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There are different types of positive emotions: You can be happy, enthusiastic, content, confident, interested, alert or blissful, among a number of other adjectives you might use when you feel more like smiling than frowning. All of these good feelings can be lumped together under the term positive affect, meaning the extent to which you experience yay-worthy emotions.

In general, positive affect has been linked to good sleep, but that doesn't mean that all positive emotions influence rest in the same way, or to the same degree. In a new study, researchers at the University of California, Irvine and Carnegie Mellon fleshed out the feel-good, sleep-well link. They found that "high-arousing" forms of positive affect, such as pep, vigor and enthusiasm, help with sleep more than low-arousing forms, such as calmness. 

Affect, in general, is the experience of having an emotion. Someone who scores high on positive affect enjoys good feelings frequently and intensely. Sometimes, researchers distinguish between state positive affect, a measure of how good you feel right now, and trait positive affect, a measure of your longer-term, overall proclivity towards positive emotions. So, an ordinarily peppy person who's having a crap sandwich of a day would score low on state positive affect, but high for trait.

Research on affect, both positive and negative, tends to be heavy on psych jargon. And, while some studies have simple, soundbite-friendly takeaways — "Messiness is a sign of intelligence" or "Cursing is good for you" — this is not one of those studies. Here are the main questions researchers set out to answer:

  • Is being in a good mood always beneficial to sleep, or does it do more for rest in certain contexts? Researchers hypothesized that positive affect has the biggest impact on sleep during periods of high stress, when positive emotions act as a buffer against the rest-ruining effects of stress. 
  • Do low-arousing and high-arousing types of positive affect influence sleep differently? It might seem like calm people have the advantage here since arousal typically isn't conducive to falling asleep. You're too stimulated to simmer down. But, stress also may be a more manageable monster if you have the high-energy disposition to handle it.

The study actually involved two separate studies. In both cases, participants were college students who assessed their moods (affect) and sleep habits. For the first study, 99 participants reported on two nights of sleep during the middle of the semester. The second study required (different) students to keep sleep diaries during final exams — presumably, a high-stress time on college campuses. Together, the two studies let researchers see how positive emotions affected students' sleep at varying stress levels. 

So, which students got the best sleep during finals? Pep-filled ones. 

Positive affect was linked to better sleep in both studies. But once researchers analyzed different types of positive affect separately, they saw that high-arousing feelings had a different relationship with sleep than calmness, or even happiness, which falls into the "mid-arousing" category, apparently. If this seems too abstract, think of the uber-chipper Chris Traeger on "Parks and Recreation" (Rob Lowe's character). That's the sort of person who could sleep like a log during finals, lit-rally.

Fleeting bouts of pep, however, did not appear to help students sleep during final exams. "The transient arousal paired with feelings of enthusiasm, vigor and so forth may not aid sleep in a given day," researchers wrote. 

Trait calm (being an overall calm person) also did not emerge as helpful for resting under stress. It wasn't clear whether or not state calm (feeling calm today, but not all the time) is useful for sleeping — the two studies didn't jibe in this respect. But, the confusing picture of calmness might have something to do with cultural ideals: Eastern cultures put calmness on a pedestal, but Americans are more likely to covet energy or enthusiasm. So, participants may not have evaluated calmness as researchers intended.

It's worth mentioning that researchers measured good sleep primarily in terms of sleep efficiency, which is the percentage of time in bed actually spent sleeping. They also considered sleep quality, which is a subjective assessment of restfulness upon waking up, and sleep duration, which is self-explanatory. 

It's a complicated study that leaves plenty of questions unanswered, such as whether or not positive affect has the same impact on sleep for night owls and morning birds.

And if you're still looking for a tidy takeaway, how about: Mad chill people don't always come out ahead.