When you hear the term “seasonal affective disorder,” your mind likely conjures up images of days that are cold, dark and short — for good reason. Seasonal affective disorder (SAD) is a subtype of depression that strikes during a specific time of year, typically when the seasons change and most commonly at the onset of winter.

“People are really affected by the decrease in sunlight — you’ve got symptoms like hypersomnia (sleeping too much), eating too much and less interest in activities,” says Terri Bacow, PhD, a cognitive-behavioral psychologist in New York City.

But for a smaller number of people, the symptoms of SAD come with the backdrop of sunshine, pool parties and melting ice cream cones. And while summertime sadness isn’t  as common, it’s also not just a catchy Lana Del Rey song — especially for those who suffer from it.

What Does Summer Depression Look Like, Really?

According to Mayo Clinic, it can be tough for a medical doctor or mental health professional to diagnose any form of SAD because the symptoms resemble those of other mental health conditions. Still, it's clear that millions of people — about 5 percent of the U.S. population, per Mental Health America — are impacted by the condition each year. And the majority of sufferers are women.

Bacow estimates that the majority of cases are winter SAD, whereas only about 1 to 2 percent are summer or “reverse” SAD. It is also possible that the latter is underdiagnosed.

When it comes to how the two seasonal forms of SAD present, there are differences. “Winter symptoms consist of oversleeping, overeating and a dull mood,” says Sanam Hafeez, PsyD, a New York City-based neuropsychologist. “In summer, the symptoms are more likely to include insomnia, reduction in appetite, irritability and anxiety.”

RELATED: Outsmart Your Smartphone: 4 Ways to Curb Digital Distraction

Adds Hafeez: “In summer, an overabundance of sunlight reduces the production of melatonin, the hormone that controls your sleep-wake cycle. With longer days, your body has fewer hours to produce melatonin to help you sleep… too much sunlight will turn down melatonin production.”

Beyond that, hot temperatures can take a toll on you mentally and physically. “Heat can be oppressive, making the body feel uncomfortable and unsettled,” says Bacow.

It can also make some people feel “claustrophobic,” adds Hafeez. “They may spend the warmer months hiding out in their air conditioned homes, avoiding social settings, cookouts, going to the beach and outdoor exercise because of it.” The big drawback to that? “Avoiding the sun can affect your vitamin D levels, which can lead to fatigue and worsening depressive symptoms,” cautions Hafeez.

Spending more time indoors can also have a negative impact on serotonin, a chemical that plays a role in regulating mood, emotion and even appetite, since sunlight can increase serotonin levels.

What Else Can Cause Summer Depression?

But it’s not just biology at work here. There are also psychological elements that can contribute to summer depression.

Think about it: We have this notion that the season has to be fun all the time. On social media, it can look like everyone is having a better time than you, whether they’re drinking margaritas poolside or taking fabulous vacations abroad. And even if you know that your feed is just a highlight reel, scrolling through smiley summer posts can be enough to put you in a slump, especially if you’re not out there doing such ‘grammable activities.

On social media, it can look like everyone is having a better time than you... even if you know that your social feed is just a highlight reel, scrolling through smiley summer posts can be enough to put you in a slump.

“There’s internal and external pressure to optimize the season…so instead of making people feel healthier, it can make them feel more anxious," says Bacow.

Also to blame is the “rosé all day” summer culture. If you’re drinking more than usual, you may end up dehydrated, experiencing sleep disruptions (it’s a fallacy that booze helps you sleep) and dealing with the fallout of poor decisions made while buzzed or wasted. “Too much drinking is not optimal for good mental health — a little may be fine, but all day is not great,” says Bacow.

Another potential contributor: summer days tend to be less structured, especially when you weekend getaways and travel enter the mix. While those changes can be positive, they can also impact a person mentally. “We function best when we have structure: a routine, expectations and parameters for how our day is going to go,” explains Bacow.

Could You Have Summer Depression?

According to experts, few risk factors may affect a person’s odds of developing SAD in the summertime. “Research shows that SAD is highly genetic; folks with summer SAD [often] have a family history of depression or some sort of mood disorder,” notes Bacow.

Even if it doesn’t show up in your family history, you can still be at a greater risk of reverse SAD if you’ve suffered from a mental health condition, particularly depression, in the past. That’s because you may already have less serotonin in your body.

Remember the Signs

Loss of appetite, insomnia, anxiety and weight loss all point to reverse SAD. If you experience these symptoms — or simply feel “off” in the summer months — seeking help may be your first step to alleviating these effects and your overall emotional state.

“If you are experiencing ongoing symptoms of depression, anxiety and gloominess, you must seek help,” adds Hafeez. “Speak with your internist or a licensed mental health professional.”

Steps You Can Take at Home

“Creating a steady sleep routine is essential,” says Hafeez. “You can settle into your bed in a darkened setting, meditate, practice yoga, and go to bed and wake around the same time daily.”

You might also want to take a break from social media and all the comparison (even if subconscious!) that often comes with it.

“Exercising and maintaining a healthy diet are [also] essential,” says Hafeez. And the latter is especially key for those whose appetite might be affected by SAD. “People experiencing reduced appetite should do their best to ensure that what they eat and drink is providing maximum nutrition,” she explains.

For more information, read: How to Cope with Seasonal Depression.