Summer seasonal affective disorder hides in plain sight

When most people hear the words seasonal affective disorder, they picture winter. Dark mornings. Short days. Cold weather. Fatigue. Oversleeping. Wanting to stay under the covers. Only wanting to go out for donuts.

But seasonal depression does not always come in winter. For some people, summer is the difficult season. And summer-pattern seasonal affective disorder can look very different from the winter depression most of us recognize. Instead of slowing down, a person may feel increasingly restless. Instead of sleeping too much, they may barely sleep. Instead of eating more, their appetite may disappear. They may feel anxious, irritable, overstimulated, physically uncomfortable, and increasingly desperate for relief. Sometimes, they feel trapped by the season itself.

I recently saw this pattern unfold in a patient I had been treating for approximately seven months. Certain identifying details have been changed or omitted to protect confidentiality. He was a 41-year-old man whom I knew reasonably well clinically. I had seen him depressed before. But I had never seen him quite like this. He was on edge. Irritable. Restless. Desperate for help. He kept describing a feeling of being trapped.

As we talked, an important pattern began to emerge. He had experienced something similar during previous summers, although this year was substantially worse. Summer, for him, was not restorative. It was oppressive.

When there is no comfortable place to go

Heat had become a significant trigger for his mood. He increasingly avoided going outside during the day because being in the heat made him feel physically miserable and emotionally worse. At the same time, pollen counts were high, and he suffered from significant seasonal allergies. When he walked his dog, he wore a mask to reduce his pollen exposure. But in the summer heat, the combination of the mask, high temperature, and physical discomfort made him feel almost suffocated.

Going back inside did not solve the problem. His apartment had become uncomfortable too. He normally kept his home around 71 degrees Fahrenheit, a temperature at which he felt comfortable and could sleep. Now he had allowed the apartment to reach approximately 81 degrees Fahrenheit. Why? Because running the air conditioner seemed to worsen his allergy symptoms. He lived in a building more than 30 years old with a history of water damage. He was concerned that when the air-conditioning system ran, airborne irritants from the building or HVAC system were aggravating his congestion and swollen eyes.

He also worked 100 percent remotely. His apartment was not simply where he slept at night. It was where he spent nearly his entire day. There was no commute taking him into a different environment. No office to provide several hours of physical separation from the apartment. No routine change of scenery. No natural transition between home and work. The same environment that felt physically uncomfortable and increasingly intolerable was also his workplace.

So he faced an impossible-feeling choice. Run the air conditioner and feel congested and physically miserable. Or turn it off and become unbearably hot. Outside felt intolerable. Inside felt intolerable. And because he worked entirely from home, there was very little meaningful escape from either.

He wasn’t sleeping because of the heat. As his sleep deteriorated, so did his mood. He began searching for another apartment but struggled to find one. Then came another worry: What if other older buildings in the area had similar environmental problems?

What struck me was how many factors had converged at once:

• Heat
• Sleep deprivation
• Allergies
• Physical discomfort
• Reduced outdoor activity
• Environmental concerns
• Social and environmental isolation associated with working entirely from home
• Loss of separation between work and an increasingly distressing home environment
• Loss of control over his own living space and “no escape”
• The growing perception that there was nowhere he could go to feel comfortable

This was not simply, “I don’t like hot weather.” His environment appeared to be interacting with his biology, sleep, work structure, behavior, and mood in a self-reinforcing loop. And it raises an important clinical question: How often do we fail to recognize summer-pattern seasonal depression because we are only looking for SAD in the winter?

Yes, seasonal affective disorder can happen in summer

Seasonal affective disorder, more accurately described diagnostically as major depressive disorder or bipolar disorder with a seasonal pattern, is characterized by recurrent mood episodes associated with a particular time of year. The DSM-5-TR seasonal-pattern framework requires a recurring temporal relationship between mood episodes and a particular season, characteristic remission or substantial improvement at another time of year, and a pattern that predominates over nonseasonal episodes. A recurring seasonal pattern generally needs to be demonstrated over at least two years.

Most people with seasonal depression experience symptoms during fall and winter. A smaller group experiences the opposite pattern, with symptoms emerging or worsening during spring or summer. Summer-pattern SAD remains considerably less studied than winter SAD. That does not mean it is clinically insignificant. It may mean we are simply less likely to recognize it.

