Over her life, Tanya Murphy had become accustomed to hiding her depression. In the Christian social circles in Georgia where she raised her three children, this was the rule — not the exception, she said.

“God forbid you have a mental health issue,” said Ms. Murphy, 56, who now lives in Arlington, Va. “And if you do? Girl, all you got to do is fast and pray.”

But by the time she reached her late 40s, she knew she couldn’t mask her problems any longer.

Ms. Murphy had developed anxiety and started having thoughts of ending her life. She knew she was smart but she didn’t feel that way. Her difficulty focusing — as a child, her teachers called her a daydreamer — had translated into spending thousands of dollars on entrepreneurial projects that she later lost interest in and abandoned.

After researching her symptoms online, Ms. Murphy realized that she might have attention deficit hyperactivity disorder, or A.D.H.D., a neurodevelopmental disorder that typically involves inattention, disorganization, hyperactivity and impulsivity. She was finally diagnosed, at age 53, by a psychiatric nurse practitioner. After she began taking the non-stimulant A.D.H.D. medication Strattera, attending regular therapy sessions and meditating, her ability to focus improved and the anxiety and the depression faded away.

“I cried with joy,” she said. “I knew that I wasn’t crazy. I knew that I wasn’t broken. I wasn’t a failure. I wasn’t lazy like I had been told for most of my life. I wasn’t stupid.”

Over the last 20 years, clinicians have increasingly recognized that A.D.H.D. symptoms, which begin in childhood, can linger into adulthood, and that some groups — like women and people of color — are more likely to be underdiagnosed early in life. Now, with the rise of telemedicine, increased awareness of A.D.H.D. and changing attitudes about mental health treatment, new A.D.H.D. diagnoses are surging among older Americans.

An analysis by Truveta, a health care data and analytics company, shows that the rate of first-time A.D.H.D. diagnoses has been on the rise since 2021, but the increase has occurred only among people 30 and older. From January 2021 to October 2024, the rate of first-time diagnoses rose about 61 percent among those ages 30 to 44 and 64 percent among those ages 45 to 64.

As a result, about 31 percent of first-time diagnoses are now among people ages 30 to 44, the largest proportion of any age group. (In 2018, younger adults took the top spot.)

The analysis, which was done at the request of The New York Times, drew on Truveta’s database of 30 health systems, which included more than one million people who had received first-time A.D.H.D. diagnoses.

A survey conduced in August by the Ohio State University Wexner Medical Center found that 25 percent of adults believed they had undiagnosed A.D.H.D. But among U.S. adults, the disorder is thought to occur in only 6 percent of the population. Experts believe that the array of social media videos about the disorder is partly to blame for the increase in self-diagnosis. On TikTok alone, there are 3.7 million posts with the hashtag #ADHD.

“All these people who have been walking around, never diagnosed before, are now saying, ‘Wow, these symptoms resonate with me,’” said Dr. David W. Goodman, an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine.

This is especially true of women. Data from the Centers for Disease Control and Prevention shows that 61 percent of women with A.D.H.D. are diagnosed with the disorder in adulthood compared with 40 percent of men. Research also suggests that A.D.H.D. symptoms can worsen or even appear for the first time around menopause.

Outside stressors, such as the pandemic, may have added gasoline to the fire for people with “long-simmering difficulties,” said Russell Ramsay, a psychologist who treats adult A.D.H.D.

In 2020, Kyle Lampe, 37, who lives in Norfolk, Mass., had to pivot from event production to a job in health care. Then, in 2022, he and his wife had their first child and bought a house, after having put both off during the pandemic. The following year he was promoted at work.

With his busier schedule, he lost the periods of respite that he had relied upon to have enough energy to focus on the tasks ahead of him and organize his day.

Mr. Lampe began watching videos about A.D.H.D. on social media and related to concepts like the “wall of awful,” or a seemingly insurmountable task that needs to get done. He recognized A.D.H.D. symptoms in his younger self, too.

“I’m a big fidgeter,” he said. “Even back in school I would drum on desks and the teacher would be like, ‘Kyle, please stop.’”

His report cards from elementary school were peppered with comments about how he would interrupt during class and have difficulty staying still or being organized.

After he was finally diagnosed in August, he wondered if he might have maintained more of his friendships, or whether his career might have taken a different path, had he known about his A.D.H.D. all along.

Both Mr. Lampe and Ms. Murray opted to undergo in-person neuropsychological testing — Ms. Murray paid $2,500 out of pocket while Mr. Lampe’s testing was largely covered by insurance. But others go online — to companies like ADHD Online, Amwell or Lifestance. And still others are diagnosed by a general practitioner or a psychiatrist. The lack of U.S. clinical guidelines for diagnosing A.D.H.D. in adults means that there isn’t a consistent way that everyone goes about it.

Much of the surge in new diagnoses is “legit,” said Stephen P. Hinshaw, a professor of psychology and an expert in A.D.H.D. at the University of California, Berkeley. But, he added, the pull of social media and the “still-too-easy diagnoses” available online “with a few self-report questions and no corroboration” are an unfortunate flip side.

In the case of Dolores Brown, 46, who lives in Milwaukee, it was a new therapist who floated the possibility of A.D.H.D. Her counselor believed that Ms. Brown’s earlier diagnosis of bipolar disorder, made by another provider years ago, was incorrect.

When she was diagnosed with A.D.H.D. in 2023, Ms. Brown felt relieved. Up until that point, she added, she had become convinced that she was “just crazy” and that nobody knew how to help.

As a child, she said, she had been identified as academically gifted — and while she always had a lot of ideas, she struggled to focus and complete tasks. In college, she fell asleep in class if she wasn’t engaged. She flunked three courses and, in other cases, barely scraped by with a C or a D. Doing a load of laundry felt impossible, so when she ran out of clean clothes she would go out and buy more.

At the time, nobody — including herself — stopped to think that maybe something was different about her brain. “I’m not doing what I’m supposed to do,” she would tell herself. “I’m a failure.”

This summer she began taking the stimulant medication Vyvanse for her symptoms and was finally able to focus on the things that had eluded her in the past. She is now thriving in a new job that requires autonomy and organization.

Maybe, she realized, she wasn’t a “screw-up” after all.

“I was really hard on myself for so long,” she said. “Now I forgive myself.”