WHAT IS SAD?
Seasonal Affective Disorder (SAD) is a specific type of recurring
depressive illness that manifests in an annual pattern, usually
from early-to-late fall and subsiding with the longer, sunnier
days of spring.1 Some people have the milder
form, called Subsyndromal-SAD (S-SAD), also called Winter Blues,
which causes minor problems in their lives but not the total
disruption that full-blown SAD causes.
This is the Winter-SAD subtype; another subtype is
Summer-SAD, which occurs in the spring & summer months.
Summer-SAD is much rarer than Winter-SAD, is less well
researched, and its cause is undetermined. Throughout this
website, unless otherwise noted, the term "SAD" refers
specifically to Winter-SAD.
Researchers have confirmed that specific biological changes within
the brain occur in response to different levels of bright light
exposure, and that these biochemical changes affect hormones and
neurotransmitters responsible for regulating our mood, energy,
sleep and appetite. In the majority of the population, these
changes are not troublesome; they simply cause minor variations in
their annual rhythms. For those with SAD, though, these changes
are profound enough to cause significant disruption to their
WHO GETS IT?
SAD affects both genders, and people of all ages. A small but
significant percentage of children are affected, with the
female-male ratio being about equal among this age group. In the
15-43 age group, however, women outnumber men by nearly 3.5 to 1.
After age 44, the number of women starts to decline and the gender
ratio again equalizes.2
The effect of latitude on the incidence of SAD has not been
determined conclusively. Numerous studies indicate that incidence
increases with higher latitude, but some other studies have either
failed to show any correlation or shown an opposite trend.3
Anyone deprived of regular sunlight exposure or adequate indoor
lighting can suffer from SAD symptoms. A series of rainy, overcast
days can trigger SAD even in the summertime.4
WHAT ARE THE SYMPTOMS?
SAD manifests itself in different ways in different people. The
typical symptoms include decreased mood and energy level, social
withdrawal, reduction in sex drive, anxiety, irritability, and
difficulty concentrating or being productive at work. The
"classic" SAD symptoms, which are considered atypical symptoms of
nonseasonal depression, are changes in sleeping patterns
(oversleeping and having poor sleep) and appetite changes
(increased appetite, carbohydrate cravings, and subsequent weight
In children and teenagers, the symptoms are slightly different
from those for adults. These symptoms include irritability, crying
spells, anxiety, fatigue, difficulty in getting out of bed for
school, and a lowering of grades and self-esteem. Because these
symptoms mirror the symptoms of laziness, Attention Deficit
Disorder (ADD), learning disabilities, or the stereotypical
behavior of teenagers, it is important for parents to note whether
these symptoms recur year after year during the fall and winter
months, and whether they go away in the spring.6
WHAT CAUSES IT?
Researchers aren't sure what causes SAD. Three main theories have
been put forth, and there is contrasting evidence both for and
against each of these theories: the Melatonin Hypothesis, the
Phase Shift Hypothesis, and the Serotonin Hypothesis.
The Melatonin Hypothesis argues that SAD is due to too much
melatonin being secreted in response to the long, dark days of
winter.7 Some studies have supported this
theory, while others have disputed it.8
Advocates of the Phase Shift Hypothesis, proposed in 1986, contend
that in patients with SAD, circadian rhythms [see Sleep &
Circadian Rhythm Disorders section] have been desynchronized to
the light-dark cycle, and that appropriately timed bright light
reverses SAD symptoms by realigning these rhythms. Again, there is
evidence on either side of the debate.9
In the Serotonin Hypothesis, the idea is that serotonin levels in
the brain are much lower during the winter months in patients with
SAD than they are either in people without SAD or in SAD patients
during the spring and summer months. This hypothesis came about
from researchers observing that SAD patients tend to feel
energized after carbohydrate consumption (which increases
serotonin levels), whereas people without SAD generally feel more
lethargic after eating carbohydrates.10 Whether
serotonin is 'the cause' of SAD or not, there is currently a wide
body of evidence to suggest that it does play a major role in the
Other neurotransmitters (dopamine and noradrenaline, for example)
may also be involved, as well as other hormones (thyroid,
corticotrophin-releasing hormone). The role of these other
neurotransmitters and hormones, though, requires further research.12
HOW IS IT TREATED?
Bright light is highly effective in treating SAD. According to the
Journal of the American Medical Association, "Treatment [for SAD]
with bright environmental light is generally a first-line
therapeutic approach."13 Four out of five people
with seasonal difficulties (either SAD or S-SAD) should expect to
benefit from bright light treatment.14
"Several qualitative review of the literature...have concluded
that light therapy, administered by fluorescent light boxes...is
an effective treatment for SAD, with response rates of 60% to
90%."15 According to Norman Rosenthal, former
Chief of Clinical Psychobiology at the National Institute of
Mental Health, "The most effective, practical, and best-studied
way of enhancing your environmental light is by means of a special
light fixture or light box, the most commonly used method for
administering light therapy.16
Other treatments that may be helpful include changes in diet and
exercise, stress management, sleep restriction, psychotherapy, and
1 Wesson, VA & AJ Levitt: Light treatment for
seasonal affective disorder. In: Seasonal Affective Disorder and
Beyond: Light Treatment for SAD and Non-SAD Conditions. Edited by
Lam, RW. Washington, DC: American Psychiatric Press, 1998, p 45.
2 Eagles, JM: Sociodemographic aspects. In:
Seasonal Affective Disorder. Practice and Research. Edited by
Partonen, T & A Magnusson. New York: Oxford University Press,
2001, pp 34-37.
3 Mersch, PPA: Prevalence from population
surveys. In: Seasonal Affective Disorder. Practice and Research.
Edited by Partonen, T & A Magnusson. New York: Oxford University
Press, 2001, pp 133-134.
4 Rosenthal, NE: Winter Blues: Seasonal
Affective Disorder - What It Is and How to Overcome It. (rev. ed.)
New York: Guilford Press, 1998, p 51.
5 Partonen, T & N Rosenthal: Symptoms and course
of illness. In: Seasonal Affective Disorder. Practice and
Research. Edited by Partonen, T & A Magnusson. New York: Oxford
University Press, 2001, p 13.
6 Rosenthal, NE, CJ Carpenter, SP James et al.:
Seasonal affective disorder in children and adolescents. Am J
Psychiatry, 143(3): pp 356-358, 1986.
7 Rosenthal, 1998, p 249.
8 Lam, RW & AJ Levitt (eds.): Canadian Consensus
Guidelines for the Treatment of Seasonal Affective Disorder.
Canada: Clinical & Academic Publishing, 1999, pp 42-43.
9 ibid, pp 43-45.
10 Rosenthal, 1998, p 251.
11 Lam, p 46.
12 ibid, pp 46-47 & 51.
13 Rosenthal, NE: Diagnosis and treatment of
seasonal affective disorder. JAMA, 270(22): p 2719, 1993(a).
14 Rosenthal, NE: Winter Blues: Seasonal
Affective Disorder - What It Is and How to Overcome It. New York:
Guilford Press, 1993(b), p 108.
15 Lam, p 65.
16 Rosenthal, 1998, p 105.
17 Rosenthal, 1998, pp 144-204.