The number of patients who suffer from sleep disorders has nearly doubled in the last four years, and doctors are blaming the protracted recession.

According to a report by the Health Insurance Review and Assessment Service on Thursday, the number of patients who complain of insomnia has increased by a whopping 16.7 percent each year on average, from 207,000 in 2007 to 383,000 in 2011. As of last year, males accounted for 37 percent of patients and females for 63 percent.

People in their 50s were most at risk, accounting for 65.6 percent of patients.

"People tend to work longer hours amid the recession, and this has caused stress levels to increase. That may be the main cause of the rising number of insomnia patients," said Han Jin-kyu, head of the Seoul Sleep Center.

"Many people also stare at a computer monitor all day and then play with their mobiles in their breaks, so they become fatigued but can't sleep because of this continuous stimulation from all the electric light."

Shin Cheol, a professor at the Sleep Disorder Center of Korea University's Ansan Hospital, said, "Stress is the main factor causing insomnia among more than 90 percent of patients, so it's little wonder that the economic slump would have an impact."

As for the reason why there are almost twice as many female patients, the HIRA said, "Women in Korea often have a lot of stress, from child-caring to homemaking and work, and as they get older, and undergo more significant physical and emotional changes than men, they have to deal with much more stress."