The long-term MTA study
The so-called MTA study (Multimodal Treatment Study of ADHD) is key to understanding the current state of knowledge (3). The study was initiated in 1994 because substantial use was being made of central nervous system stimulants in ADHD treatment, and yet treatment studies were of poor quality and limited duration.
In the first phase of the study, 579 children (7–10 years) were followed for 14 months after being randomised to four different treatment groups (3). Group 1: an especially systematic pharmacological intervention with monthly specialist follow-up. Group 2: an intensive behavioural therapy programme aimed at home and school. Group 3: a combination of the treatment in group 1 and group 2. Group 4: treatment as usual in the health service, which often entailed less systematic pharmacological therapy.
The six endpoints were adult-reported ADHD symptoms, internalising and externalising symptoms, and the functional measures academic achievement, adult-child interaction, and social skills with respect to peers.
In 1999, the first results from the MTA study revealed a greater reduction in ADHD symptoms in group 1 and group 3 (medication and combined treatment) than in group 2 and group 4 (behavioural therapy and treatment as usual) (3). The addition of behavioural therapy in group 3 produced no statistically significant improvement in symptoms relative to group 1. This result received widespread media attention and was a key justification for the extensive pharmacological treatment of ADHD from the year 2000 onwards (3).
However, after the initial randomised phase, the MTA study continued as an observational study in which 500 children and a control group of 300 children were followed for a further 14 years. The key finding here is that the superior efficacy of systematic medication over the first 14 months disappeared over the course of the next two years (3, 8). Subsequent analyses showed that the combined treatment in group 3 was superior with respect to a composite endpoint consisting of symptoms and functional measures, and that combined treatment in group 3 that led to improvements in parental discipline style could completely normalise behavioural patterns (3).
After six years, the patients who received behavioural therapy alone (group 2) had lower rates of anxiety and depression (4.3 %) than the medication group (19.1 %), the combined treatment group (17.7 %) and the treatment as usual group (16.4 %) (8). In a review, the MTA researchers also concluded that only the combined treatment helped families with the lowest socioeconomic status and reduced the doses of medication required (3).
In spring 2017, the MTA researchers published their latest results (4). The conclusion, 16 years after the start of the study, is that long-term use of central nervous system stimulants is associated with suppression of adult height (1–2 cm on average), but no reduction in symptoms. However, these findings have not had the same impact as the initial results from 1999.