Attention-deficit hyperactivity disorder (ADHD) is associated with high risks of adverse academic outcomes. A major motivation for initiating pharmacological treatment of ADHD is to mitigate these risks; however, the evidence regarding its long-term effects is inconclusive.

Our objective was to investigate the long-term causal effects of pharmacological treatment of ADHD on school grades in Norwegian children and adolescents.

We analysed individual-level registry data of all Norwegians aged 5–15 years in 2009–2011 who were diagnosed with ADHD during this period (n = 6255). Treatment was measured as cumulative ADHD medication prescriptions from time of diagnosis to graduation from mandatory schooling (tenth grade). Outcomes included final grades in nine main school subjects, grade point average and non-assessment (exemption, no basis for assessment). We estimated ordinary least squares (OLS) and instrumental variable models. By exploiting naturally occurring variation in treatment practices, instrumental variable analysis can address residual confounding and estimate causal effects for patients ‘on the margin of treatment’, i.e. those prone to varying treatment practices.

OLS analysis indicated that pharmacological treatment for ADHD was associated with slightly improved grade point average (0.05, 95% CI 0.02–0.09; grade point average s.d. 0.94). Instrumental variable analysis indicated no causal effect of pharmacological treatment on grade point average (−0.01, Anderson−Rubin 95% CI −1.13 to 0.15), individual school subjects or non-assessment.

For children and adolescents on the margin of pharmacological treatment for ADHD, we found no causal effect of pharmacological treatment on any of our measures of academic performance. Although further research is needed, this finding should be considered in the context of clinical decision-making and treatment planning.

Children and adolescents with attention–deficit hyperactivity disorder (ADHD) have a higher likelihood of contact with child welfare services (CWS). Evidence on whether pharmacological treatment of ADHD reduces such contact is limited.

To estimate the causal effect of pharmacological treatment of ADHD on CWS contact.

In this quasi-experimental study, we used nationwide registry data covering all individuals aged 5–14 years and diagnosed with ADHD during 2009–2011 in Norway. We used linear probability models and instrument variable analyses to estimate the associations and causal effects of pharmacological treatment on CWS contact up to 4 years after diagnosis. As instrument variable analysis uses natural variation in treatment decisions between clinics as pseudo-randomisation, estimates inform effects for children and adolescents at the margin of treatment, i.e. patients whose treatment is more influenced by variation in treatment practice, e.g. due to less severe or atypical symptom presentation.

A total of 5930 children and adolescents aged 5–14 years were diagnosed with ADHD between 2009 and 2011 (mean (s.d.) age 10.1 (2.4) years; 4380 males (73.9%)). Instrument variable analyses showed a reducing effect of pharmacological treatment on the use of supportive interventions by 11.9 percentage points (95% CI: −20.12, −3.80) and out-of-home-placement by 3.30 percentage points (95% CI: −6.44, −0.15) at 2-year follow-up. This corresponds to the numbers needed to treat estimates of 8 and 30, respectively.

Pharmacological treatment of ADHD reduces CWS contact among children and adolescents at the margin of treatment, lowering the probability of receiving supportive interventions and out-of-home placements. Findings suggest that medication reduces behavioural symptoms, which may improve the family coping mechanism and reduces the need for CWS involvement.

ISRCTN11891971.

There are now hundreds of systematic reviews on attention deficit hyperactivity disorder (ADHD) of variable quality. To help navigate this literature, we have reviewed systematic reviews on any topic on ADHD.

We searched MEDLINE, PubMed, PsycINFO, Cochrane Library, and Web of Science and performed quality assessment according to the Joanna Briggs Institute Manual for Evidence Synthesis. A total of 231 systematic reviews and meta-analyses met the eligibility criteria.

The prevalence of ADHD was 7.2% for children and adolescents and 2.5% for adults, though with major uncertainty due to methodological variation in the existing literature. There is evidence for both biological and social risk factors for ADHD, but this evidence is mostly correlational rather than causal due to confounding and reverse causality. There is strong evidence for the efficacy of pharmacological treatment on symptom reduction in the short-term, particularly for stimulants. However, there is limited evidence for the efficacy of pharmacotherapy in mitigating adverse life trajectories such as educational attainment, employment, substance abuse, injuries, suicides, crime, and comorbid mental and somatic conditions. Pharmacotherapy is linked with side effects like disturbed sleep, reduced appetite, and increased blood pressure, but less is known about potential adverse effects after long-term use. Evidence of the efficacy of nonpharmacological treatments is mixed.

Despite hundreds of systematic reviews on ADHD, key questions are still unanswered. Evidence gaps remain as to a more accurate prevalence of ADHD, whether documented risk factors are causal, the efficacy of nonpharmacological treatments on any outcomes, and pharmacotherapy in mitigating the adverse outcomes associated with ADHD.