It's difficult to determine whether the results show over-diagnosis of ADHD or not, said Joel Nigg, director of the division of psychology at Oregon Health & Science University in Portland.
"Although guidelines and instrumentation for diagnosing preschool children, for example, are weaker, the condition itself is developmental and expected to exist in preschool," said Nigg, who was not involved in the study. "So, many of those young diagnoses may be valid."
Symptoms of the common disorder include inattention, hyperactivity and impulsive behaviour, which can affect a child's ability to learn.
The study was done by Susanna Visser, a researcher at the U.S. National Centre on Birth Defects and Developmental Disabilities, and published in a Sept. 3 report from the U.S. Centers for Disease Control and Prevention.
The researchers interviewed nearly 3,000 parents of children ever diagnosed with ADHD and 115 parents of children diagnosed with Tourette's syndrome. About half the children with ADHD had been diagnosed before age 7, and 31 percent had been diagnosed before age 6.
Family members play an important role
Among the children diagnosed before age 6, a parent or other family member was the first one to become concerned about the child's attention or behaviour in three of every four cases, the researchers found.
Just over half the children with ADHD received their diagnosis from a general paediatrician or family doctor. Only a quarter of the children diagnosed before age 6 had seen a psychiatrist for their diagnosis, but children were even less likely to get their diagnosis from a psychiatrist as they grew older.
"One of the most striking things is that most providers are, in fact, trying to follow the guidelines - trying to use rating scales and get information from multiple informants, like teachers, in addition to parents," Nigg said.
If doctors are using information from teachers in making a diagnosis, that suggests doctors are not making quick decisions in 15 or 30 minutes based only on a parent's description of their child's behaviour, Nigg added.
Yet over-diagnosis may still be occurring, based on the report, said Dr. Danelle Fisher, vice chair of paediatrics at Providence Saint John's Health Centre in Santa Monica, Calif.
"Over-diagnosis presents a number of problems, including being improperly labelled as ADHD if, in fact, another behavioural or psychiatric problem is the cause of the symptom," Fisher said. "This could also lead to over-medication of such children."
Both Fisher and Nigg suggested it is unwise to rush to a judgement of ADHD if a preschool child seems particularly boisterous or difficult to manage.
"Children are developing rapidly at that age, and many 4-year-olds who seem excessively hyperactive tend to stabilize during the major development shift from 4 to 6 years old," Nigg said. But he added that the situation can become too severe to wait it out sometimes.
"In cases where the child is unable to learn, unable to participate in group or preschool activities, or where a negative relationship is developing between parent and child, then a professional evaluation and intervention are likely indicated," Nigg added.
Several options may be available for parents, Fisher said.
"Firstly, parents should look into parenting classes in order to help them manage difficult or unruly behaviour," Fisher said. "Secondly, if there is a family history of ADHD or other childhood behaviour disorders, neuropsychological testing should be performed by a qualified professional, including a psychologist, psychiatrist or neurologist."
A key aspect of an ADHD diagnosis, she added, is that the symptoms occur across multiple settings, such as at home and at school.
"Parents should be wary of an ADHD diagnosis made on the observation of symptoms in only one setting," Fisher said.
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