156 ChapTER 5 Body Rhythms and Mental States
blame. “There should be sanctioned on-shift nap-
ping. That’s the way to handle night-shift work,”
said one neuroscientist. But the Federal Aviation
Administration still bans the practice, while call-
ing for more data.
One reason a simple cure for desynchroniza-
tion has so far eluded scientists is that circadian
rhythms can be affected by illness, stress, exer-
cise, drugs, mealtimes, and many other factors.
Also, circadian rhythms can differ greatly from
individual to individual. There truly are morn-
ing people (“larks”) and evening people (“owls”).
Scientists call your disposition to be a lark or owl
your chronotype. Genetic influences may contrib-
ute to chronotypes, although attempts to find
“chronotype genes” have proven difficult to repli-
cate (Chang et al., 2011; Osland et al., 2011). Your
chronotype may change as you age: Adolescents
are more likely than children and older adults to
be owlish (Biss & Hasher, 2012), which may be
why many teenagers have trouble adjusting to
school schedules.
You may be able to learn about your own
chronotype and biological rhythms through care-
ful self-observation, and you may want to try put-
ting that information to use when planning your
daily schedule.Moods and Long-Term Rhythms
LO 5.3, LO 5.4
According to Ecclesiastes, “To every thing there
is a season, and a time for every purpose under
heaven.” Modern science agrees: Long-term
cycles have been observed in everything from
the threshold for tooth pain to conception rates.
Folklore holds that our moods follow similar
rhythms, particularly in response to seasonal
changes and, in women, menstrual changes. But
do they?Does the Season Affect Moods? Clinicians
report that some people become depressed during
particular seasons, typically winter, when periods
of daylight are short, a phenomenon that has comechronotype A person’s
disposition to be a
“morning person” or an
“evening person.”
to be known as seasonal affective disorder (SAD).
During the winter months, patients report feel-
ings of sadness, lethargy, drowsiness, and a craving
for carbohydrates. To counteract the effects of
sunless days, physicians and therapists often treat
them with phototherapy, having them sit in front
of bright fluorescent lights at specific times of the
day, usually early in the morning. Some physicians
also prescribe antidepressants and other drugs.
Unfortunately, much of the research on the
effectiveness of light treatments has been flawed;
a review of 173 published studies found that only
20 had used an acceptable design and suitable
controls (Golden et al., 2005). But a meta-analysis
of the data from those 20 studies did throw some
light on the subject, so to speak. When people
diagnosed with SAD were exposed to either a
brief period (e.g., 30 minutes) of bright light after
waking or to light that slowly became brighter,
simulating the dawn, their symptoms were in fact
reduced. Light therapy even helps people with
mild to moderate nonseasonal depression (Pail
et al., 2011).
SAD may occur in people whose circadian
rhythms are out of sync; in essence, they have a
chronic form of jet lag (Lewy et al., 2006). They
may also have some abnormality in the way theyseasonal affective
disorder (SAD) A dis-
order in which a person
experiences depression
during the winter and an
improvement of mood in
the spring.
This woman reads and drinks tea for at least 15 minutes
a day in front of what she calls her “happy light,” which
she uses for seasonal depression.Get Involved! Measuring Your Alertness Cycles
For at least three days, except when you are sleeping, keep an hourly record of your mental alertness level,
using this five-point scale: 1 = extremely drowsy or mentally lethargic, 2 = somewhat drowsy or mentally
lethargic, 3 = moderately alert, 4 = alert and efficient, 5 = extremely alert and efficient. Does your alertness
level appear to follow a circadian rhythm, reaching a high point and a low point once every 24 hours? Or
does it follow a shorter rhythm, rising and falling several times during the day? Are your cycles the same
on weekends as during the week? Most important, how well does your schedule mesh with your natural
fluctuations in alertness?