University of Iowa Adult Outpatient Psychiatry
(319) 353-6314. After hours: (319) 356-1616
February 12, 2016
SEASONAL AFFECTIVE DISORDER
Seasonal affective disorder (SAD) is commonly referred to as winter depression in the northern hemisphere,
but also occurs in the southern hemisphere during their winter. Patients with SAD consistently develop
depression during the winter months, remitting (no symptoms) during the summer. While depressive episodes
may occur during the summer months, winter episodes far outnumber summer episodes. Some people even
develop hypomanic or manic symptoms during the spring and summer (increased activity, poor sleep,
impulsive behavior, etc.).
Symptoms characteristic of SAD include fatigue, oversleeping, overeating with weight gain and craving for
carbohydrates, avoidance of social situations, sensitivity to rejection, heavy feeling in the arms or legs, poor
concentration, difficulty completing tasks, and irritability. Many patients begin to notice symptoms as the days
shorten, with January and February typically the worse months. Symptoms begin to improve as days lengthen.
The illness tends to begin when patients are in their early to mid twenties, with more women than men
developing SAD (4:1).
Phototherapy: Lights should provide 10,000 lux (approximately ten 100-watt incandescent bulbs). Most
people use the light for 30 - 90 minutes. Begin with 10-15 minute sessions, and gradually increase to 30-45
minutes a day. Light therapy works best when used early in the morning, especially when it is still dark
outside, but can be used twice daily. Additional light exposure during the afternoon may be helpful for patients
who do not respond as well to morning-only use, or who notice significant symptoms in the late afternoon and
early evening, especially fatigue and sleepiness. The light source should generally be within 2 feet of the eyes,
depending on the light (your light should list the length at which 10,000 lux is obtained). You should not look
directly into the light, but your eyes must be open for light to be effective. Most professionally-built lights
have diffusers that block UVa and UVb light, to decrease risk of skin or eye damage. There does not appear to
be any differences in effectiveness among various wavelengths of light used. Tanning beds are ineffective and
can be dangerous because of the UV light used. When used to treat depression, light therapy generally takes 24 days to become effective, with remission usually occurring within 2-4 weeks. Most people with SAD use
light therapy daily during the winter, starting around late September or early October.
Most people use lights specifically designed for phototherapy, but some have found 4-lamp fluorescent
light fixtures just as effective. Some have also found exposure to an hour of sunlight early in the morning
(especially with a good walk) as effective as a light box.
Too much light exposure may lead to irritability, inability to sleep, especially awakening too early in the
morning, feeling “wired,” headache, eyestrain, nausea, and overactivity, but rarely results in any significant
problems. The most common side effect is eye irritation, which often responds to increasing the humidity in
the house, or sitting farther away from the light. There has been no evidence of long-term damage to the eyes
from light therapy. Do not take St.John’s wort when using phototherapy, as a rash may occur.
There are other treatments which can be effective for people with SAD who do not or only partially
respond to light therapy. Please contact your physician if depressive symptoms appear or persist despite use of
light.
Additional resources: Winter Blues by Norman Rosenthal (Guilford Press), Seasonal Affective Disorder, by
Angela Smyth (Harper Collins Publishers).
Local Vendors of Light Boxes
Stress Reduction Systems
338-5246
Manufactured and distributed locally.
The following companies provide high intensity/full spectrum lights (addresses obtained off the internet):
The SunBox Co.
19217 Orbit Dr.
Gaithersburg MD 20879
(800) LITE-YOU
www.sunbox.com
Northern Light Technologies
8971 Henri Bourassa West
Montreal Canada H45 1P7
800-263-0066
www.alaskanorthernlights.com
Apollo Light Systems Inc.
352 West 1060 South
Orem UT 84058
(800) 545-9667
www.lighttherapy.com
The Litebook Co
http://www.litebook.com/usa/index.htm
Up-Lift Phototherapy light
http://www.up-lift.com/section/lighttherapy.html
Other sources of information:
Seasonal Studies Program
National Institute of Mental Health
Building 10, Room 4S-239
9000 Rockville Pike
Bethesda MD 20892
(301) 496-2141
National Organization for Seasonal Affective
Disorders (NOSAD)
PO Box 40190
Washington DC 20016
National Depressive and Manic Depressive
Association (NDMDA)
730 N Franklin Suite 501
Chicago IL 60610
800-826-3632
Society for Light Treatment and Biological
Rhythms
10200 W 44th Ave, Suite 304
Wheat Ridge CO 80033-2840
(303) 424-3697