Extreme Stress-Related Drowsiness

Hello everyone.

Like most posters here, I've come for some advice and I'm hoping you could help.

I have a friend who has a problem with bouts of extreme drowsiness. Some years ago, he would have hot flashes and have to lie down, maybe eat or drink something, and then, about 10-20 minutes later, he'd feel better again. Over the years, this has gotten steadily worse, and now, rather than hot flashes solved by food and rest, he just...shuts down. He can be fine for a while, and then, out of nowhere, he'll start yawning and nodding off and nothing will help except going to bed until the feeling passes. Lately, the drowsiness is getting heavier and it's starting to last longer (over an hour sometimes). He describes it like being very, very drunk.

He's had his blood pressure, blood sugar, and heart and all checked out, has gone to all the doctors you can think of, both for modern and traditional medicines (including acupuncture, homeopathy, etc). No one has found a cause for this drowsiness. As far as any doctor can tell, he's healthy. No problems with his heart, his brain, no tumours, nothing. We've also tried to link this with food, such as caffeine (which he does drink a fair amount of) or alcohol (which he'll also drink, but never to any excess), with no success. Changes in diet don't help either.

The reason I'm posting this here is because I have a strong suspicious that this is stress-related. My friend has had heavy anxiety, depression, and PTSD for most of his life, and while he's done a pretty good job of outwardly coping with all of this, I think he's internalised a lot. At a guess, I would say that he's been so wrung-out by all the stress he's had in the past that he now has a very low tolerance and will get an extreme response to even the slightest stressor. If there is any one thing that correlates even a little with these sleepiness spells, it's stress. He'll get worse if he's stressed about something, even if that something is fairly minor, like bad traffic causing him to be late somewhere. He's tried all sorts of counselling and meditation and various workshops for dealing with stress, with limited success. Given that he internalises a lot of it, I think there's probably some level where he's not even consciously aware of the stress - his body just responds automatically.

This being said...he is also taking Lexapro to lessen stress, and has been for years. Could this drowsiness be a side-effect of the years of Lexapro use? If it is, he'd have to cut back on using it, but if not, then cutting back might only make the problem stronger.

Has anyone had any experience with anything like this before and could offer some advice on what to do next? We're getting worried because it's getting worse, and we don't know how much worse it might still get. We aren't even sure of the cause, nevermind the solution. He's tried just about everything anyone can think of and nothing has worked, so I'm hoping that maybe someone here will think of something new.

Thank you for reading and for any words of advice.