One in five adults in Japan depends on alcohol and drugs to fall asleep, a national health survey carried out by the health ministry in 2007 showed Thursday.

By sex, the breakdown was 22.2 percent for males, up 2.3 points from 2003, and 17.4 percent for females, up 1.7 points, the survey said, without providing the total number polled.

With 57.9 percent of men and 63.9 percent of women describing themselves as under stress, the ministry reckoned their dependence on alcohol and drugs was being caused by their stressful lifestyles.

"We plan to promote further research in this area," a Health, Labor and Welfare Ministry official said.