A study on sleep pattern and time, conducted by researchers from University of Adelaide, has found that lack of sleep can make a person feel depressed and ill. According to the researchers, over 2,000 people from Australia were included in the study. Participants were aged between 35 and 83.

At the start of the study, the researchers adjusted risk factors like sex, age and race. After that, they observed the participants for about five years. The researchers said they have found that sleepiness during daytime increases the risk of depression by about 10%.

After analyzing about 90,000 people in 18 countries, the researchers found that people in the wealthier countries were more likely to experience depression than the people of poor or low-income nations. According to the researchers, the depression could be associated with income inequality. Money could the key reason why people feel sad, the researchers said.

According to some researchers, it is difficult to say whether sleep problems are linked to money. They said that sleep disorders could be more than just signs of being depressed.

After analyzing samples of Australian participants, the researchers found that there could be a link between having sleep disorder and depression. The Los Angeles Times reported that the study from the University of Adelaide researchers concluded that people with excessive daytime sleepiness could be 10% more likely to be depressed than people without it.

The study stated, "Those who have developed sleep apnea are 2.1 times more likely to be depressed too. Some people included in the survey both suffer from EDS and sleep apnea. They are 4.2 times more likely to be depressed".