It seems like the worst sort of cycle. The less sleep you get, the less effective you are. Then you have more to do, get more stressed, and stay up trying to get it all done (or lie awake stressing about it). The next day, less sleep, and even more anxiety.

The ironic part is that you might not be quite so anxious...if you could just get some SLEEP.

Goldstein et al. "Tired and Apprehensive: Anxiety Amplifies the Impact of Sleep Loss on Aversive Brain Anticipation" Journal of Neuroscience, 2013.

(I feel you, dude. Source)

The authors of this study wanted to look at anxiety responses in people, and how they were affected by lack of sleep. To do this, you need 19 healthy participants, an fMRI machine, a test of anxiety...and way to keep people up all night.

How do you assess anxiety responses? Start with cues, and then give outcomes.

You can see the layout of the studies above. The participants were placed in an fMRI scanner. During the recording, they were shown signs, followed by stimuli. If they got a negative sign, they would always get a negative stimuli (a man with a gun, which is plenty good enough to provoke an anxiety response). If they got a zero sign, they got a normal stimuli (a doorknob. Nothing scary there). If they got a question mark, they have a 50% chance of getting the negative stimulus. This question mark gives you an ambiguous stimulus, you don't know what to expect.

They had the participants go through the series of stimuli in two conditions: rested and sleep deprived. And when they sleep deprived them, BOY did they. Many sleep deprivation studies will restrict sleep to, say, 4 hours the night before the study, or 5. Not these guys. No, they had the participants pull an all-nighter!

And what did the sleep deprivation do? The authors looked at the amygdala and the anterior insula, brain regions important in memory and emotional processing, particularly in the processing of things like fear. fMRI measures blood oxygen levels in various areas of the brain. The idea is that increased blood flow (and thus oxygen flow) to a brain region means that the brain region is experiencing higher activity than others. Scientists usually examine this by comparing activity in the brain region to another region not in use (like, say, the cerebellum), or comparing it to a baseline reading where the participants are not getting any cues at all (as in this study).

In the rested participants, the signals in the amygdala and insula (showing "anticipatory" activity, anticipating what might show up next) were the strongest for the uncertain condition. But when people were sleep-deprived, they showed strong anticipatory responses for ALL the cues, neutral, negative, or uncertain. This means that being sleep deprived produces a higher response to negative cues. Less sleep is only going to make you MORE anxious.

But what about if you are anxious to begin with? The authors did a correlation, looking at the sleep-deprived responses, and correlating them with how the participants scored in baseline trait anxiety (how anxious they were generally, at baseline).

Above you can see the correlation between trait anxiety and the responses in the insula. You can see that the higher the trait anxiety, the higher the amygdala response following sleep loss. The correlation could mean that the higher anxiety you are, the worse you will get after sleep deprivation.

It's an interesting finding, and suggests that, if you're going to be facing negative things in the morning, the best way to prepare is to get a good night's sleep (though, of course, anticipating the negative things might ruin your sleep anyway). But of course, I think there are a few other things they could have done. While they did look at higher trait anxiety, showing a correlation between higher trait anxiety and a worse anxiety response to sleep deprivation, none of the participants actually HAD an anxiety disorder (that was explicitly excluded). I think it would be interesting to look at people with anxiety disorders as compared to people without, and see how they respond. If they have a really rough time, it could be something to think about for anxiety treatments.

I was also surprised to see that they didn't ASK the participants how nervous they felt after sleep deprivation (or if they did, they didn't show it) EDITED TO ADD: They DID in fact ask the participants about state anxiety, and it correlated with the responses in the amygdala and anterior insula. So good going there!. Showing activity in the amygdala is nice, but it would have been powerful to correlate it with how anxious overall people were feeling. There are also other tasks that they could have done to assess anxiety in the participants, and it would have been a nice backup if they did badly on those tasks as well. Finally, they could have looked at the stress hormone cortisol. Sleep deprivation is probably going to increase cortisol, but will it do so more, or less, in people with high trait anxiety? And does it correlate with the responses the authors saw in the amygdala? It would be interesting to see.

But in the meantime, I'm off to sleep. After all, I know the anxiety and stress will only get worse if I don't.

Goldstein et al. "Tired and Apprehensive: Anxiety Amplifies the Impact of Sleep Loss on Aversive Brain Anticipation" Journal of Neuroscience, 2013. DOI

UPDATE: Following some good points in the comments, I have updated the post to separate out the amgdala and anterior insula responses, as well as to note that they DID measure state anxiety, which I missed in my own sleep deprived state as I was writing. Thanks Neurocritic!