Nightmares and insomnia contribute independently and additively to depression severity, cross-sectional study findings show.
The researchers, led by Yuichi Inoue (Tokyo Medical University, Shinjuku-Ku, Japan), say the finding highlights “the necessity of assessment of these two symptoms to prevent the aggravation of depression.”
Among 2822 individuals, with an average age of 57 years, who completed the Pittsburgh Sleep Quality Index (PSQI) and the Center for Epidemiological Studies Depression (CES-D) scale, 25.5% had insomnia and 4.6% experienced nightmares at least once a week.
Multiple regression analysis showed that scores for both insomnia and nightmares were significantly associated with an increase in depression scores, age being the only other independent factor.
There was evidence of an additive effect among patients with both conditions. Average CES-D scores in 83 patients with coexisting insomnia and nightmares, 527 individuals with insomnia alone and 42 with nightmares alone were approximately 13, 11 and 10, respectively, compared with 8 for 1791 control individuals.
The higher score among individuals with both conditions was significantly so compared with all of the other groups. The difference was also significant between individuals with insomnia alone and controls, but not between individuals with insomnia alone and nightmares alone.
“Results showed that nightmares and insomnia symptoms mutually aggravate depressive symptoms when these two symptoms coexist,” the researchers write.
But they note in Sleep Medicine that total CES-D score in participants experiencing nightmares three or more times a week was similar to the score in those experiencing nightmares only once or twice a week.
This “might indicate that the presence rather than the frequency of nightmares influences depression”, they point out.
This article first appeared on News Medical on 24 March, 2014.