Attention Deficit Hyperactivity Disorder (ADHD) is a disorder affecting at least 2-4% of adults worldwide and 1 in 20 children (see e.g. Asherson, 2005; Tatlow-Golden et al., 2016; Lara et al., 2009). It is usually lifelong and causes substantial impairment, including decreased quality of life, psychosocial issues, addictive and risk-taking behaviours and premature mortality (Asherson et al., 2012; Brod et al., 2012; Lara et al., 2009; Brugha, T. et al., 2016). Symptoms must be disabling (cause pervasive impairment) for diagnosis, and can include issues with attention regulation, inattention, hyperactivity, impulsivity, emotional lability and difficulty sleeping (National Institute for Health and Care Excellence [NICE], 2018). ADHD is thought to be under-diagnosed in the UK, particularly in females (ibid.).
A recent study by MaryJo MacAvin, Mary Teeling and Professor Kathleen E Bennett addresses a gap in the knowledge of prescription patterns of ADHD medication in Ireland between 2005 and 2015 (MacAvin et al, 2020). It also examines whether prescribing of other psychotropic medication, alongside ADHD medications to young people, has changed from 2005 to 2015.
In Ireland, there isn’t universal free health care. However, the General Medical Services (GMS) scheme provides assistance with healthcare and prescription costs to people in lower income brackets. This study used data acquired from the GMS scheme, which records the specific prescriptions issued to individuals, along with their age and sex.
The study only included data from people aged 0-24 years old on the GMS pharmacy claims database, representing 35.4% of the total population of people under 24 in Ireland. The paper focussed on prescription of authorised ADHD medications: methylphenidate, atomoxetine, dexamphetamine and lisdexamphetamine. Where these were prescribed, it also focussed on whether any other psychotropic medications were prescribed in the same month, such as antipsychotics, anxiolytics, hypnosedatives and antidepressants.
The researchers looked at how the number and types of prescriptions from each December between 2005-2015 changed between different age groups (0-4 years, 5-11 years, 12-15 years, 16-24 years) and sexes (male vs female).
The number of children and young adults taking ADHD medication on the GMS scheme increased from 1,913 in 2005 to 4,853 in 2015. Prescribing was considerably higher for males, who comprise 78.3% of those receiving prescriptions, and the study found significant increases in the prescribing of ADHD medication to teenagers and early adults (aged 12-15 or 16-24) in 2015 compared to 2005. However, there have been no significant changes in the prescribing of ADHD medication to children under the age of 12 between 2005 and 2015.
Over the course of the study, methylphenidate continued to be the most prescribed ADHD medication and usage has increased in line with increased diagnosis. However, rates of prescribing non-stimulants have also increased, with atomoxetine becoming the second most frequently prescribed medication. The proportion of prescriptions for methylphenidate fell from 98% to 80% between the years 2005 and 2015.
There has been little to no change in concomitant prescribing of other psychotropic medications to those younger than 16 years old. However, in adolescents and young adults specifically, prescribing of antidepressants alongside ADHD medication has increased from 4.7% in 2005 to 15.1% in 2015. Concomitant prescribing of antipsychotics to those aged 15-24 has increased from 5.8% in 2005 to 13.7% in 2015. Concomitant prescribing of hypnotics (sleeping tablets) to all ages up to 24 has increased from 0.6% in 2005 to 2.1% in 2015. There has been a reduction in the concomitant prescribing of anxiolytics (anti-anxiety medications).
This study reported an increase in prescribing rates for ADHD medications in line with other epidemiological studies conducted over a similar time period in countries around the world (Ponizovsky et al., 2014; Treceño et al., 2012; Dalsgaard et al., 2013). It also found an increase in the concomitant prescribing of antidepressants, antipsychotics and hypnotics.
The authors propose that the increased rate of prescription is likely due to improved recognition, awareness and subsequent diagnosis of ADHD (“a previously unrecognised disease”) within CAMHS. The high proportion of prescriptions for males may “reflect under-diagnosis of the condition in girls” whose symptoms may not manifest as “disruptive behaviour exhibited at school”, more stereotypically exhibited by boys with ADHD.
Furthermore, the authors note that the increase in prescribing to young adults (16-24) may reflect the fact that ADHD is usually a lifelong condition. They state that during the course of the study “it was recognised that there was an urgent need to develop adult ADHD services” in Ireland.