Summer depression can look very different

One reason summer-pattern SAD may be missed is that clinicians and patients are often looking for the wrong symptoms. Classic winter-pattern seasonal depression often includes:

• Oversleeping
• Low energy
• Increased appetite
• Carbohydrate cravings
• Weight gain
• Social withdrawal

Summer-pattern depression may present almost like the physiological opposite. Commonly described symptoms include:

• Insomnia
• Decreased appetite
• Weight loss
• Anxiety
• Agitation
• Restlessness
• Increased irritability

The distinction matters. A patient who is exhausted, sleeping 12 hours, overeating, and withdrawing may readily be recognized as depressed. A patient who is pacing, irritable, unable to sleep, overwhelmed by heat, increasingly anxious, and saying, “I can’t take this anymore,” may not immediately fit the picture people carry in their heads of seasonal depression. Yet that patient may be extremely unwell. Agitated depression deserves particular clinical attention because distress can be intense even when the person does not appear conventionally slowed down or withdrawn.

Heat is not just uncomfortable. It affects mental health

We also need to stop treating extreme heat as merely a physical-health issue. Large epidemiological studies increasingly show that high temperatures are associated with measurable changes in mental health. A major U.S. study published in JAMA Psychiatry analyzed nearly 3.5 million emergency-department visits among more than 2.2 million people. Higher warm-season temperatures were associated with increased emergency visits for mental health conditions, including mood disorders, anxiety and stress-related disorders, substance-related disorders, schizophrenia-spectrum disorders, and self-harm. Broader systematic-review evidence has also linked increasing ambient temperature and heat waves with adverse mental-health outcomes, including psychiatric hospital utilization and suicidal behavior.

This does not mean that hot weather directly causes depression in every person. Nor does it mean every person who becomes depressed in July has summer SAD. But temperature is increasingly recognized as one environmental variable capable of interacting with psychiatric vulnerability. For some patients, heat may be clinically meaningful rather than incidental.

Heat and suicide: an important but nuanced relationship

The relationship between temperature and suicide deserves particular attention. Research across multiple countries has repeatedly found associations between higher temperatures and increased suicide risk. One often-cited meta-analytic estimate found that each 1 degree Celsius rise in mean daily temperature was associated with approximately a 1.7 percent increase in suicide incidence, although estimates vary substantially across studies, populations, and methodologies.

This is an important public-health signal. But we need to be precise about what it means. It would be inaccurate to conclude from these studies that summer-pattern SAD has been proven to carry a higher suicide rate than winter SAD. Those are different questions. Temperature-suicide studies examine population-level relationships between heat and suicidal behavior. They do not establish that people diagnosed specifically with summer-pattern seasonal affective disorder have a higher suicide rate than those with winter-pattern SAD.

What the research does tell us is that worsening depression, severe insomnia, agitation, environmental distress, and extreme heat should not be casually dismissed. When a patient becomes dramatically worse during hot weather, clinicians should ask why.

Sleep may be one of the missing links

For my patient, one feature stood out immediately: He was not sleeping. Anyone who treats psychiatric illness knows how quickly prolonged sleep disruption can destabilize mental health. Poor sleep can worsen:

• Depression
• Anxiety
• Emotional regulation
• Irritability
• Cognitive flexibility
• Stress tolerance
• Impulse control
• The ability to solve problems

Heat makes sleep more difficult because the body normally needs to dissipate heat as part of the transition into and maintenance of sleep. When nighttime temperatures remain elevated, that process becomes more difficult.

Now imagine someone already vulnerable to depression. They cannot comfortably go outside. They cannot comfortably stay inside. They work all day in the same apartment that has become a source of physical discomfort. They have little environmental separation between work, rest, and sleep. They are sleeping poorly. They are becoming progressively more irritable and restless. Activities that normally regulate their nervous system disappear. Their world becomes smaller.

After several weeks, it may no longer feel like a weather problem. It feels like there is no escape. That perception of entrapment is clinically important.

Remote work can intensify environmental entrapment

Remote work has many benefits, but in certain circumstances it can become an underrecognized amplifier of psychiatric distress. For someone whose home is comfortable and regulating, working remotely may reduce stress. But what happens when the home itself becomes the stressor?

When a person works 100 percent remotely, there may be no automatic reason to leave the house for eight or ten hours. There is no commute. No change in temperature or physical setting. No casual interaction with coworkers. No walk through a parking lot. No transition ritual signaling that the workday has ended. The bedroom, office, living room, and place of distress may all exist within the same few hundred square feet.

