What You Need to Know About This Groundbreaking Study
As a clinical psychologist, I have been working with psychiatrists treating bipolar disorder for over 14 years. Over that period, I, as well as many of my colleagues, would tell you that we notice mood episodes occur more frequently during certain times of the year. For example, maybe depression hits harder in the winter months, or we notice that manic episodes tend to flare up in spring. Turns out that our observations are now supported by new research.
What Is Bipolar Disorder?
I have a whole section dedicated to Bipolar Disorder, and how I treat this issue, but just so we are all on the same page, let me briefly define Bipolar Disorder. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), bipolar disorder is characterized by periods of deep, prolonged, and profound depression that alternate with periods of an excessively elevated or irritable mood known as mania.
Manic episodes are characterized by at least 1 week of profound mood disturbance, marked by elation, irritability, or expansiveness. People with Bipolar Disorder experience periods of depression (feeling very sad, hopeless, or empty) and periods of mania or hypomania (feeling unusually energetic, euphoric, or irritable).
Current statistics show that about 2.8% of American adults, or roughly 7 million people, live with bipolar disorder, and it can affect people of all ages, backgrounds, and walks of life. I have more on my Bipolar Disorder page.
The Seasonal Connection
As I mentioned at the beginning, researchers and clinicians have long suspected that seasons might play a role in bipolar disorder, but until now, no one had studied it thoroughly. This new research, involving over 1,700 patients, provides us with clear answers.
Here’s what they discovered: 1 in 4 people with bipolar disorder experience seasonal patterns – meaning their mood episodes happen more frequently or severely during specific times of the year (Ercis et al., 2025).
Why Temperature Matters
Before diving into the specific seasonal patterns, it’s important to understand that it’s not just about seasons themselves – daily temperature changes directly affect mood symptoms. Another study looking into how temperature and mood tracked over 6,000 people and found that each 1°C (about 1.8°F) increase in temperature:
- Reduces depression symptoms by 0.2%
- Increases mania symptoms by 0.4%
This helps explain why seasonal patterns exist – your brain is literally responding to changes in temperature. Spring has the strongest effect on depression (warmer weather lifting mood), while autumn has the strongest effect on mania (temperature changes triggering episodes) (Clery et al., 2025).
Interestingly, what matters most isn’t the absolute temperature, but how different it is from what you’re used to. In other words, an unusually warm day in winter might affect you more than the same temperature in summer.
Four Types of Seasonal Patterns
The researchers identified four distinct patterns:
1. Fall-Winter Depression
These patients tend to experience their worst depressive episodes during the colder, darker months. Think of it as an extreme version of the “winter blues” that many people feel.
2. Spring-Summer Hypomania
These individuals are more likely to have manic or hypomanic episodes (periods of elevated mood and energy) during warmer, brighter months.
3. Winter-Summer Swing
Some people experience both patterns – depression in fall and winter, followed by hypomania in spring and summer.
4. Indeterminate Seasonality
This category includes people who have seasonal patterns that don’t fit neatly into the other groups.
The Game-Changing Discovery
Here’s the most important finding: the type of seasonal pattern you have may predict how well certain medications will work for you.
Fall-Winter Depression: The Treatment Challenge
People with fall-winter depression patterns showed something concerning – they were much more likely to have poor responses to lithium and other mood stabilizers for managing their mood episodes (Ercis et al., 2025). Lithium is often considered the “gold standard” medication for bipolar disorder, so this finding was surprising to researchers.
This pattern may be partly explained by temperature research: these individuals are missing the mood-lifting effects of warmer temperatures during colder months, making their depression more severe and harder to treat (Clery et al., 2025).
According to researchers Ercis et al.(2025), these patients also:
- Used more antidepressants throughout their lives.
- Required more psychiatric medications overall.
- Had their first bipolar episode at a younger age.
Spring-Summer Hypomania: The Better Outcomes
In contrast, people with spring-summer hypomania patterns had some advantages:
- They were less likely to experience rapid cycling (four or more mood episodes per year)
- They needed fewer antidepressants over their lifetime
- Their condition seemed somewhat more manageable
Rapid cycling means having four or more mood episodes within a single year, like going from depression to mania and back again multiple times, rather than having just a few longer episodes. This creates a roller coaster effect that’s harder to manage and treat.
However, temperature research suggests that these individuals may be more sensitive to heat, which can trigger manic symptoms, especially during heat waves or unusually warm weather.
The Life-Saving Context You Need to Know
Here’s where the story gets more complex, and why you should never make medication decisions without consulting your physician first.
While some people with fall-winter depression may not respond as well to lithium for mood episodes, recent research involving over 100,000 patients shows that lithium reduces suicide risk by 50% in people with bipolar disorder (Lee et al., 2025).
