CHICAGO — Ritalin and other drugs used to treat attention deficit disorder are safe for adults' hearts, even though they can increase blood pressure and heart rate, according to the largest study of these medicines in adults.

The results echo findings in a study of children with ADHD, by the same researchers, published last month.

The review of health records for more than 440,000 adults aged 25 to 64 showed those taking ADHD drugs had about the same number of heart attacks, strokes and sudden heart-related deaths as adults who didn't use those drugs.

The research will be published in the Journal of the American Medical Association's Dec. 28 print edition, but was released online Monday because of its public health importance, journal editors said.

Although attention deficit disorder is usually thought of as a condition in childhood, many continue to have symptoms as adults, including impulsive, fidgety behaviour and difficulty focusing or paying attention. ADHD affects about 4 per cent of U.S. adults, roughly 9 million. About 8 per cent of U.S. children aged 3 to 17, or 5 million kids, have ever been diagnosed with the disorder, government statistics show.

More than 1.5 million U.S. adults were taking stimulants used for ADHD in 2005, and use of ADHD drugs increased more rapidly in adults than in kids over the past decade, the study said.

More than 150,000 ADHD medication users were involved in several states. Their health records over up to 20 years were compared with similar adults who did not use those drugs.

Overall, there were 1,357 heart attacks, 575 strokes and 296 sudden cardiac deaths. Roughly equal numbers occurred in ADHD drug users and nonusers.

Study participants used the drugs for an average of less than a year, which is short, but the upper range of use was almost 14 years, and there was no sign of increasing risk with longer use, the authors said, led by Laurel Habel of the research division at Kaiser Permanente Northern California.

A journal editorial says the study provides encouraging news, given lingering concerns about isolated reports of heart problems and sudden deaths in users of some ADHD drugs.

The findings support the Food and Drug Administration's decision in 2006 against putting a black box warning about serious heart events on ADHD drug labels. But despite the results, medical histories and exams should still be performed for all patients before starting ADHD drugs, and periodic evaluations should be done during drug treatment, said editorial author Dr. Philip Shaw of the National Human Genome Research Institute.

The federal Agency for Healthcare Research and Quality and the FDA helped pay for the study.