SAD: Seasonal Affective Disorder

Seasonal Affective Disorder (SAD) is a type of depression that comes and goes with the seasons, typically starting in the late fall and early winter and going away during the spring and summer. Depressive episodes linked to the summer can occur, but are much less common than winter episodes of SAD.

Seasonal Affective Disorder (SAD) is not considered as a separate disorder. It is a type of depression displaying a recurring seasonal pattern. To be diagnosed with SAD, people must meet full criteria for major depression coinciding with specific seasons (appearing in the winter or summer months) for at least 2 years. Seasonal depressions must be much more frequent than any non-seasonal depressions.

Symptoms of major depression:
• Feeling depressed most of the day,
nearly every day
• Feeling hopeless or worthless
• Having low energy
• Losing interest in activities you once
• Having problems with sleep
• Experiencing changes in your appetite
or weight
• Feeling sluggish or agitated
• Having difficulty concentrating
• Having frequent thoughts of death or

Symptoms of the winter SAD:
• Having low energy
• Hypersomnia
• Overeating
• Weight gain
• Craving for carbohydrates
• Social withdrawal (feel like “hibernating”)

Symptoms of summer SAD:
• Poor appetite with associated weight
• Insomnia
• Agitation
• Restlessness
• Anxiety

• Episodes of violent behavior

Risk factors may include:
• Being female. SAD is diagnosed four
times more often in women than men.
• Living far from the equator. SAD is more
frequent in people who live far north or
south of the equator. For example, 1
percent of those who live in
Florida and 9 percent of
those who live in New
England or Alaska
suffer from SAD.
• Family history.
People with
a family
history of
other types
of depression are
likely to
SAD than
people who
do not have
a family history of depression. • Having depression
or bipolar disorder. The
symptoms of depression
may worsen with the seasons if
you have one of these conditions (but
SAD is diagnosed only if seasonal depressions are the most common).
• Younger Age. Younger adults have a
higher risk of SAD than older adults.
SAD has been reported even in children
and teens.
People with SAD may have trouble
regulating one of the key neurotransmitters involved in mood, serotonin. One
study found that people with SAD have 5
percent more serotonin transporter protein
in winter months than summer months.
Higher serotonin transporter protein leaves
less serotonin available at the synapse
because the function of the transporter is

to recycle neurotransmitter back into the
pre-synaptic neuron.
People with SAD may overproduce the
hormone melatonin. Darkness increases
production of melatonin, which regulates
sleep. As winter days become shorter,
melatonin production increases, leaving
people with SAD to feel sleepier and more
lethargic, often with delayed
circadian rhythms.
People with SAD also
may produce less
Vitamin D. Vitamin
D is believed to
play a role in
serotonin activity. Vitamin
D insufficiency may be
with clinically significant


There are four major types of treatment for SAD: Medication, light therapy, psychotherapy, and vitamin D. These may be used alone or in combination.

Medication: Selective Serotonin Reuptake Inhibitors (SSRIs) are used to treat SAD. The FDA has also approved the use of bupropion, another type of antidepressant, for treating SAD.

As with other medications, there are side effects to SSRIs. Talk to your doctor about the possible risks of using this medication for your condition. You may need to try several different antidepressant medications before finding the one that improves your symptoms without causing problematic side effects. For basic information about SSRIs and other mental health medications, visit NIMH’s Medications webpage. Check the FDA’s website for the latest information on warnings, patient medication guides, or newly approved medications.

Light Therapy: Light therapy has been a mainstay of treatment for SAD since the 1980s. The idea behind light therapy is to replace the diminished sunshine of the fall and winter months using daily exposure to bright, artificial light. Symptoms of SAD may be relieved by sitting in front of a light box first thing in the morning, on a daily basis from the early fall until spring. Most typically, light boxes filter out the ultraviolet rays and require 20-60 minutes of expo – sure to 10,000 lux of cool-white fluorescent light, an amount that is about 20 times greater than ordinary indoor lighting.

Psychotherapy: Cognitive behavioral therapy (CBT) is type of psychotherapy that is effective for SAD. Traditional cognitive behavioral therapy has been adapted for use with SAD (CBT-SAD). CBT-SAD relies on basic techniques of CBT such as identifying negative thoughts and replacing them with more positive thoughts along with a technique called behavioral activation. Behavioral activation seeks to help the person identify activities that are engaging and pleasurable, whether indoors or outdoors, to improve coping with winter.

Vitamin D: At present, vitamin D supplementation by itself is not regarded as an effective SAD treatment. The reason behind its use is that low blood levels of vitamin D were found in people with SAD. The low levels are usually due to insufficient dietary intake or insufficient exposure to sunshine. However, the evidence for its use has been mixed. While some studies suggest vitamin D supplementation may be as effective as light therapy, others found vitamin D had no effect.

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