This is huge! Suicide is one of the most serious risks for people with bipolar disorder, and lithium provides crucial protection even if it doesn’t perfectly control mood episodes. There are other mood stabilizers available, but they reduce suicide risk by about 30% according to the same study.
This creates a complex treatment puzzle: your seasonal patterns might predict that lithium won’t work perfectly for your mood episodes, but it could still be saving a life in ways you can’t see.
What This Means for Individuals with Bipolar Disorder
If You Have Bipolar Disorder
Start paying attention to when your mood episodes occur. Keep a simple calendar or use a mood tracking app to note:
- When depressive episodes begin and end
- When manic or hypomanic episodes happen
- Daily temperature and weather conditions
- Any patterns you notice with heat waves, cold snaps, or unseasonably warm/cold days
- Any patterns you notice over several months or years
This information could be incredibly valuable for your treatment team.
Practical Weather Strategies
- For depression-prone periods: Consider spending time outdoors during warmer, sunny days (while being mindful of medication side effects in heat)
- For mania-prone periods: Prepare for hot weather with cooling strategies, air conditioning, and extra symptom monitoring
- For extreme weather: Have a plan for heat waves or unusual temperature swings, especially if you know you’re sensitive to these changes
- Climate awareness: As climate change brings more extreme weather, discuss adaptation strategies with your healthcare team
Questions to Ask Your Doctor
- “Do you see any seasonal patterns in my mood episodes?”
- “Should we adjust my treatment plan based on the time of year?”
- “Are there preventive strategies I can use before my ‘difficult’ season arrives?”
- “Would light therapy or other seasonal treatments help me?”
- “Should I be concerned about heat waves triggering manic episodes?”
- “How can I prepare for extreme weather events?”
- “Should temperature and weather be part of my mood tracking?”
- “How do we balance my seasonal response patterns with the suicide prevention benefits of my medications?”
- “What are the risks and benefits of each medication option for my specific situation?”
Important Safety Reminders
Never stop taking mood stabilizers without medical supervision, even if you feel they’re not working perfectly for your mood episodes. These medications may be providing life-saving protection in ways you can’t see. The goal isn’t to find a perfect medication – it’s to find the right combination that keeps you safe while managing your symptoms as well as possible.
The Bigger Picture
This research is exciting because it moves us away from a “one-size-fits-all” approach to treating bipolar disorder. Instead, it suggests that understanding your unique seasonal patterns may lead to more personalized and effective treatment.
However, it also highlights how complex bipolar treatment really is. Your doctor must consider not just how well a medication controls your mood episodes, but also:
- How does it affect your suicide risk
- Your overall safety and long-term outcomes
- Potential side effects and quality of life
- How different medications work together
The bottom line: If you’ve noticed that your bipolar symptoms seem tied to certain seasons, trust your instincts. This isn’t just a coincidence – it’s a real phenomenon that should be part of your treatment conversation. But remember, effective bipolar treatment is about finding the right balance of medications that keep you safe while managing your symptoms, not just finding the “perfect” medication for mood episodes.
What Comes Next
While this study provides valuable insights, the researchers are careful to note that they can’t yet say whether seasonal patterns cause treatment resistance or whether treatment resistance leads to seasonal patterns. Those questions will require more research.
Scientists are also working to understand the biological mechanisms behind these seasonal patterns. Why do some people’s brains respond differently to changing seasons? The answers could lead to entirely new treatment approaches.
Hope for the Future
This research represents a significant step forward in our understanding of bipolar disorder. For too long, people with bipolar disorder have struggled with treatments that don’t work well or have had to try multiple medications before finding relief.
Most importantly: If you’re currently taking mood stabilizers, continue taking them as prescribed, even if you feel they’re not working perfectly for your mood episodes. These medications may be providing crucial protection that you can’t see. Any changes to your medication should only be made with your doctor’s guidance.
Lastly, remember you’re not alone in this journey, and every new piece of research brings us closer to better treatments and brighter outcomes for everyone living with bipolar disorder. Also, know that you are always cordially welcome to call my office and get the support you need.
This article is for informational purposes only and should not replace professional medical advice. If you’re experiencing thoughts of self-harm or suicide, please get in touch with the 988 Suicide & Crisis Lifeline by calling or texting 988, or reach out to your healthcare provider immediately.
References
Clery, P., et al. (2025). Heat may worsen mania but ease depression, study finds. Journal of Affective Disorders.
Ercis, M., et al. (2025). Seasonality linked to different bipolar features, treatment response. Presented at the American Psychiatric Association 2025 Annual Meeting, May 17, 2025.
Lee, J., et al. (2025). Mood stabilizers show protective effects against suicide. Journal of Psychiatric Research. Published
