A Study on the Changes of the Biological Rhythm by Display Image Modulation

Effects of Smartphone Use at Night with Light Emitting Diode Display With and Without Blue Light in Healthy Adults: A Randomized, Double-blind, Cross-over, Placebo-controlled Comparison

Inclusion Criteria:

(1) Healthy males 20-40 years of age who understood the study procedure and agreed to participate after being fully informed about the study were included.

Exclusion Criteria:

1. psychiatric diseases according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria;15
2. cognitive or neurological disorders;
3. alcohol or substance abuse;
4. unstable or serious medical illness;
5. current use of psychoactive mediations including antidepressants, anxiolytics, neuroleptics, anticonvulsants, hypnotics, or stimulant medications;
6. primary sleep disorder;
7. habitual sleep onset earlier than 21:00 or later than 24:00;
8. shift worker;
9. travel across more than two time zones within 90 days of the study; and
10. ophthalmologic disease during the study period.