Not only does getting enough sleep make you happy, but being a happy person could help you achieve a good night's sleep, according to a small study from Cornell University researchers.
The study, published in the journal Annals of Behavioral Medicine, shows an association between sustained positive life outlook and increased quality of sleep.
However, researchers also found that people who had more "unstable" positive emotions -- meaning their positive feelings were highly "reactive" and tied to external events -- also had a higher likelihood of experiencing poor sleep.
"[While] possessing relatively stable high levels of positive emotion may be conducive to improved sleep, unstable highly positive feelings may be associated with poor sleep because such emotions are subject to the vicissitudes of daily influences," study researcher Anthony Ong, an associate professor of human development at the university, said in a statement.
Ong and colleagues from Arizona State University, Penn State University and the University of London conducted their study on 100 people in the U.S. who are all in middle age. They conducted phone interviews to gauge their daily emotions, and also took objective and subjective measurements of the participants' sleep.