In the last few weeks, two studies were released that closely examine the causes and effects of unhealthy sleep habits. Lack of sleep could lead to a variety of physical and mental health problems. One of these studies confirmed a long-held truism: lack of sleep leads to anger and irritability.

According to the American Sleep Association (ASA), the average adult needs seven to eight hours of sleep a night. But 35.3% of American adults sleep less than 7 hours every night. The ASA found that 50-70 million American adults have a sleep disorder and 37.9% of American adults report falling asleep at least once during the day. While sleep is very important, it seems as if most Americans aren’t getting enough of it.

There are a few habits that people have that could be affecting sleep patterns. One of these bad habits is looking at smartphones before going to sleep. A new study from the Salk Institute found that when light-sensitive cells in the human eye are exposed to artificial light, like a smartphone screen, at night, it confuses the internal clock. If the internal clock is off, it could lead to poor sleep quality and other health issues connected with sleep, like cognitive dysfunction, cancer, obesity, insulin resistance, metabolic syndrome, migraines, insomnia and more.

Smartphone use late at night could lead to poor sleep quality and other health issues. Smartphone use late at night could lead to poor sleep quality and other health issues.

"Compared to other light-sensing cells in the eye, melanopsin cells respond as long as the light lasts, or even a few seconds longer," said Ludovic Mure, staff scientist and first author of the paper. "That's critical because our circadian clocks are designed to respond only to prolonged illumination."

"Our study suggests the two arrestins accomplish regeneration of melanopsin in a peculiar way," Professor Satchin Panda, senior author of the study said. "One arrestin does its conventional job of arresting the response, and the other helps the melanopsin protein reload its retinal light-sensing co-factor. When these two steps are done in quick succession, the cell appears to respond continuously to light."

The retina of the eye has an innermost layer that contains a subpopulation of light-sensitive cells. When these cells are exposed to ongoing light the cells continuously regenerate melanopsin. Melanopsin signals the levels of ambient light in the brain to regulate a person’s consciousness, sleep and alertness. It also is responsible for synchronizing the internal clock. After ten minutes of continuous light exposure, melanopsin signals the internal clock to reset. Bright light, such as from a smartphone screen, suppresses the melatonin in our bodies that helps with sleep regulation. Looking at a smartphone for a prolonged period at night signals to the body that it is daytime, throwing off everything that is preparing the person for sleep. This study was published in the journal Cell Reports.

So, looking at a phone leads to lack of sleep. How does lack of sleep effect mental wellbeing when a person is awake? A new study from Iowa State University has found that lack of sleep is linked to feeling more anger throughout the day. The study found that losing even an hour or two of sleep could make someone more likely to resort to anger during the following day.

The study broke participants down into two groups. Group one followed a normal sleep schedule, getting about seven hours of sleep. Group two restricted their sleep by two to four hours for two nights, averaging about four and a half hours of sleep per night. After the restricted sleep, all participants were asked to rate products while listening to brown noise or white noise. White noise created annoying conditions that may provoke anger. They rated the products before and after the sleep manipulation. The results of the study showed that sleep loss impacts anger. People who slept less were more likely to react in anger when reviewing products and listening to brown or white noise. This study was published in the Journal of Experimental Psychology: General.

There are devices being developed to help curb sleep issues that are linked to technology use, like tinted glasses that attempt to curb the negative effects of looking at screens at night. But the ASA says that practicing good sleep hygiene is the best way to guarantee a great night’s sleep. The ASA’s tips include going to sleep at the same time every night, sleep at least seven hours, use beds only for sleeping (no binging your favorite Netflix show in bed!) and practice quiet time before sleep are just a few of the sleep hygiene rules the ASA says people should follow.

Clearly, sleep is important to physical and mental wellbeing. It is imperative that people practice good sleep hygiene, even if that means putting technology down before going to sleep.