Last year, Sinan Sonmezler of Istanbul refused to keep going to school. His eighth-grade classmates called him “weird” and “stupid,” and his teachers rebuked him for his tendency to stare out the window during class. The school director told his parents he was “lazy.”

Sinan has attention-deficit hyperactivity disorder, a condition still little understood in many parts of the world.

“He no longer believes he can achieve anything, and has quit trying,” said Sinan’s father, Umit Sonmezler, a mechanical engineer.

While global diagnoses of A.D.H.D. are on the rise, public understanding of the disorder has not kept pace. Debates about the validity of the diagnosis and the drugs used to treat it — the same that have long polarized Americans — are now playing out from Northern and Eastern Europe to the Middle East and South America.

Data from various nations tell a story of rapid change. In Germany, A.D.H.D. diagnosis rates rose 381 percent from 1989 to 2001. In the United Kingdom, prescriptions for A.D.H.D. medications rose by more than 50 percent in five years to 657,000 in 2012, up from 420,000 in 2007. Consumption of A.D.H.D. medications doubled in Israel from 2005 to 2012.

The surge in use of the medications has prompted skepticism that pharmaceutical firms, chasing profits in an $11 billion international market for A.D.H.D. drugs, are driving the global increase in diagnoses. In 2007, countries outside the United States accounted for only 17 percent of the world’s use of Ritalin. By 2012, that number had grown to 34 percent.

“We need to be worried about the industry pressures, and we need to be worried about overdiagnosis, for sure,” said Luis Rohde, a professor of child psychiatry at Federal University of Rio Grande do Sul in Brazil, and president of the World Federation of A.D.H.D.

“But we also need to see the suffering of these families, and of children who are not being able to grow up healthy without the diagnosis.”

For parents of children struggling with attention problems, the most urgent issue is that their children aren’t getting the medical, social or educational support that they need.

“How can they be so cruel?” asked Olga Elizabet Abregu on the Facebook page of TDAH Argentina, an A.D.H.D. support group. Ms. Abregu is a mother in San Miguel de Tucumán, Argentina, and she was lamenting the fact that none of her son Santino’s friends had shown up for his birthday party.

Santino, 8, has been given a diagnosis of A.D.H.D. His mother said one of his teachers later told her that other parents had forbidden their children to play with him.

Ms. Abregu moved her son out of his overcrowded public school to an expensive private school — a financial sacrifice compounded by the fact that she also quit her job as a state-paid janitor because advocating for Santino with his teachers and helping him with homework and social challenges was taking so much time.

“Here where we live no one knows about A.D.H.D.,” she wrote in an email, “and the few people who’ve heard of it say they don’t believe in it, that it’s only rude kids without limits.”

Ms. Abregu began taking her son to psychologists at age 4 because of his unruly behavior, which at the time included hitting other children and not being able to share. Last April, Santiano was given his diagnosis by a neurologist who prescribed stimulant medication.

Ms. Abregu and her husband have so far hesitated to fill that prescription, because of worries about side effects. Yet they also worry about the consequences of not following the doctor’s suggestion. “We’re not sure if it’s right or not to deny him the medication,” she said.

In Tbilisi, Georgia, Nino Jakhua sought advice about medication for her 6-year-old son, Nikoloz, who had recently been given a diagnosis of A.D.H.D. But Georgia bans the stimulants that are the front-line medications used to treat the disorder elsewhere in the world.

So instead, a neuropathologist in Tbilisi prescribed therapy and supplements, including butyric acid, glycine, glutamine, magnesium, vitamin B6 drops and omega-3 capsules, none of which are conventional treatments for the disorder.

The therapy seems to have helped, his mother said, yet she wonders if medication might help him more. “He moves a lot, runs back and forth and hugs people roughly with the request to play with him,” she said. “He has a trouble sitting for more than 10 minutes for drawing.”

Nino Margvelashvili, a neuropsychologist at the Institute of Neurology and Neuropsychology in Tbilisi, who also works as a counselor in a private school, said some parents simply smuggle in medication, most often with help from friends or relatives in Ukraine.

In many other cases, neurologists prescribe other drugs, including sedatives and medications normally used for dementia or psychosis. “They make the children dumb — I really feel sorry for them,” she said.

In many parts of the world, parents of children with A.D.H.D. say they feel stigmatized, no matter how they try to cope with the disorder.

“If you medicate, you are a bad mom,” said Patricia Oedell, who lives in a village outside Villingen-Schwenningen, Germany, and has three children with A.D.H.D. diagnoses. “And if you don’t, you are also a bad mom.”

For Ms. Oedell, the start of school this year revived painful memories of having to coax her ostracized teenage daughter to keep going to class.

Her 12-year-old son, who also has been diagnosed with A.D.H.D., has meanwhile careened from crisis to crisis, such as the time he drove a nail through his finger, and the time he suffered burn injuries after carrying a lighted firecracker under his jacket.

Such problems may be familiar to American parents who have coped with the disorder, but in places like Villingen-Schwenningen, an A.D.H.D diagnosis can make parents feel like pariahs, Ms. Oedell said.

“In Germany, it’s really not accepted to be different,” Ms. Oedell said. “Either people say A.D.H.D. doesn’t exist, or they make it seem like some terrible moral problem.”

For the parents of Sinan, the Turkish eighth grader, the challenges of coping with A.D.H.D. in Istanbul were ultimately too great. They began to search for a school outside their home country to which to send him, and chose a program in Utah that offers support for students with A.D.H.D.

The school will cost the family $10,000 a month, forcing them to drain their savings and seek help from relatives, but they don’t see an alternative.

“We are so sorry that we will not see and live with him while he grows into adulthood, and to have him so far away,” his father, Umit, wrote in an email. “We then remind ourselves that this can be a lifesaving step for him and try to calm ourselves. It is hard.”