Using data from a computerised UK primary care database, of the 610 adult patients identified who had started ADHD drug treatment in childhood, 358 (58.7%) of these patients had stopped treatment before the age of 18 years, 252 (41.3%) continued ADHD drug treatment from childhood into adulthood. Also 122 adult patients who had started ADHD drug treatment in adulthood were identified. Data from questionnaires sent to the GPs of a random sample of 50 patients from each of these three distinct patient groups, were used to address issues with ADHD drug treatment from childhood into adulthood (Groups 1 and 2) and in adulthood (Group 3).
A high response rate was achieved in this study ranging from 82% to 94% across the three study groups. There are a number of factors which are likely to contribute to the high response rate: the GPs who contribute data to the THIN database, and who consent to providing additional patient information, are a self-selected group and in addition, those who completed and returned the questionnaire were compensated. A high response rate (>95%) using the THIN database has been reported elsewhere
[18, 22]. These response rates are higher than reported in other GP studies; a review of published GP studies from the early 1990s reported a mean response rate of 61%
. These authors acknowledged that this figure was likely to overestimate the true response rate as many studies with low response rates fail to get published.
Reasons for stopping ADHD pharmacological treatment before adulthood (Group 1)
In the current study, GPs were not aware of the reason for stopping treatment in over one-third of patients. GPs, who were aware of the reason(s), stated that it was the patient’s decision to stop treatment in 56% of cases (14/25 who responded to this question). A qualitative study conducted by Wong et al.
 in which patients were asked directly for reasons for cessation of treatment in adolescence reported in seven out of ten cases, the decision to stop treatment was their own and was often influenced by more than one factor. In addition, some patients who stopped treatment did so because they felt they were able to control themselves better than they could when they were younger, whilst others had gravitated towards environments and employment that did not place the same demands on maintaining focus and concentration.
While it is recognized that symptoms of ADHD decline over time in some patients, the prognosis of ADHD depends on the definition of persistence used
[4, 24]. Studies which have examined the persistence of the condition, using the symptomatic definition of remission, reported that the persistence of ADHD into adulthood was approximately 65%
. This current study was not designed to estimate persistence of ADHD into adulthood, but according to the patients’ GP, three of the 42 patients who stopped treatment before adulthood reported experiencing ADHD symptoms after stopping pharmacological treatment. Hence it may be prudent for GPs to review, on a regular basis, older adolescents who stop medication for ADHD in order to identify if symptoms and impairments return and thus whether these patients require further assessment and/or re-initiation of treatment.
Another reason cited for stopping treatment was the occurrence of side-effects, albeit in a low number of patients (2/25). The three regulatory approved drugs in the UK to treat ADHD have recognised and well established side-effect profiles including (but not limited to) effects on sleep, decreased appetite and the cardiovascular system. Many of the common side-effects of these drugs are transient and subside with time or with reduced dosage, however serious/severe events may warrant discontinuation of treatment. Although there have been some concerns of the safety of ADHD treatment, it is generally accepted that serious adverse reactions are uncommon
[25, 26]. In the present study, details of the nature and severity of the side-effects which resulted in discontinuation of the drug were not reported by the GPs.
Other reasons contributing to patient cessation of treatment which have been cited in the literature include the poor provision of treatment services for older adolescents and young adults. Typically in the UK, patients with ADHD are under the care of child and adolescent mental health services up to the age of 16 years or school-leaving age with GPs responsible for prescribing ADHD medications
. However, ADHD services within the adult mental health system in the UK are currently poorly developed
 and clear arrangements for transition are often lacking
. Wong et al. reported this as a reason for stopping treatment in three out of ten patients interviewed
Psychological treatment for ADHD (Groups 1 & 2)
There are a number of psychological treatments available for patients with ADHD, as an alternative to or in combination with pharmacological treatment. The NICE guidelines acknowledge that there is scant information available on the use of this modality of treatment
. The latest meta-analysis on nonpharmacological interventions for ADHD indicate that better evidence for efficacy from blinded assessments is required for behavioral interventions, neurofeedback and cognitive training before they can be supported as treatments for core ADHD
. Psychological treatments for ADHD are currently likely to be limited to certain areas of the UK where specialist services are available to provide such interventions and this is especially true for adult patients for whom there are few specialist ADHD clinics
In Group 1, GPs responded that 33% of patients received psychological interventions for ADHD following cessation of treatment. In Group 2, 56.3% of patients had ever received psychological therapy in addition to pharmacological treatment for ADHD; 12.5% of patients were currently receiving therapy.
Data from the current study showed great variability between these two groups; however this may be in part due to the small sample size of the individual groups. This variability suggests that psychological treatment may be considered either less favoured or less widely available for the treatment of ADHD.
Treatment of other mental health conditions (Groups 1, 2 & 3)
The treatment of other psychological/psychiatric conditions was investigated in the current study, with results varying across the three patient groups.
