Background: In a previous preliminary report, the perception of a decrease in ambient light intensity appeared to be correlated with depression. We prospectively studied this potential link in a controlled study.
Methods: The question, "I've noticed that the lights in my surroundings seem dimmer than usual", was added to the Center for Epidemiologic Studies Depression Scale (CES-D) questionnaire and administered prospectively to 213 subjects 50-80 years of age participating in the Age-Related Eye Disease Study (AREDS). All had visual acuity of 20/32 or better in at least one eye. Main outcome measures were the relationship between the dimness question answer and severity of depression, and the likelihood that patients reporting dimness were depressed.
Results: Subjects endorsing their surroundings as being dimmer than usual at least some of the time had a mean CES-D score of 10.6 (SD=7.0) compared to a mean of 5.5 (SD=5.4) for subjects who never noted dimness (t=-4.22, p=.0001). Depressed individuals (CES-D > or = 16) were significantly more likely to report dimness than non-depressed (CES-D<16) subjects (chi(2)=15.6, p<0.0001). The total CES-D score and the degree of reported dimness (0-3) were significantly associated (r=0.31, p<.0001). Using a stepwise regression analysis, subjects who reported any dimness were more likely to be depressed.
Limitations: A relatively small number of subjects, 38 (18%), reported dimness requiring us to dichotomize their dimness level in some analyses.
Conclusions: Perceived dimness of one's ambient surroundings and clinical depression are linked. Health care professionals should inquire about this symptom in potentially depressed patients.