Strengths and limitations
The greatest strengths of this study lie in its large study size and in its use of pharmacy claims data, which avoid reliance on self-report from patients. This is useful, as memory problems are a symptom of ADHD (Barkley et al., 2010).
However, the use of pharmacy claims data as opposed to patient reported data also presents some limitations. The medication prescribed is not always the medication actually taken. For people with ADHD, remembering to take medication regularly can be very difficult (Gau et al., 2006), and it is made all the more difficult by the fact that prescriptions are rarely longer than a month long. This means that patients have to go through a rather challenging process of requesting a new prescription every month, with enough advance warning for the clinician to write a prescription and for pharmacies to order in the medication. Remembering to order and collect medication in this way is something that ADHD symptoms make particularly difficult (NICE, 2018). This can mean that a patient who is taking a medication one month may then go a whole month or more without medication until the highly administrative process of organising the next prescription is completed.
Future investigations should look more closely at prescription rates for different demographics. We can see that girls and women are receiving treatment far less than men and boys, but we have no data on non-binary patients. We also can’t see if there are any racial or ethnic disparities. It would also be interesting to see whether those treated with ADHD medication from an early age in 2005 require concomitant antidepressants or anxiolytics in 2015, as many patients with late-diagnosed ADHD believe that managing life with untreated ADHD is what gave rise to their anxiety and/or depression.
Implications for practice
The number of children and young adults under the GMS scheme who are taking ADHD medication increased to 4,853 in 2015. Using population estimates (n=1,573,200, Central Statistics Office, 2020) and accounting for the fact that the study sample measured 35.4% of this age group (n=556,913), we can estimate that approximately 0.87% of those aged 0-24 years old in Ireland are being treated for ADHD. This contrasts with worldwide prevalence estimates of 5.29%, suggesting that the disorder is still being under-treated in Ireland (Tatlow-Golden et al., 2016).
The results also found that prescribing was considerably higher for males (78.3% of those receiving prescriptions were male), suggesting that greater awareness of the under-diagnosis and under-recognition of ADHD in females is needed. Overall, we can estimate that approximately 0.19% of people aged under 24 in Ireland are women or girls taking ADHD medication. There needs to be greater awareness of ADHD in girls and women, whose symptoms may not manifest in disruptive behaviour. This will be particularly important for those who make referrals for ADHD assessment, such as teachers and GPs.
The study notes that the low treatment rates in Ireland may be due to requirements that only a specialist can diagnose ADHD and initiate treatment with ADHD medication, which limits the accessibility of treatment. Although CAMHS capacity has increased, other studies have suggested that it does not meet current demands (Department of Health Ireland, 2020). Consequently, many children in Ireland will be living with a condition for which they are unable to get an assessment and treatment, exposing them to the substantial burden and long-term impact of living with undiagnosed ADHD (Asherson, 2012). Moreover, the absence of national ADHD services for adults would prevent medication initiation and titration for those who are too old for CAMHS. These implications are identified by the authors and they themselves conclude that the findings support the need for the development of adult ADHD services and better resourced CAMHS.
From my experience, sustained support during the 16-24-year-old period is essential for patients transitioning from CAMHS to adult services. People of this age often face decisions which can shape their future, but patients with ADHD often have low self-esteem and may make risky or unplanned choices, disproportionately influenced by peer approval or acceptance. Teenagers with ADHD are at a greater risk of recruitment into gangs or becoming (often unknowingly) caught up in violent, exploitative or abusive relationships (Hughes et al., 2015; Guendelman et al., 2016; Wymbs et al., 2017). Without support in place, those moving away from the structure of living at home and attending school can find previously well managed symptoms become harder to cope with. ADHD is a risk factor for addiction, and patients who are struggling may develop a habit of using legal and illegal substances to self-medicate (Carpentier et al., 2017; Glass & Flory, 2010; Silva et al., 2014). As symptoms become harder to control, risky or impulsive behaviours can lead to first contacts with the criminal justice system, where it is estimated that approximately 45% of young offenders have ADHD (see this blog from 2011). Therefore, once Ireland have developed the National Clinical Programme for adult ADHD services, there must be clear policy to ensure a smooth handover process with sustained support in place for patients transitioning from CAMHS to adult services.
Statement of interests
Poppy Ellis Logan has had no collaboration or involvement with this study or its authors, and thus has no conflict of interest.
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