Phoenix recorded 113 days above 100 degrees in 2023. The summer of 2024 broke records again. By July, the average daily high in the metro area sat above 105 degrees for weeks at a stretch.
For most people, that means discomfort. For people managing ADHD, treatment-resistant depression with Spravato, or opioid use disorder on Suboxone, that kind of heat is a clinical variable. It changes how the brain functions. It changes how medications behave in the body. And it changes whether a person shows up to their next appointment.
None of this gets discussed enough in outpatient psychiatric settings, especially in the Sonoran Desert, where summer is not a season you can avoid. It lasts five months. It is the background condition of daily life. And for patients on psychiatric medications or in active treatment for a substance use disorder, those five months carry real clinical risk that deserves to be named.
This article is for patients, families, and the clinicians who work with them across the Phoenix metro area.
Why Heat Affects the Brain in the First Place
The brain runs on a narrow temperature range. When the body gets too hot, blood flow shifts toward the skin to help with cooling. That means less blood to the prefrontal cortex, the part of the brain that handles focus, decision-making, impulse control, and planning.
A 2024 study published in Ecotoxicology and Environmental Safety found that extreme high temperatures were linked to reduced cognitive performance at hourly, daily, and annual levels. An earlier study using fMRI showed that when brain temperature rises from heat exposure, executive function and motor control take a measurable hit. These are not minor or theoretical effects. They show up on tests, in behavior, and in how people manage their daily lives.
A landmark 2022 study in JAMA Psychiatry analyzed nearly 3.5 million emergency department visits across the United States from 2010 to 2019 and found that higher warm-season temperatures were directly associated with increased risk of mental health-related ER visits, with substance use disorders, mood disorders, and anxiety all showing elevated risk during hot days.
What This Means for ADHD
ADHD is a disorder of the prefrontal cortex. Attention, impulse control, working memory, and emotional regulation all trace back to the same brain circuits that heat exposure disrupts most directly. If you are already working with a brain that struggles to filter distractions and stay on task, adding extreme heat to the equation is not neutral.
A 2024 study of nearly 180,000 children found that increased heat exposure was significantly linked to worsening ADHD symptoms. Researchers noted that neuroinflammation and oxidative stress from heat exposure may be key mechanisms, and that the ADHD brain appears to be especially sensitive to these effects compared to neurotypical brains.
For adults with ADHD in Phoenix, the practical impact shows up in predictable ways during summer. Routines break down. Sleep gets worse because high nighttime temperatures in the Valley rarely drop below 90 degrees in July, and sleep is one of the primary recovery systems the ADHD brain depends on. Hydration drops, which affects dopamine signaling. Outdoor activity, which for many ADHD patients is a major regulation strategy, becomes dangerous during the middle of the day.
The medications used to treat ADHD add another layer of risk. A December 2024 paper published in Frontiers in Psychiatry examined a large real-world database and found that stimulant medications can affect how the body handles heat by altering thermoregulatory responses and increasing metabolic heat production. Stimulants raise the body’s internal temperature slightly, which matters a great deal when you are already outside in 108-degree weather. The same paper noted that this is an underexplored area, with more research needed to understand the full scope of the clinical risk.
What this means for patients: if your ADHD symptoms seem to get dramatically worse in summer, that is not a sign your medication has stopped working or that your diagnosis was wrong. It is likely a genuine neurological response to your environment. The heat is not a backdrop. It is a variable. Tell your prescriber.
What this means for prescribers: summer is a reasonable time to check in on stimulant dosing, review hydration and sleep hygiene, and adjust expectations for behavioral performance. Patients who struggle to hold structure in July are not failing. They are managing a difficult neurological environment.
What This Means for Spravato Treatment
Spravato, the brand name for intranasal esketamine, is an FDA-approved treatment for treatment-resistant depression and major depressive disorder with active suicidal ideation. It works through the NMDA glutamate receptor system, which is different from how traditional antidepressants work. Most patients receive treatment twice a week for the first month, then once a week, then once every one or two weeks as maintenance.
Spravato does not get talked about in the context of heat much, and there is no published research we could find that looks specifically at heat as a modifier of esketamine response. But there are several things clinicians practicing in Phoenix should think about.
First, the treatment setting matters. Patients must be monitored in a certified healthcare facility for two hours after each dose because of the risk of dissociation, sedation, and blood pressure changes. In Phoenix, getting to and from that appointment in July, whether on foot, in an uncooled car, or relying on public transit, can be a real barrier. Showing up already heat-stressed, dehydrated, or having skipped meals because the heat suppressed appetite changes the starting conditions for the session.
