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What Causes Seasonal Affective Disorders

What Causes Seasonal Affective Disorders

If you get moody or mildly depressed when the seasons change, you’re not alone. Symptoms like fatigue and depression could be symptoms of something called seasonal affective disorder. But this condition can be managed; you may find relief with certain kinds of therapy, as well as newer options including ketamine therapy.


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. If you’re like most people with SAD, your symptoms start in the fall and continue into the winter months, sapping your energy and making you feel moody. Less often, SAD causes depression in the spring or early summer.” Fortunately, many symptoms can be managed with treatment like ketamine therapy.


SAD is a kind of depression, not a unique disorder. People who get seasonal affective disorder may show these signs of depression:

  • Sadness
  • Anxiety
  • Carbohydrate desires and weight gain
  • Severe fatigue and low energy
  • Feelings of worthlessness or hopelessness
  • Trouble concentrating
  • Irritability
  • Limbs feeling heavy
  • Lack of interest in normal activities and social interactions
  • Sleeping more
  • Thoughts of suicide or death

It may include restlessness and agitation, anxiety, lack of appetite, weight loss, and digestive problems.


According to MedlinePlus, seasonal affective disorder happens in anywhere from less than one percent to three percent of people in the overall population. This means it harms 10 to 20 percent of people experiencing major depressive disorder and nearly 25 percent of those with bipolar disorder.

Some people also have subsyndromal seasonal affective disorder or seasonality, which affects a greater number than SAD. These people experience mild changes in mood that relate to changes in seasons.


As is the case with many kinds of mental illness and chronic pain conditions, researchers don’t know precisely what causes SAD. The absence of sunlight can trigger the condition in people who are already at risk of getting it. Other possibilities:

  • Biological clock shift: If you have less exposure to sunlight, your biological clock shifts. This internal clock controls mood, sleep, and hormones. When it gets disrupted, people may have problems regulating their moods.
  • Brain chemical imbalance: Brain chemicals known as neurotransmitters transmit communications between nerves. These chemicals contain serotonin, which contributes to sensations of happiness. People with chances of SAD may already present less serotonin activity. Because sunlight helps adjust serotonin, the absence of the winter sun can worsen the situation. Serotonin levels can fall even more, resulting in mood changes.
  • Vitamin D deficiency: Serotonin also gets a lift from vitamin D. Because sunlight helps us generate vitamin D, less sun during the winter can result in a vitamin D deficiency. That shift is known to impact serotonin and mood.
  • Melatonin boost as it relates to sleep patterns: The absence of sunlight for several months of the year can stimulate an abundance of melatonin in certain people. They may feel sleepy and sluggish during the dark, colder winter months.
  • Negative thoughts: People with seasonal affective disorder often suffer from higher levels of stress, anxiety, and negative opinions about the winter than other people. And researchers don’t know for certain if these thoughts are a trigger or byproduct of seasonal depression.


To assist in diagnosing SAD, your doctor or mental healthcare provider may complete a thorough evaluation, which normally includes:

  • A physical exam. Your doctor may perform a physical exam and inquire in-depth about your health. In some instances, depression can be linked to an unknown physical health condition.
  • Lab tests. In this case, your doctor may perform a blood test known as a complete blood count or check your thyroid to ensure it’s working properly.
  • A psychiatric evaluation. To confirm signs of depression, your doctor or mental health provider will ask about your behavior patterns, feelings, symptoms, and thoughts. You may be asked to complete a questionnaire to help provide answers to these questions.
  • Consultation with the DSM-5. Your mental healthcare provider may refer to the criteria for seasonal depressive disorders described in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), put out by the American Psychiatric Association.


Not everyone is affected by less sunlight during the fall and winter. Some people just roll with seasonal changes, while others may struggle a little bit more with mood changes, fatigue, sleep patterns, and other symptoms often associated with seasonal affective disorder. Certain kinds of treatment, like light therapy, may help but more people are turning to ketamine treatment to help manage symptoms than ever before.

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