Depression Articles

SAD - Risk Factors

Risk Factors

Attributes that may increase your risk of SAD 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 more likely to develop 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.

The causes of SAD are unknown, but research has found some biological clues: 

  • 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 associated with clinically significant depression symptoms.

Resource - National Institute of Mental Health