For my patient, these things left him feeling “trapped.” His apartment was hot. Running the air conditioner seemed to worsen his allergy symptoms. Opening himself to the outdoors meant heat and pollen exposure. And his job kept him physically anchored to the very environment from which he increasingly wanted relief. Remote work did not cause his depression. But it appeared to remove an important source of environmental variation and escape.

This is worth asking about clinically. When a patient works from home and reports worsening depression, anxiety, insomnia, or agitation, we should not only ask what they do for work. We should ask:

• Where are you physically spending your day?
• How often do you leave your home?
• Do you have another place where you feel comfortable?
• Does your work environment also function as your sleep and recovery environment?
• Do you ever get a meaningful change of scenery?

Sometimes the problem is not simply social isolation. It is environmental saturation. There is nowhere else for the nervous system to go.

Allergies, air quality, mold, and the built environment

Another lesson from this case is that psychiatric symptoms do not occur in isolation from the physical environment. Pollen, wildfire smoke, humidity, poor indoor air quality, aging HVAC systems, water-damaged buildings, housing insecurity, and the inability to afford adequate cooling all may influence how someone experiences summer.

We need to be cautious about claiming that mold, pollen, or air-conditioning systems cause seasonal depression; the evidence is not nearly that simple. But these exposures can create real physical symptoms: congestion, headaches, eye irritation, fatigue, poor sleep, difficulty breathing comfortably, and inflammatory symptoms.

Physical discomfort itself becomes a stressor. Then behavior changes. The patient stays indoors. Exercise decreases. Social contact decreases. Sleep worsens. The patient becomes hyperfocused on environmental symptoms. Their sense of safety in their own home may deteriorate. What begins as an environmental problem can become a biopsychosocial feedback loop. That is exactly why psychiatric care sometimes requires looking beyond a medication list.

Summer SAD may not be simply “reverse winter SAD”

We understand winter-pattern seasonal depression better than summer-pattern depression. Winter SAD has been extensively studied in relation to shortened photoperiod, circadian timing, melatonin, serotonin, and light exposure. Summer-pattern SAD is much less understood. Heat, longer daylight exposure, circadian disruption, humidity, sleep disturbance, and individual biological sensitivity have all been proposed as contributors.

But we should resist pretending the science is more settled than it is. Summer SAD remains understudied. Its mechanisms are likely heterogeneous. Some people may be particularly sensitive to heat. Others may be affected primarily through insomnia. Others may experience sensory overload, allergies, changes in routine, social isolation, body-image pressures, disrupted schedules, or combinations of these factors. There may not be one “summer depression mechanism.” That makes individualized assessment especially important.

Treatment cannot simply be copied from winter SAD

This is another area where clinical nuance matters. Bright-light therapy is one of the best-established treatments for winter-pattern seasonal depression. That does not mean we should automatically prescribe more bright light to someone whose symptoms consistently worsen during long, hot, bright summer days.

Evidence for specific treatments in summer SAD is remarkably limited. Antidepressant medication and psychotherapy may be appropriate when a patient meets criteria for major depression, but most treatment evidence for SAD comes from winter-pattern populations or from depression research more generally.

Environmental intervention may also be clinically important. For some patients that might mean:

• Creating a reliably cool sleeping environment
• Addressing insomnia aggressively rather than treating it as a secondary complaint
• Using blackout curtains when prolonged evening light interferes with sleep
• Moving exercise to early morning or evening
• Maintaining social contact despite avoiding midday heat
• Creating reasons to leave the home when working remotely, such as using a library, coworking space, coffee shop, or other tolerable environment when feasible
• Separating the work area from the sleep and recovery area as much as possible
• Evaluating and treating significant allergies or respiratory symptoms
• Assessing indoor-air concerns appropriately rather than either dismissing them or assuming every symptom is caused by environmental toxins

And, importantly, planning before summer arrives. If someone has become severely depressed every June, July, and August for several consecutive years, waiting until they are in crisis in July is not an adequate treatment strategy. Seasonality should become part of the prevention plan.

Clinicians should ask questions

We routinely ask depressed patients how their sleep is, how their appetite is, whether they have any suicidal thoughts, and what medications they are taking. We should also sometimes ask, “Is there a time of year when you reliably get worse?” And then go further:

• What happens during that season?
• Does heat affect you?
• Does your sleep change?
• Do you stop going outside?
• Do allergies or air quality limit your activity?
• Do you work from home, and if so, how much of the day do you spend in the same environment?
• Do you have somewhere else you can comfortably go?
• Do you become more irritable or restless?
• Does your home stay cool enough for you to sleep?
• Do you feel better once the weather changes?

