Difference Between Seasonal Affective Disorder and Depression

Seasonal Affective Disorder (SAD) and depression are both mental health disorders that can affect a person's mood, energy levels, and overall well-being. However, there are significant differences between the two, particularly in their causes, symptoms, and treatment options.

What is Seasonal Affective Disorder?

Seasonal Affective Disorder (SAD) is a type of depression that typically occurs during the fall and winter months when there is less daylight. This disorder affects around 5% of the population, and it is more common in women than in men.

The exact cause of SAD is not yet known, but it is believed to be linked to the body's natural response to light and darkness. Specifically, reduced exposure to sunlight can disrupt the body's internal clock, which can lead to changes in the production of hormones such as melatonin and serotonin. This disruption can cause a range of symptoms, including fatigue, irritability, sleep disturbances, and decreased interest in social activities.

  • Diagnosis − The doctor will perform a physical exam and test the thyroid to exclude this as a possible cause for the symptoms. A psychologist can also perform an assessment and determine if the person matches the criteria for seasonal affective disorder as listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V).

  • Causes − The drop in sunlight during winter is thought to play a role in some cases in causing seasonal affective disorder. The other causes involve changes in the levels of the hormone melatonin and also in levels of the neurotransmitter serotonin due to these changes in seasons. There also seems to be genetic factors that are also important in causing the illness.

  • Risk factors − There does seem to be some genetic basis for the development of seasonal affective disorder, since some genes have been found that are linked to the condition. A risk factor is also living at high and low latitudes that are distant from the equator. This is because the change in seasons is more pronounced the further from the equator a person is.

  • Treatment − Sometimes therapy such as psychotherapy and cognitive behavioral therapy can help individuals who have SAD. In other cases, patients may be prescribed medications such as antidepressants, for instance Wellbutrin or Aplenzin. Light therapy is often the first choice for winter SAD. In this therapy the person is exposed to more light by sitting by an artificial light source that mimics natural daylight.

What is Depression?

Depression, on the other hand, is a mental health disorder that can occur at any time of the year and affects around 7% of the population. Unlike SAD, depression can be caused by a wide range of factors, including genetic, environmental, and psychological factors. Depression can also be triggered by traumatic life events, such as the loss of a loved one, a job loss, or a divorce.

The symptoms of depression are similar to those of SAD, but they can be more severe and longer-lasting. Symptoms of depression include feelings of sadness or hopelessness, loss of interest in previously enjoyable activities, changes in appetite or sleep patterns, and thoughts of suicide.

  • Diagnosis − A physical exam needs to be done and tests to eliminate possible physical diseases that could be manifesting as depressive symptoms. Psychologists can evaluate a person to see if they match the criteria as outlined in the DSM-5 book.

  • Causes − The condition does appear to be genetic and inherited to some extent, with about 50% of people having a relative who experienced the mood disorder. Depression is thought to result from a combination of certain genetic and environmental factors and one idea is that the neurotransmitters in the brain become unbalanced causing the disorder. Major life problems such as death of a loved one or divorce can be precipitating factors resulting in depression.

  • Risk factors − Women and people who have relatives who have had depression are at increased risk of the disorder. Individuals prone to anxiety seem to also be at higher risk for depression. The presence of other mental problems can also be a risk factor, for instance individuals who have bipolar disorder often have episodes of depression. Pregnancy can be a risk factor in some women who suffer post-partum depression due to hormonal changes.

  • Treatment − Treatment options for depression include various types of psychological therapy and medications. Medications such as selective serotonin reuptake inhibitors (SSRIs) are one commonly prescribed type of medicine. There are other types such as heterocyclic antidepressants which may be tried if the SSRIs do not work for a particular patient. In some cases, patients may find support groups helpful. Patients may need to stay on medication long-term though, depending on their condition.

Differences: Seasonal Affective Disorder and Depression

One key difference between SAD and depression is the timing of their onset. SAD typically starts in the fall or winter and disappears in the spring or summer, while depression can occur at any time and may last for weeks or months. Another difference is the severity of the symptoms.

While both disorders can cause fatigue, low mood, and changes in sleep and appetite, the symptoms of depression are typically more severe and may include feelings of worthlessness or suicidal ideation. Additionally, SAD tends to affect people who live in northern latitudes, where there is less daylight in the winter months, while depression is more prevalent worldwide.

Treatment options for SAD and depression differ as well. For SAD, light therapy is a common treatment option. This involves sitting in front of a lightbox that emits bright light for 30 minutes to an hour each day. The light mimics natural daylight and helps to regulate the body's internal clock. Other treatments for SAD may include cognitive-behavioral therapy, antidepressant medication, or changes to one's diet and exercise routine.

For depression, treatment options include antidepressant medication, psychotherapy, or a combination of both. Antidepressant medication works by altering the levels of neurotransmitters in the brain that are involved in mood regulation. Psychotherapy, on the other hand, involves talking with a mental health professional to identify and address underlying psychological issues that may be contributing to the depression.

The following table highlights the major differences between Seasonal Affective Disorder and Depression −


Seasonal Affective Disorder



Seasonal affective disorder is a condition in which a person feels sad during a specific season of the year.

Depression is a condition in which the person’s symptoms impact their ability to function.


Seasonal affective disorder is always linked to the season of the year.

Depression is not always linked to particular seasons of the year.

Due to hormones of pregnancy

The condition of seasonal affective disorder is never due to changing hormones during pregnancy.

The disorder of depression can sometimes be due to changing hormones during pregnancy.


The causes of seasonal affective disorder are largely thought to be a combination of genes that were inherited and a change in the seasons.

The causes of depression are believed to be genetics, possibly neurotransmitter imbalances, and due to major life problems.

Risk factors

Having a family member with the condition and living far from the equator are risk factors for SAD.

Having a relative with depression and being female or having another mental disorder, are risk factors for developing depression.


The treatment for SAD is light therapy, medication and sometimes psychological counseling.

The treatment for depression is medication and psychological counseling.


In conclusion, while SAD and depression share some common symptoms, they are distinct disorders with different causes, timing, severity, and treatment options. Understanding these differences is important for accurate diagnosis and effective treatment of these conditions.

Updated on: 26-Apr-2023


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