Format

Send to

Choose Destination
See comment in PubMed Commons below
Chronobiol Int. 1998 Nov;15(6):623-32.

Absence of seasonal variation in the phase of the endogenous circadian rhythm in humans.

Author information

1
Unit for Experimental Psychiatry, University of Pennsylvania. VDongen@Mail.Med.UPenn.edu

Abstract

Humans may be subject to seasonal variations, as evidenced by the existence of seasonal affective disorder (SAD) and midwinter insomnia. However, some recent studies have shown that the seasonal variation in the phase of the circadian rhythm is relatively weak in healthy humans. In the present study, evidence is found that there is no seasonal variation in the phase of the endogenous circadian rhythm at all. Body temperature, cortisol excretion, and subjective alertness of six subjects recorded under constant routine conditions showed no systematic seasonal variation in circadian phases. This finding indicates that secondary zeitgebers blocked or counterbalanced the seasonal variation in the entrainment effect of the natural photoperiod. The human being may live in an environment in which the photoperiod has lost its status of primary zeitgeber.

PMID:
9844750
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Loading ...
    Support Center