New York, Feb 9 (IANS): Usually, children with symptoms of attention deficit hyperactivity disorders (ADHD), a common behavioural disorder in kids, like poor concentration, hyperactivity and learning difficulties, tend to improve with age.

However, the disorder does not improve in some kids and one reason may be the persistent parental criticism, reveals a new research.

"Children with ADHD whose families continued to express high levels of criticism over time failed to experience the usual decline in symptoms with age and instead maintained persistent, high levels of ADHD symptoms," said Erica Musser, assistant professor at Florida International University in US.

The researchers studied a sample of 388 children with ADHD and 127 without, as well as their families, over three years. Of the children with ADHD, 69 percent were male, 79 percent were white and 75 percent came from two-parent households. 

They measured changes in ADHD symptoms over that period and measured the parents' levels of criticism and emotional involvement.

Parents were asked to talk about their relationship with their child uninterrupted. And were then rated by experts for levels of criticism -- harsh, negative statements about the child, rather than the child's behaviour -- and emotional over-involvement -- overprotective feelings toward the child, the study, published in the Journal of Abnormal Psychology, showed. 

Only sustained parental criticism (high levels at both measurements, not just one) was associated with the continuance of ADHD symptoms in the children who had been diagnosed with ADHD, the study concluded.