Nighttime outdoor artificial light linked to mental disorders among adolescents

Area-level artificial light at night, or ALAN, may negatively affect sleep patterns and increase risk for mood and anxiety disorders among adolescents, according to results of a study published in JAMA Psychiatry.

“Several community-based and population-based studies have demonstrated associations between outdoor ALAN and sleep patterns,” Diana Paksarian, PhD, of NIMH’s Intramural Research Program, and colleagues wrote. “ALAN has also gained attention as a risk factor for chronic diseases, particularly cancer and obesity. To our knowledge, only one prior study has focused on the association between outdoor ALAN and mental health at the population level.”

This prior study, which was conducted among South Korean adults, showed that those who lived in districts with higher outdoor light levels were more likely to report suicidal ideation or attempt and depressive symptoms. Despite results of this study, little remains known regarding the link between nighttime outdoor light levels and sleep and mental health at a population level, especially among adolescents.

In the current population-based, cross-sectional study, the investigators sought to estimate associations between outdoor ALAN and sleep patterns, as well as past-year mental disorders among U.S. adolescents. They collected data of 10,123 adolescents who were included in the nationally representative cross-sectional National Comorbidity Survey-Adolescent Supplement from February 2001 through January 2004. Data included a probability sample of adolescents aged 13 to 18 years.

Satellite-measured outdoor ALAN levels served as the main exposure. Main outcomes and measures included self-reported habitual sleep patterns — weeknight bedtime, weeknight sleep duration, weekend bedtime delay and weekend oversleep — as well as past-year mood, anxiety, behavior and substance use disorders, which were measured using an in-person structured diagnostic interview. Behavior disorder diagnoses included parent-reported information.

Results showed a positive association between ALAN and social disadvantage indicators, including racial/ethnic minority status and lower family income. Adjustment for multiple several sociodemographic characteristics, as well as area-level population density and socioeconomic status, showed an association between higher ALAN levels and later weeknight bedtime. Those in the lowest ALAN quartile reported the longest weeknight sleep duration. Those in the highest ALAN quartile reported going to bed 29 minutes later and receiving 11 fewer minutes of sleep than those in the lowest quartile. Moreover, the researchers observed a positive association between ALAN and prevalence of past-year mood and anxiety disorder. Every median absolute deviation increase in ALAN was linked to 1.07 (95% CI, 1-1.14) times the odds of mood disorder and 1.1 (95% CI, 1.05-1.16) times the odds of anxiety disorder. They also reported associations with bipolar disorder (OR = 1.19; 95% CI, 1.05-1.35), specific phobias (OR = 1.18; 95% CI, 1.11-1.26) and major depressive disorder or dysthymia (OR = 1.07; 95% CI, 1-1.15). Adolescent girls’ differences in weeknight bedtime by ALAN were greater with increasing years since menarche.

“Further research is needed to evaluate the role of other contextual and individual-level risk factors in the association between ALAN and mental disorder,” Paksarian and colleagues wrote. “Future studies should elucidate whether public interventions designed to reduce the brightness or spectral composition of outdoor nighttime lighting could benefit mental and sleep health among youth, especially those who face other sources of social disadvantage. For example, studies investigating the effects of changes in street lighting could include health outcomes, such as sleep and mood, to weigh the benefits and perceived disadvantages of such interventions.”