Second, the medications patients take alongside Spravato matter. A 2024 systematic review in eClinicalMedicine found that psychotropic medications, including antidepressants, can interfere with the body’s ability to regulate temperature during heat stress, even when the direct mechanism is not always clear. Patients on multiple psychiatric medications in Arizona’s summer heat are managing a combined physiological load that deserves attention.
Third, the mental health burden of summer itself is a confounding factor. Depression often worsens with social isolation, disrupted sleep, loss of routine, and reduced physical activity. All four of these happen in Phoenix in July. People stop going outside. Social plans get cancelled because it is simply too hot. This means some patients who are not responding as expected to Spravato in July may be fighting the effects of the treatment from multiple directions at once.
The clinical message for Spravato patients is concrete: hydrate before your appointment, eat beforehand, and get to the clinic in a way that minimizes heat exposure. If you notice your response to treatment seems weaker in summer, that is worth a conversation with your provider. It may reflect environmental factors rather than treatment failure.
For practices running Spravato programs in Arizona: summer appointment adherence is a real issue. Building in proactive outreach, flexible scheduling, and simple summer prep reminders into patient communication can make the difference between treatment continuation and dropout.
What This Means for Suboxone Adherence
Buprenorphine, sold under the brand name Suboxone when combined with naloxone, is one of the most effective treatments for opioid use disorder. People who stay on it have dramatically lower rates of overdose, relapse, and death. People who drop off it face immediate, serious risk.
Non-adherence and early dropout from buprenorphine treatment are persistent problems. A 2025 study published in PubMed found that almost half of Medicaid patients with opioid use disorder showed varying degrees of non-adherence to buprenorphine within the first six months of treatment, and that non-adherence was directly tied to worse clinical outcomes and higher costs.
Heat adds specific pressure points to adherence that are worth understanding directly.
Transportation is one of the biggest. Suboxone patients in outpatient programs need to come in regularly, especially in the early weeks of treatment. Phoenix’s summer makes that hard for people who do not have reliable access to a car with air conditioning. Bus stops in July are genuinely dangerous. A patient who misses an appointment because of heat exhaustion is not a patient who lacks commitment to their recovery. They are a patient who ran into a real environmental barrier.
Stability and routine are also affected. The research on buprenorphine adherence consistently shows that life disruption, housing instability, and loss of structure predict dropout. Summer in Phoenix is destabilizing for many people. People with OUD are overrepresented among unhoused populations, and being unhoused during Phoenix’s summer is a health emergency in itself. Maricopa County documented 732 deaths in 2022 among people experiencing homelessness from conditions worsened by overdose, infectious disease, and chronic conditions, often in the heat.
Physiologically, extreme heat and dehydration affect how the body processes medications. Buprenorphine is primarily metabolized by the liver. While there is no direct research linking ambient summer heat to clinically significant changes in buprenorphine blood levels in otherwise healthy outpatients, the combination of dehydration, reduced appetite, and altered sleep affects overall treatment stability and the subjective experience of cravings and withdrawal discomfort in ways that deserve attention. Craving intensity is also affected by the environment. A 2023 study published in Environmental International found that higher ambient temperatures were associated with increased emergency department visits for opioid use in California, pointing to heat as a genuine driver of relapse risk rather than just a background condition
The practical implications for Suboxone patients are real. Take your medication at the same time every day, keep it stored properly (away from direct heat and sunlight, as buprenorphine should be stored at room temperature, not in a hot car), and be honest with your provider if summer is making appointments harder to keep. There are options, including telehealth check-ins and flexible scheduling, that can keep treatment on track.
For prescribers: summer dropout is predictable. It is worth having the conversation proactively in May or June, before the heat arrives. Ask about transportation, housing stability, and what support systems look like. An early plan is easier to execute than a crisis intervention in August.
The Bigger Picture
Mental illness and extreme heat form a two-way street. Heat makes psychiatric and addiction conditions harder to manage. And people managing those conditions are often more vulnerable to heat than the general population, because of their medications, their living situations, their access to cooling, and the social isolation that often accompanies untreated or undertreated illness
If you are a patient managing ADHD, treatment-resistant depression, or opioid use disorder in the Phoenix area, summer is not the time to coast. It is the time to be more intentional about hydration, sleep, routine, and communication with your treatment team. The heat is real. Its effects on your brain and your medication are real. And the support to manage through it is available.