Key takeaways

  • Changes in sunlight exposure during different seasons can disrupt the body’s circadian rhythm, potentially triggering manic episodes in spring and summer and depressive episodes in autumn and winter.
  • Other meteorological factors like temperature and solar radiation have been linked to bipolar disorder, with higher temperatures and solar radiation correlating with increased psychiatric emergency admissions.
  • Seasonal affective disorder (SAD), which is more prevalent in those with bipolar II disorder, can cause depressive symptoms during colder months or, less commonly, manic symptoms during warmer months, necessitating tailored treatment plans.

Bipolar disorder is a mental health condition characterized by large mood changes from periods — or episodes — of high energy and mania to periods of low mood and depression.

If you have bipolar disorder, seasonal changes may affect shifts in mood due to the impacts of certain environmental and social factors on your hormones, body temperature, and circadian rhythm, which is often referred to as your biological clock.

Episodes of mania and depression may be impacted differently by seasonal changes.

However, knowing how the seasons and other environmental factors affect bipolar symptoms can help you better manage your condition.

Your circadian rhythm is powered by the suprachiasmatic nucleus in the brain. This part of the brain regulates physiological circadian rhythms by detecting levels of sunlight and processing other environmental factors.

People with bipolar disorder may have altered circadian and seasonal rhythms and sometimes demonstrate seasonal patterns of depressive and manic episodes.

For instance, a 2025 review found that episodes of mania were associated with seasonal shifts into spring and summer, while depressive episodes were more common in autumn and winter.

Spring and summer are typically characterized by longer periods of sunlight, while autumn and winter have longer periods of darkness.

Similarly, in a 2021 review of 51 studies, researchers found a few patterns:

  • Hospital admissions for bipolar depressive episodes peaked in early winter.
  • Hospitalizations for manic episodes are more common in spring and summer.
  • Seasonal variations were more common in women with bipolar disorder.

A 2021 analysis of 4,876 people with bipolar I disorder from 71 different geographic locations found that higher rates of suicide attempts were present in locations farther from the equator.

These locations experience greater solar variability, meaning the amount of solar radiation shifts drastically throughout the year.

Help is available

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

  • Call or text the 988 Suicide and Crisis Lifeline at 988 or chat at 988lifeline.org. Caring counselors are available to listen and provide free and confidential support 24/7.
  • Text HOME or HOLA to the Crisis Text Line at 741741 to connect with a volunteer crisis counselor for free and confidential support 24/7.
  • Not in the United States? Find a helpline in your country with Befrienders Worldwide.
  • Call 911 or your local emergency services number if you feel safe to do so.

In addition to sunlight, a 2020 study found that other meteorological factors can have an effect on bipolar disorder, including:

  • minimum and maximum temperatures
  • rainfall
  • cloudiness
  • atmospheric pressure

A 2019 study found that more people with bipolar disorder were admitted to the emergency psychiatric ward on days with higher temperatures and higher solar radiation.

Seasonal affective disorder (SAD) is a type of depressive disorder that typically occurs with seasonal changes, most commonly during the colder, darker months of the year.

SAD is more common in individuals with bipolar disorder, specifically bipolar II disorder, which is characterized by frequent depressive episodes and hypomania.

Some possible causes of SAD include:

  • reduced serotonin
  • too little sunlight
  • altered melatonin levels

An older 2017 study also found that photoperiod — the period of time each day when a person is exposed to light — is a key element in bipolar disorder.

The researchers found that people with bipolar disorder were hospitalized for depression in winter, when exposure to light is reduced due to shorter days.

On the other hand, summer-pattern SAD can affect the moods of people with bipolar disorder during the sunnier, warmer months.

The same 2017 study found that more people were hospitalized for mania in spring and summer when daylight exposure is highest throughout the year.

Treating SAD

If you have SAD, treatment may include:

A healthcare professional can help develop an appropriate treatment plan tailored to your individual needs.

Lifestyle habits, like getting regular exercise and sun exposure, may also help manage SAD symptoms.

Several environmental, social, physical, and emotional factors can impact mood shifts if you’re living with bipolar disorder, and these will differ from person to person.

The primary aspect of symptom management is to follow your treatment plan, which may include a combination of lifestyle habits and medications.

Some treatments may also focus on managing bipolar disorder mood shifts influenced by seasonal changes.

Managing seasonal bipolar depression

Light therapy is recommended by the International Society of Bipolar Disorders as a treatment for acute bipolar depression, but clinical trials on the therapy are limited.

A small 2020 trial in 58 people found that 55% experienced remission of depressive symptoms after receiving light therapy using a lamp for 30 minutes during morning hours for 7 to 21 days.

However, two people in the study experienced hypomanic episodes while undergoing light therapy.

A 2020 review of studies also found that light therapy had a significant antidepressant effect in individuals with bipolar disorder.

However, none of these studies investigated the effects of light therapy on manic symptoms or the recurrence of mood episodes.

More recently, a 2025 review found that light therapy may increase the risk of manic symptoms and manic episodes.

More robust research is needed to verify the effect of light therapy on bipolar disorder. As such, it’s critical to speak with a psychiatrist before adding it to your treatment plan.

Managing seasonal mania

According to the National Institute of Mental Health, fewer studies have examined possible treatment methods for summer-pattern SAD.

However, understanding how seasonal changes may impact the disorder is a start.

Individuals with summer-pattern SAD may have reduced melatonin levels, which can lead to:

However, keep in mind that these symptoms have not been researched.

Healthy sleep habits, consistency with prescribed medications and other treatments, and stress reduction strategies can help prevent manic episodes during the hot summer months.

Medical Perspective

“If you notice a pattern to your seasonal mood changes, speak with your psychiatrist about developing a medication strategy that may help prevent seasonal mood episodes.

Adhering fairly tightly to your typical sleep and dietary routines can also help prevent sharp changes from negatively affecting your mood.

Always discuss any strategies with your psychiatrist to prevent mistakenly doing something that could negatively affect your mood.”

— Nicole Washington, DO, MPH

Learn more about alternative treatments for managing bipolar disorder.

Quotes represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Bipolar disorder symptoms can follow a seasonal pattern. You may experience more depressive moods in the winter or darker months and be at higher risk for mania in the summer and spring.

Being aware of changes in your circadian rhythm and seasonal symptoms can help you and your healthcare professional manage bipolar depression.