Sleep and Circadian Rhythm Disruption in Social Jetlag and Mental Illness - Progress in Molecular Biology and Translational Science - page 326

SCRD can be particularly severe when social timing forces an abnormal pattern of sleep
and wake upon our endogenous sleep biology.
SCRD is also very common in mental illness, and although well known, this associ-
ation is poorly understood or treated. Recent studies suggest that the generation of
sleep and mental health shares overlapping neural mechanisms such that defects in
these endogenous pathways result in pathologies to both behaviors. The evidence
for this association is examined in some detail.
We conclude this review by suggesting that the emerging understanding of the
neurobiology of sleep/wake behavior, and of the health consequences of sleep disrup-
tion, will provide new ways to decrease the conflict between biological and societal
timing in both the healthy and individuals with mental illness.
1. THE BIOLOGY OF SLEEP
Sleep is a highly complex behavior arising from an interaction
between multiple neural circuits, neurotransmitters, and hormones, none
of which are exclusive to the generation of sleep. 1 The major brain structures
and neurotransmitter systems involved in the sleep/wake cycle are summa-
rized in Fig. 11.1 .
The sleep systems illustrated in Fig. 11.1 are controlled by three key
drivers that interact and collectively determine the duration, quality, and
efficiency of sleep. Two of these drivers are endogenous, referred to as
the circadian system and a homeostatic hourglass oscillator, while the third
is exogenous and the product of our societal temporal structure (e.g., school
and work times). Normal versus abnormal sleep has, in turn, a major impact
upon mood, cognition, and mental and physical health. These relationships
are summarized in Fig. 11.2 .
2. SLEEP AND CIRCADIAN RHYTHM DISRUPTION
ARISING FROM SOCIAL TIMING
As described above, efficient sleep depends upon complex biological
drivers in the form of the circadian system and the homeostatic hourglass
oscillator ( Fig. 11.2 ) . In real life, however, an additional critical factor—
social timing—influences sleep opportunities and thereby sleep duration,
quality, and efficiency, potentially resulting in sleep and circadian rhythm
disruption (SCRD). A large database ( 150,000 entries) has been
established on sleep-activity behavior in the general population 2 by using
an internet-based questionnaire (the Munich ChronoType Questionnaire,