Realizing that your brain is slowing down can be jarring. After the age of, say, 45, anyone might start forgetting names, misplacing items, or struggling to pay attention, and the onset of such symptoms can often prompt a visit to a doctor, if only to confirm a patient’s hunch that the passage of time is to blame. Yet, as ever more of the United States’ aging population enters the “What’s happening to my brain?” stage of life, many patients are asking a new question, providers told me: Am I just getting old, or do I have ADHD?In recent years, awareness of ADHD has spread dramatically—CDC estimates from 2020 to 2022 showed that roughly 11 percent of American children aged 5 to 17 had received a diagnosis. Now many Americans in midlife and beyond have started to question whether their cognitive chaos really is just a symptom of aging. For at least some people, the answer might very well be that they have undiagnosed ADHD and that the symptoms are becoming too prominent to cope with. Because the condition manifests differently as people age, the answer can also be “both.”Historically, ADHD was closely associated with overactive boys. But global studies suggest that roughly 3 percent of people older than 50—which would translate to about 3.6 million Americans—are expected to have ADHD, David Goodman, an expert on adult ADHD at Johns Hopkins University, told me. Tensions persist around whether, in general, ADHD is overdiagnosed or underdiagnosed. But as awareness continues to rise among providers and the general public, diagnoses have been climbing in populations that were previously overlooked. The CDC reports that prescriptions for stimulants increased “substantially” among people in midlife from 2020 to 2021.Midlife can complicate the already tricky process of diagnosing ADHD, though. Adult ADHD was directly addressed in the DSM-5, the American Psychiatric Association’s handbook of diagnoses, only in 2013, and it’s barely touched upon in medical schools, so many providers don’t think of it as a possible explanation for a patient’s worsening condition, Goodman said. As I have written previously, the only clinical guidelines for diagnosing or treating ADHD focus on childhood, and the disorder can show up very differently across the lifespan. For example, what looks like physical hyperactivity in childhood may manifest as internal restlessness later in life. Few physicians are trained to treat adult ADHD, and even those who are might struggle to tease apart the disorder’s symptoms from those of other health conditions that arise in midlife.[Read: Adult ADHD is the Wild West of psychology]The potential causes of declining cognition in midlife are numerous and frequently intersect. The shifts associated with “normal” aging can partly be attributed to the natural shrinkage of the brain and a decrease in the number of its neuronal connections. Mental- and cognitive-health consequences similar to those of ADHD can arise from psychiatric conditions that are prevalent in midlife, such as depression and anxiety. Mild neurocognitive disorder, a stage between healthy cognition and dementia that is common in people aged 65 and older, also has similar signs as ADHD, including missing appointments and frequently losing things. (Crucially, people with MND, but not ADHD, tend to forget words and how to spell them.) For some people, early-onset dementia or Alzheimer’s disease may be behind the symptoms. Caregiving, physical ailments, and increased work responsibility—all hallmarks of midlife—can exacerbate cognitive issues caused by any of these factors. “It can be tricky to rule all those things out,” Dara Babinski, a clinical psychologist at Penn State who studies ADHD across the female lifespan, told me.Middle-aged women are particularly difficult to diagnose with ADHD. That’s partly because girls are less frequently diagnosed with ADHD than boys are, so many adult women live their whole life with the disorder without ever suspecting it. It’s also because many middle-aged women are dealing with perimenopause, which comes with cognitive changes such as brain fog, trouble concentrating, and forgetfulness. The fluctuations in hormone levels that cause perimenopausal symptoms can also exacerbate ADHD by interfering with dopamine signaling in the brain, Brandy Callahan, a neuropsychologist at the University of Calgary who studies ADHD in older adults, told me.Increased awareness of adult ADHD, thanks in part to social media, has led many women to seek help for their symptoms, Babinski said. And stimulant prescriptions have risen especially sharply among women aged 50 to 54. Still, the combination of hazy diagnostic criteria and overlapping symptoms means that many older Americans with ADHD very likely don’t have a diagnosis. Even fewer are being treated, and so people may be having a worse experience of aging than they need to. A first-time diagnosis in midlife can profoundly improve the experience of aging. For one thing, it makes people feel validated at a time when major life changes can make it harder to cope with the effects of ADHD, which can include trouble maintaining relationships, paying bills on time, and performing at work. And a stimulant prescription can lead to improvements in attention, impulse control, and hyperactivity among people with ADHD.[Read: ADHD’s sobering life-expectancy numbers]Aside from improving life in middle age, a diagnosis has implications for future brain health. ADHD is associated with neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, and some types of dementia, but scientists aren’t yet sure why. One possibility is that people with ADHD struggle with habits that maintain a healthy brain, such as managing stress and getting adequate sleep and exercise, Craig Surman, a neuropsychiatrist and a scientific coordinator of the Adult ADHD Research Program at Massachusetts General Hospital, told me. Callahan and others have shown that ADHD brains have abnormal white matter—the communication pathway of the brain—which may make them less resilient to later disease. Researchers don’t know whether ADHD drugs actually protect against the underlying causes of more debilitating brain diseases. But if stimulants enable a person to maintain other habits that protect brain health, it’s reasonable to suspect that they might help.Yet stimulants aren’t prescribed to older adults as often as they are to younger people. Most ADHD drugs are FDA-approved only for people up to age 55 or 65 because they haven’t been tested in anyone older and, as such, aren’t typically covered by Medicare. Stimulants also raise blood pressure and heart rate, which can be especially risky in midlife and later, when health issues such as cardiovascular disease and obesity are common. For these reasons, some providers are hesitant to prescribe stimulants to older adults. (The federal government, too, in the Make America Healthy Again report, argued that the drugs are overused.) But evidence is growing that prescribing ADHD medications to older adults can be done safely. This makes a reliable diagnosis all the more important.The American Professional Society of ADHD and Related Disorders, known as APSARD, is expected to release the first clinical guidelines for adult ADHD this year. It’s an attempt to “put out some ground truth about how to treat ADHD,” Surman, who is on the guideline committee, told me. (He would not say whether APSARD will include specific guidelines for middle-aged and older adults.) Still, information is slow to disseminate, and there is pushback against the notion of adult ADHD from within and outside the medical field. Some providers feel that the risks of treating older adults with stimulants are not worth the benefit; other providers are concerned that the diagnosis over-medicalizes normal aging.Yet as the American population skews older, perhaps it is worthwhile to question what constitutes normal aging. The medical literature offers only a loose definition: Rapidly deteriorating cognition is not normal, but gradual decline with age is. At the very least, the rise in adult-ADHD diagnoses presents an opportunity to refine the latter notion. No one’s brain stays sharp forever, but some people may have more time to maintain their edge.