The results demonstrate that in this sample of patients, adult patients who initiated treatment for ADHD in adulthood were more frequently treated for other mental health conditions prior to diagnosis of ADHD compared to patients who started pharmacological treatment for ADHD in childhood. The NICE report states that “In adults, coexisting symptoms, syndromes and disorders are frequently found to exist alongside the core ADHD syndrome, but their distinction from ADHD and the reasons for high rates of coexistence are not well addressed in the current literature”
. A recent review paper by Asherson and colleagues highlight the many difficulties associated with the presentation of ADHD in adults, with a particular emphasis on high-functioning individuals, the challenges of current diagnostic criteria, cultural influences on the recognition of the disorder, and the burden of ADHD, both socially and economically, on adults with the disorder
. An interview study, conducted by Matheson and colleagues, examining adult ADHD patients’ experiences of impairment, accessing services and treatment management, reported on the psychosocial burden from a delayed diagnosis of ADHD in adulthood
. Patients had sought help from services in childhood/adolescence due to depression or anxiety, which resulted in years of misdiagnoses and ineffective treatments; many patients attributed the cause of comorbid disorders to underlying ADHD. The effect of the delayed diagnosis was a chronic sense of failure and missed potential in many areas of their lives
Shared-care arrangements (Groups 2 & 3)
NICE guidelines, published in 2008, recommend that “drug treatment should only be initiated by an appropriately qualified healthcare professional with expertise in ADHD and should be based on a comprehensive assessment and diagnosis. Continued prescribing and monitoring of drug treatment may be performed by general practitioners, under shared care arrangements”
. However, although the questionnaire for the current study was administered in 2010, the data obtained related to the study period 2003 to 2008, therefore for the majority of patients, the NICE guidelines were not in place when these patients were receiving treatment. The data from the study revealed that at that time, shared-care was not in place for all patients receiving treatment for ADHD in adulthood (Groups 2 & 3). For those patients in Group 2, who started treatment in childhood/adolescence, fewer than 20% were treated under shared care protocols; however of those patients who started in adulthood (Group 3) approximately 40% of patients had shared care. It was not possible to examine any further differences e.g. geographical differences in the provision of shared care across the UK; however it is recognised that ADHD services within adult mental health care are currently poorly developed in the UK
. NICE also emphasized the benefit that such a service would bring including ‘better care of young people with ADHD during the transition between child and adolescent mental health services (CAMHS) or paediatric services, and adult mental health services’, ‘decreasing the number of people who disengage from services’, and ‘improving the recognition, diagnosis and treatment of ADHD in adults and reducing the risk of misdiagnosis’
. It would be important in future studies to examine the provision of shared care and the impact this has on the delivery of care to patients with ADHD.
Strengths and limitations
This study utilised THIN data to access information on a large cohort of patients with ADHD, across a wide age range, who were treated in primary care. The services provided by THIN also permitted the distribution and retrieval of anonymised questionnaires from GPs which enabled the analysis of information that is not routinely coded in automated databases. The response rate achieved was high, over 80% in all three groups and over 90% in two of the groups. A limitation of the study was the lower proportion of patients in Group 3 (adults who started ADHD treatment in adulthood) who met the study criteria; 73% in this group, compared with 94% in Group 1 and 90% in Group 2. Patients in the latter two groups were identified as having received their first prescription for a study drug in childhood or adolescence and followed forward into adulthood. Patients in Group 3 were also identified from the coded records on the database. However, in responding to the questionnaire, their GPs may have accessed information not coded on the database which indicated an earlier (pre-adulthood) prescription(s) for the treatment of ADHD. Historical data on childhood disorders and their treatment may be missing if patients move practices as adults; this may account for the difference in the number of valid cases between coded information and the response to the questionnaires, and highlights the importance of verifying electronic records with GP questionnaires.
For a number of questions asked, the answers were not known by the GP. This was particularly the case when GPs were asked for the reasons why patients in Group 1 stopped ADHD medication. It should be considered that there may be systematic differences between those patients for whom the reason was known such as engagement with GP, etc. In addition to the small sample sizes in each group, these missing data may be a source of bias to the study. However, the fact that GPs don’t know the reason for cessation of treatment in many cases is important information and reflects management practices for adult ADHD that could be improved upon.
While this study included three cohorts of patients, namely those who stopped ADHD treatment before adulthood, those who started treatment in childhood and continued treatment into adulthood and those who started treatment in adulthood, we were not able to investigate the long-term outcomes of these groups due to the time period of this study. It requires long-term monitoring to examine issues such as the benefits or risks of extended use of pharmacological treatment on symptoms, impairments, and quality of life for adult patients with ADHD.
Finally, although a large database was used to identify patients, the small sample sizes in each group warrants caution if data were extrapolated to the greater UK population.