BRITISH scientists have found the first direct evidence that attention-deficit/hyperactivity disorder (ADHD) is a genetic disorder, and say their research could eventually lead to better treatments for the condition.

Researchers who scanned the gene maps of more than 1,400 children found that those with ADHD were more likely to have small chunks of their DNA duplicated or missing.

Anita Thapar, a professor of child and adolescent psychiatry at Cardiff University who led the study, said the research should help dispel the myths that ADHD is caused by bad parenting or poor diets too high in sugar.

"This is really exciting because it gives us the first direct genetic link to ADHD. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children," she said.

ADHD is one of the most common child mentaldisorders, estimated to affect 3 to 5 percent of children globally. It is seen far more often in boys.

Children with ADHD are excessively restless, impulsive and easily distracted, and often experience difficulties at home and in school. There is no cure, but the symptoms can be kept in check by a combination of medication and behavioral therapy.

Millions of people take ADHD drugs, and global sales were around US$4 billion in 2009, according to pharmaceutical analysts at Deutsche Bank in London.

Thapar said the findings, published in The Lancet medicaljournal, would help unravel ADHD's biological basis, "and that's going to be really important in the future to develop new and much more effective treatments."

The study also showed an overlap between the deleted or duplicated DNA segments, known as copy number variants, and genetic variants linked to the brain disorders autism and schizophrenia.

This provided what the scientists said was "strong evidence" that ADHD is a neurodevelopmental condition.

• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• missing [´misiŋ] a.缺掉的；失踪的 (初中英语单词)
• mental [´mentl] a.精神的；心理的 (初中英语单词)
• affect [ə´fekt] vt.影响；感动；假装 (初中英语单词)
• restless [´restləs] a.没有休息的 (初中英语单词)
• combination [,kɔmbi´neiʃən] n.结合；联合；团体 (初中英语单词)
• medical [´medikəl] a.医学的；医疗的 (初中英语单词)
• journal [´dʒə:nəl] n.日记；日报；杂志 (初中英语单词)
• effective [i´fektiv] a.有效的；有力的 (初中英语单词)
• disorder [dis´ɔ:də] n.杂乱 vt.扰乱 (高中英语单词)
• differently [´difrentli] ad.不同地，有差别地 (高中英语单词)
• billion [´biljən] num.万亿 (高中英语单词)
• eventually [i´ventʃuəli] ad.最后，终于 (英语四级单词)
• dispel [di´spel] vt.驱逐；驱散(乌云) (英语六级单词)
• impulsive [im´pʌlsiv] a.易冲动的 (英语六级单词)
• biological [,baiə´lɔdʒikəl] a.生物学(上)的 (英语六级单词)