NEW YORK (Reuters Health) - Seven percent of US children aged 6 to 11 have been diagnosed with attention-deficit/hyperactivity disorder (ADHD), according to results of a national survey released Tuesday by the US Centers for Disease Control and Prevention (news - web sites) (CDC).

The survey also found that half of children diagnosed with ADHD are told they have a learning disability as well. This brings the total number of children diagnosed with at least one of these disorders to 2.6 million, according to the CDC.

"These results show that ADHD and learning disability are among the most common chronic conditions affecting school-aged children in the United States," Dr. Patricia N. Pastor and Cynthia Reuben write in the report, which was published online at www.cdc.gov/nchs.

These findings were obtained from national surveys conducted between 1997 and 1998, which included interviews with family members of 8,647 children between the ages of 6 and 11.

Significant differences exist in the frequency of diagnosis of ADHD and learning disability by gender and ethnicity, Pastor and Reuben report. Boys were three times as likely as girls to be diagnosed with ADHD alone, and twice as likely to have both conditions. In addition, white children were told they had ADHD twice as often as Hispanic and black children.

Children with learning disability were five times as likely as those with only ADHD to be enrolled in special education programs, and more than 23 times as likely as those without either condition.

Children with either condition used healthcare services more often than their peers, the investigators note. Kids with ADHD most frequently took prescription drugs on a regular basis, at rates of 54% among those with ADHD alone and 61% in those with both conditions. In contrast, only 6% of children with neither condition reportedly take prescription medications regularly.

Parents of kids with both disorders were more likely to say that their children had visited both mental health and general healthcare professionals, with 51% of kids with learning disability and ADHD using mental health services and reporting at least four healthcare visits within the past 12 months.

Of children with neither disorder, the investigators note, only 23% visited a doctor as often, and only 3% saw a mental health professional.

Children diagnosed with learning disability alone were more likely than others to live in a low-income or single-mother home, and children living in families with health insurance were more likely to be told they have ADHD without learning disability.