**Dear GQ Doc,
Why is it that when I wake up really tired I sometimes feel sick?
Ted, via email.**
I have absolutely no idea. I mean, usually there’s at least some vague notion percolating in my head (and hopefully enough to formulate a theory), but this time I am officially cognitively dry. So I went to the research papers. Nothing concrete there. The forums? Don’t ask. Going offline, I regressed to the medical textbooks. Again, nothing solid. To answer this, it was time to go back to basics and reverse engineer the question...
What is nausea?
Start simple. This is that unpleasant and painless subjective feeling that you are about to vomit. It doesn’t always mean that you will but you might.
How does the body make you feel nauseous?
Less simple. Ultimately it is an unbelievably complex physiological process (that nobody really fully understands) triggered by interactions between your psychological states, nervous systems, dysregulation in your gastrointestinal system (especially your stomach) and your endocrine (hormone) system. In short, your stomach and your brain talk shit to each other. Which is in part why your stomach is called your "second brain".
Why call your stomach your second brain?
Between your stomach and brain is a motorway of nerves, chemicals and hormones. Their role is to feed back how hungry you are and, interestingly, whether you are experiencing stress. And it’s not a one-way street. Not only can your stomach send messages to your brain about the state of your gut, this motorway also allows for your brain to directly impact your stomach – including triggering the production of excess acid when stressed.
Five reasons this nausea pathway is activated when exhausted
Here's the rub. There are more than 93 causes of nausea, a list with broad categories from drugs and alcohol, gastrointestinal and cardiac disorders, to cancer and central nervous system dysfunction. But we don't have time for all that. Instead, here are the five most suspected factors that may trigger the nausea process when waking early or exhausted.
1. Stress
Your stomach produces excess acid when stressed or tired and this in turn irritates its lining and triggers nausea. It then settles with food by dissipating your stomach acids.
2. Dehydration
A dehydrated body can trigger nausea. Overnight it’s easy to dehydrate (and exacerbated if you’ve had some alcohol). When you take on fluid, the symptoms settle.
3. Elevated vasopressin hormone
Made in the hypothalamus of your brain, vasopressin rises due to our first two factors (dehydration and stress) and is associated with nausea onset.
4. Central nervous system response to waking
The shock of waking when exhausted triggers a rapid spike in your sympathetic (fight or flight) nervous system and can trigger nausea.
5. Low blood sugars
Heavy meals can trigger a blood sugar crash (due to the insulin spike), which among other symptoms, causes nausea.
Basically, we’ve no idea and it’s probably a mix of all the above.
Irrespective, the treatment seems to be get over the shock, grab breakfast and have a nap later.
Dr Nick Knight is a GP. Follow him on Twitter @DrNickKnight.
