The tendency to treat childhood hyperactivity (ADHD) with drugs may have reached a plateau in the UK, following a steep rise in the number of prescriptions for these medicines over the past 20 years, according to a new study published in the online journal BMJ Open
However, children with ADHD who are prescribed drugs often continue with this course of treatment for much longer than their European or US peers, the study show.
The researchers base their findings on an analysis of Clinical Practice Research Datalink (CPRD) records, relating to children up to the age of 16 who had been prescribed at least one drug to treat ADHD between 1992 and 2013.
The CPRD is one of the world’s largest collections of long-term anonymised primary care medical records. It is broadly representative of the UK population, covering around 8% of the total.
The researchers analysed the data to estimate trends in ADHD prescribing patterns among children between 1995 and 2013, and the length of treatment for those diagnosed with the condition. During this period, 14,748 children under the age of 16 (85% of them boys) were given at least one prescription for an ADHD drug, with methylphenidate accounting for 94% of all prescriptions.
Over half (58%) of the children received their first prescription between the ages of 6 and 11; around 4% were 5 years old when they were first prescribed an ADHD drug. The use of these drugs in this age group soared by a factor of 35, from 1.5 per 10,000 children in 1995 to 50.7/10,000 in 2008, after which it seemed to level off at 51.1/10,000 children by 2013.
The rate of new prescriptions rose eight-fold over the same timeframe, reaching 10.2 per 10,000 children in 2007, but subsequently falling to 9.1/10,000 in 2013.
These patterns may reflect the impact of National Institute for Health and Care Excellence (NICE) guidelines issued in 2008, and/or concerns about the potential impact on the heart of long-term use, suggest the researchers.
UK prescribing rates for ADHD drugs are considerably lower than they are in many other countries, the researchers point out. They are 10 times lower than in the US, up to 5 times lower than in Germany, and 4 times lower than in the Netherlands, although UK rates are twice as high as in France.
Nevertheless, the course of treatment tends to be longer than in these countries, the published evidence indicates. More than three out of four UK children (around 77%) were still being prescribed ADHD drugs a year after diagnosis and 60% were still on treatment two years later, the figures show.
The probability of stopping ADHD drugs within six years seemed to be higher in 11- to 15-year-olds than it was in 6- to 10-year-olds, the data showed, which may indicate that treatment is being stopped too early among young adults, say the researchers.
This is an observational study, and the researchers point out that their analysis cannot determine the causes behind the prescribing patterns they found. Furthermore, the data relate only to the issuing of prescriptions, and not to prescriptions being dispensed or drugs actually taken.
But they conclude:
Although the prevalence and incidence of ADHD drug use in children have substantially increased during the past two decades, it seems that it may have reached a plateau recently…Our study indicates a turning point in the patterns of ADHD drug prescribing in children in the UK.