For many people, long summer days are a natural mood-booster. But the prospect of a sun-soaked weekend at the beach doesn’t put a smile on everyone’s face — and not only because of physical afflictions like sun allergies and poison ivy. Some people get seasonal affective disorder (SAD) in the summer. While more commonly thought of as a winter condition, SAD refers to any pattern of recurrent depressive symptoms that flare up in one season and retreat in others, explains Jenna Hennessey, a psychologist at Columbia University Medical Center. Going forward, some experts predict an uptick in summer SAD diagnoses due to rising temperatures and increasing allergens, two possible triggers that are both related to climate change.

There’s still a lot for researchers to learn about this condition, but if the summer blues are a recurring thing for you, here’s what we currently know about the issue and how to find help. 

More than summer blahs

About five percent of US adults have seasonal affective disorder; one-fifth of them are thought to have the summer variety (so, one percent of the total population), Hennessey says. But summer SAD hasn’t been studied extensively, nor is it well-known among the general public. So it might be more common than current estimates indicate. Even when people do realize they feel off during the summer, they might attribute their symptoms to another issue.

What we do know: The hallmark symptoms of winter SAD are an increased sleep drive and appetite (which can lead to weight gain) and decreased activity level, a behavior pattern reminiscent of hibernation in animals. Summer SAD essentially causes opposite symptoms: Difficulty sleeping (or even insomnia); reduced appetite (sometimes with weight loss); heightened feelings of agitation, restlessness and anxiety; and sometimes violent episodes, according to a 2015 study.

For these symptoms to amount to summer SAD, they need to occur almost daily for most of the day, emerge at least two years in a row, and cause significant distress and interference with daily life, Hennessey adds. And they can’t be rooted in the anniversary of a death or other major loss that took place during warmer months, says Dr. Teodor T. Postolache, a professor of psychiatry at the University of Maryland School of Medicine.

What explains these particular seasonal changes? Researchers can’t say for sure yet, but they’ve found preliminary evidence to support a few hypotheses, Postolache says.

One hypothesis is that, for people with summer SAD, heat and humidity impairs thermoregulation, the ability to control your body temperature. This could be tied to the neurotransmitter serotonin. “If someone has an abnormality in the production or absorption of serotonin, it impacts their mood and behavior, and we see that in individuals who have summer SAD,” Hennessey says. He adds that SSRIs, a class of antidepressants that increase the available supply of serotonin in the brain, “end up being really effective to treat SAD,” indicating that serotonin plays a role.

Another hypothesis is that people who experience SAD in the summer have higher sensory processing sensitivity. This means they have stronger than average reactions to environmental stimuli, such as temperature. In one study of 61 people, those with any type of SAD scored higher for this type of sensitivity than other participants. “Someone who is highly sensitive to high temperatures may be more prone to irritability and irritation,” Hennessey says.

Then there’s the theory that longer periods of daylight throw off our sleep-wake cycles by interfering with melatonin. Hennessey says. Melatonin is a hormone released by the pineal gland when it’s dark outside; it tells our circadian clock it’s time to sleep. Exposure to bright light at night can suppress its release, preventing the body from powering down on schedule. 

Lastly, allergies may play a role. In a 2019 study co-authored by Postolache, researchers found that Amish individuals with summer SAD reported worse moods on days with high pollen counts — but those with winter SAD didn’t. The thinking is that inflammation caused by seasonal allergies may trigger the changes in mood, but more research is needed.

Beat the heat and block out light

Although the root causes of summer SAD are still up in the air, psychologists do know that cognitive behavioral therapy (CBT) and antidepressants such as SSRIs can help manage symptoms. “If you notice there is a pattern to your mood and potentially agitation, anxiety and restlessness that is causing impairment in your life, seek professional help,” Hennessey says.

Behavioral changes that help restore your sleep-wake cycle may also help alleviate summer SAD.

Behavioral changes that help restore your sleep-wake cycle may also help alleviate summer SAD, she adds. That might mean using blackout curtains to keep your bedroom dark, or sleeping somewhere with air conditioning if you suspect the underlying issue is poor thermoregulation or high sensory processing sensitivity. (With winter SAD, by contrast, light therapy is often recommended to increase bright light exposure.)

If allergies are getting you down, seeing an allergist to determine your specific triggers and how to deal with them could make a difference. Keep in mind, however, that just as the root causes of SAD are still being worked out, these fixes are similarly unproven, Postolache says. But trying them is low risk since they don’t cause side effects (aside from possible minor ones from allergy medications). 

The bottom line is that you can do more than grin and bear your way through summer SAD. “There are ways to target and treat this. You don’t have to be miserable every summer,” Hennessey says.

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