Those questions may reveal a pattern that a PHQ-9 alone never will.

Psychiatric medications add another layer

Heat also deserves attention because some psychiatric medications can affect the body’s response to high temperatures. Certain antipsychotics and medications with anticholinergic properties can impair sweating or thermoregulation. Sedating medications may reduce awareness of developing heat illness. Lithium requires particular caution because dehydration and changes in sodium and fluid balance can increase lithium concentrations and toxicity risk.

This does not mean psychiatric medications should automatically be reduced or stopped during hot weather. Abrupt medication changes can themselves be dangerous. It means clinicians should identify vulnerable patients ahead of heat waves and provide individualized guidance regarding hydration, heat exposure, warning signs, and when medical evaluation or medication monitoring is necessary.

The larger issue: Climate belongs in the mental-health conversation

As extreme heat becomes more frequent, psychiatry will increasingly have to think about the environment as part of clinical care. Not ideologically. Clinically. A psychiatric history may eventually need to include questions we historically considered peripheral:

• Does the patient have reliable air conditioning?
• Can they afford to run it?
• Does their housing retain excessive heat?
• Does running the HVAC system worsen respiratory or allergy symptoms?
• Do they work entirely from home?
• How many hours per day do they spend in the same physical environment?
• Do they have somewhere else they can go?
• Do they live alone?
• Do they have access to transportation?
• Are they taking medications that increase vulnerability to dehydration or heat illness?
• Does heat reliably worsen their insomnia, agitation, substance use, psychosis, or mood?

These are psychiatric questions because the answers may influence psychiatric outcomes.

Summer is not a happy season for everyone

There is a cultural expectation that summer is supposed to feel good. Vacations. Sunshine. Long evenings. Pools. Barbecues. Everyone seems to be outside having fun. That expectation can make summer depression particularly isolating. A person may look out the window at a bright blue sky and wonder: Why do I feel worse when everyone else seems happier? Sometimes there is guilt attached to that. There shouldn’t be.

Human nervous systems do not respond identically to environmental conditions. For some people, darkness and cold are destabilizing. For others, it may be heat, excessive daylight, disrupted sleep, environmental allergens, sensory overload, environmental confinement, or the loss of routines that normally keep them regulated. The season that energizes one person may dysregulate another. The clinical task is not to tell patients which season they are supposed to enjoy. It is to recognize patterns.

What my patient reminded me

My patient did not walk into my office saying, “I think I have summer seasonal affective disorder.” He said, in essence, “I cannot get comfortable anywhere.” Outside was too hot and filled with pollen. Inside was too hot unless he ran an air conditioner that seemed to worsen his physical symptoms. And because he worked 100 percent remotely, the apartment was not merely somewhere he returned to at the end of the day. It was his entire daily environment. His home. His workplace. His sleeping environment. The place where he was supposed to recover.

He could not sleep. He could not find another apartment. He was increasingly irritable, restless, depressed, and desperate. He felt trapped. Because sometimes depression is not experienced primarily as sadness. Sometimes it feels like being trapped inside your body, your home, your environment, your workday, and a season that seems as though it will never end.

When a patient’s psychiatric state changes dramatically, we should also ask what changed around them: the temperature, the light, the air, their sleep, their environment, their work setting, their routine, their ability to leave the house, and their sense of control. Mental health does not exist separately from the body or the environment in which that body has to live. And sometimes the season everyone else is celebrating is the very season our patient is trying to survive.

A note on safety

Seasonal depression is still depression. Anyone experiencing severe hopelessness, escalating agitation, inability to sleep for prolonged periods, thoughts of suicide, or a feeling that they may not be able to keep themselves safe should seek urgent professional help. In the United States, call or text 988 for the Suicide & Crisis Lifeline. In an immediate emergency, call 911 or go to the nearest emergency department.

Carrie Friedman is a dual board-certified psychiatric and family nurse practitioner and the founder of Brain Garden Psychiatry in California. She integrates evidence-based psychopharmacology with functional and integrative psychiatry, emphasizing root-cause approaches that connect neuro-nutrition and gut–brain science, metabolic psychiatry, immunology, endocrinology, and mind–body lifestyle medicine. Carrie’s clinical focus bridges conventional psychiatry with holistic strategies to support mental health through nutrition, physiology, and sustainable lifestyle interventions. Her professional writing explores topics such as functional medicine, autism, provider well-being, and medical ethics.