure the strains of giving birth. However, these hormones can also have a negative effect on cognitive ability, says Pruessner.
"Cortisol is our major stress hormone, so it provides you with energy to cope with any increase in demand or any threat at hand, which is a good thing," he says. "But at the same time, it shuts down the areas in your brain that would allow you to think more clearly."
Disrupted sleep patterns can cause a rise in cortisol levels, says Pruessner.
"Every time you wake up in the middle of the night, you get a new kick in your cortisol system," he says, "Typically it's a good thing because it gives you the energy to get up and get going in the morning, but of course in the middle of the night, it's counter-productive." (That might explain why it can be so hard to get some shuteye after soothing the baby back to sleep.)
For some women, disrupted sleep can become a chronic problem, even once children start to sleep better. And if you are one of those people who is up and down throughout the night, elevated cortisol levels could have some long-term, permanent implications.
"Let's say you keep getting up at night for a period of a year or so, and you get that increase in cortisol," he says. "It's been shown that chronic and prolonged states of elevated cortisol can also lead to, or facilitate, neuro-degerenation. So this might lead to an acceleration in brain aging."
So interrupted sleep could lead to mothers' brain deteriorating?
"We all have neuro-degeneration, but it occurs at a very slow pace and normally it isn't anything to worry about because your body gives out long before your brain," says Pruessner. "But if you get into a situation where you now have these chronic elevations of cortisol, that might lead to additional wear and tear on your brain, and it has been associated with the onset of dementia, for example."
To stave off the potentially damaging effects of too much cortisol, make sleep a priority, says Pruessner.
"Try and get back to a normal sleep-wake pattern with a sufficient amount of sleep that would allow your system to recover from the stresses that occur during the day," says Pruessner. Robyn Stremler agrees.
"We used to think of nutrition and exercise as the key components to health, and I think more and more we're recognizing sleep is the other third piece, it's really necessary," she says.
As well, being a worrywort can also do you harm, says Pruessner. Anticipating negative outcomes (like constantly worrying about your child's well-being) can cause the release of cortisol as powerfully as if you experienced the negative effects themselves.
As Pruessner puts it, "Don't worry too much."