laboratory experiment · n=8
Human phase response curve to a single bright light pulse
Journal of Physiology · 1999
Open PubMed recordDOI 10.1111/j.1469-7793.1999.00891.xenvironment
Morning light timing is irrelevant
Grade B · ModerateHuman reviewed
What people say
“It does not matter when I get daylight; only bedtime matters.”
What the evidence says
Grade B · ModerateHuman circadian experiments show light can shift biological timing, with effects depending on when it is received. This supports light timing as one factor, not a stand-alone cure for insomnia.
Research record
What this verdict is based on
Sources are linked for inspection. Study results are summarized for general information, not personal medical direction.