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Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder (SAD) is a type of depression that's related to changes in seasons. SAD begins and ends at about the same times every year, with symptoms often starting in the fall and continuing into the winter months, sapping energy and making individuals feel moody. Less often, SAD causes depression in the spring or early summer. In either case, symptoms may start out mild and become more severe as the season progresses.

This yearly feeling may be mistaken as simply a case of the "winter blues" or a seasonal funk.

Major depression

SAD is a subtype of major depression and the symptoms are similar, such as:

  • Feeling depressed most of the day, nearly every day;
  • Feeling hopeless or worthless;
  • Having low energy;
  • Losing interest in activities once enjoyed;
  • Having problems with sleeping;
  • Experiencing changes in appetite or weight;
  • Feeling sluggish or agitated;
  • Having difficulty concentrating;
  • Having frequent thoughts of death or suicide.

Fall and winter SAD

Symptoms specific to winter-onset SAD, sometimes called winter depression, may include:

  • Irritability;
  • Tiredness or low energy;
  • Problems getting along with other people;
  • Hypersensitivity to rejection;
  • Heavy, "leaden" feeling in the arms or legs;
  • Oversleeping;
  • Appetite changes, especially a craving for foods high in carbohydrates;
  • Weight gain.

Spring and summer SAD

Symptoms specific to summer-onset SAD, sometimes called summer depression, may include:

  • Depression;
  • Trouble sleeping (insomnia);
  •  Weight loss;
  • Poor appetite;
  • Agitation or anxiety.

Seasonal changes in bipolar disorder
In some people with bipolar disorder, spring and summer can bring on symptoms of mania or a less intense form of mania (hypomania), and fall and winter can be a time of depression.

Take signs and symptoms of seasonal affective disorder seriously. As with other types of depression, SAD can get worse and lead to problems if it's not treated.

These can include:

  • Suicidal thoughts or behaviour;
  • Social withdrawal;
  • School or work problems;
  • Substance abuse.

When to see a doctor

Though it is normal to have days when you feel down, if this persists, sleep patterns and appetites have changed or if you are feeling hopeless, thinking about suicide, or turning to alcohol for comfort or relaxation it is time to consider getting medical help.

Ontario Shores has several service areas providing treatment for individuals experiencing depression. Learn more... 


The specific cause of SAD remains unknown. Some suggested factors include:

  • Your biological clock (circadian rhythm). The reduced level of sunlight in fall and winter may cause winter-onset SAD. This decrease in sunlight may disrupt your body's internal clock and lead to feelings of depression.
  • Serotonin levels. A drop in serotonin, a brain chemical (neurotransmitter) that affects mood, might play a role in SAD. Reduced sunlight can cause a drop in serotonin that may trigger depression.
  • Melatonin levels. The change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood.

Risk factors

Factors that may increase your risk of seasonal affective disorder include:

  • Being female. SAD is diagnosed more often in women than in men, but men may have more-severe symptoms.
  • Age. Young people have a higher risk of winter SAD, and winter SAD is less likely to occur in older adults.
  • Family history. People with SAD may be more likely to have blood relatives with SAD or another form of depression.
  • Having clinical depression or bipolar disorder. Symptoms of depression may worsen seasonally if you have one of these conditions.
  • Living far from the equator. SAD appears to be more common among people who live far north or south of the equator. This may be due to decreased sunlight during the winter and longer days during the summer months.


The treatment for SAD may include light therapy (phototherapy), psychotherapy and medications.

Treatment can help prevent complications, especially if SAD is diagnosed and treated before symptoms worsen.

* Adapted from various internet sources including WebMD, PsychCentral and CMHA

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