May is consistently the month with the most suicides in the United States. According to CDC data spanning 1999 to 2010, May ranked among the top three months for suicide in every single year studied. June, July, and August also rank high, making late spring and summer the deadliest period, not winter as many people assume.
This surprises most people. The widespread belief that suicides spike during the holidays is one of the most persistent myths in public health. In reality, December ranks as the lowest or second-lowest month for suicide in all 12 years the CDC analyzed. November consistently falls in the bottom five, and February was the lowest or second-lowest in 10 out of 12 years.
Why Spring, Not Winter?
The spring suicide peak has been documented for more than a century, and researchers have several explanations for why it happens. The most studied involves how sunlight affects brain chemistry. During fall and winter, the brain produces more of the proteins that clear away serotonin, the chemical messenger tied to mood regulation. When spring arrives and daylight hours increase rapidly, those proteins drop off. This creates a temporary imbalance: serotonin levels are shifting, but they haven’t stabilized yet. That transition period, rather than the dark months themselves, appears to be when vulnerability is highest.
Think of it this way. During winter, people with depression may be in a low-energy state. As spring light exposure increases, energy and motivation can return before mood fully improves. Someone who lacked the drive to act on suicidal thoughts during the darkest months may find that drive returning while still deeply depressed. This mismatch between energy and emotional state is one of the leading theories clinicians point to.
The Pattern Holds Worldwide
This isn’t just an American phenomenon. In the Southern Hemisphere, where the seasons are reversed, the same spring peak appears, just shifted by six months. A study of suicide data from Victoria, Australia, published in the American Journal of Psychiatry, found that suicides were lowest in winter and highest during spring and summer, closely tracking daily hours of bright sunlight. The fact that the pattern follows seasons rather than calendar months strongly suggests a biological mechanism tied to light exposure, not cultural events like holidays or tax season.
Pollen as a Contributing Factor
A newer and somewhat unexpected line of research points to airborne pollen as an additional trigger during spring months. A large study combining daily pollen data from 186 counties across 34 U.S. metropolitan areas with suicide records from 2006 to 2018 found a clear dose-response relationship. As pollen levels rose through four tiers, suicide risk climbed with them: 4.5% higher at the second level, 5.5% at the third, and 7.4% at the highest.
Pollen triggers inflammation throughout the body, including the brain, and that inflammatory response can worsen mood and cognitive function. The effect was even stronger for people with known mental health conditions, who showed an 8.6% higher incidence of suicide on the highest-pollen days. Researchers estimate that pollen may have been a contributing factor in roughly 900 to 1,200 suicide deaths per year during the study period. As climate change extends and intensifies pollen seasons, that number is projected to grow.
Why the Holiday Myth Persists
Media coverage is the main reason people associate suicide with the winter holidays. News stories about loneliness and depression during Christmas and New Year’s reinforce the idea year after year, often without citing data. The Annenberg Public Policy Center has repeatedly urged journalists to stop perpetuating this myth, noting that it can actually discourage people from seeking help during the months when risk is genuinely highest.
There’s also an intuitive logic to the myth that makes it sticky. Cold, dark, isolated months feel like they should be more dangerous. But human psychology doesn’t always work that way. The contrast between improving external conditions and persistent internal suffering can be more destabilizing than the darkness itself. Spring brings social pressure to feel better, go outside, and re-engage. For someone in a severe depressive episode, watching the world brighten while their inner experience stays the same can deepen feelings of hopelessness and isolation.
Psychiatric Hospitalizations Follow the Same Pattern
It’s not just completed suicides that peak in spring. Involuntary psychiatric hospitalizations show the same seasonal curve. Data from Greece found that the highest number of emergency mental health admissions occurred around mid-June, running about 6.5% above the yearly average. The lowest point fell in mid-December, about 6% below average. This parallel pattern reinforces that the spring peak reflects a genuine increase in psychiatric crises, not just a statistical quirk in suicide data.
What the Monthly Breakdown Looks Like
To put it in perspective, the general ranking from highest to lowest suicide months in the U.S. looks roughly like this:
- Highest risk: May, July, June, August
- Moderate risk: March, April, September, October
- Lowest risk: November, February, January, December
These rankings shift slightly from year to year, but the broad pattern is remarkably stable. May and July trade the top spot most often, with the summer months consistently clustering at the top and the winter months consistently at the bottom. The gap between the peak and trough months is meaningful: it’s not a subtle statistical difference but a consistent, measurable swing that holds across more than a decade of national data.