The present study examined pain perception in children and adolescents with ADHD and the interaction between pain perception and the administration of methylphenidate (MPH) in order to generate hypotheses for further research that will help to clarify the association between ADHD diagnosis, MPH treatment and pain perception.
Wolff et al Child Adolesc Psychiatry Ment Health (2016) 10:24 DOI 10.1186/s13034-016-0112-9 RESEARCH ARTICLE Child and Adolescent Psychiatry and Mental Health Open Access Reduced pain perception in children and adolescents with ADHD is normalized by methylphenidate Nicole Wolff1*, Katya Rubia2, Hildtraud Knopf3, Heike Hölling3, Julia Martini1, Stefan Ehrlich1 and Veit Roessner1 Abstract Background: The present study examined pain perception in children and adolescents with ADHD and the interac‑ tion between pain perception and the administration of methylphenidate (MPH) in order to generate hypotheses for further research that will help to clarify the association between ADHD diagnosis, MPH treatment and pain perception Methods: We included 260 children and adolescents of the “German Health Interview and Examination Survey for Children and Adolescents” (KiGGS) and analyzed parent’s assessments of children’s pain distribution and pain percep‑ tion, as well as the influence of MPH administration on pain perception in affected children and adolescents Results: Pain perception was associated with ADHD and MPH administration, indicating that children and adoles‑ cents suffering from ADHD without MPH treatment were reported to have lower pain perception compared to both, healthy controls (HC) and ADHD patients medicated with MPH Conclusion: We suggest that reduced pain perception in children and adolescents with ADHD not medicated with MPH may lead to higher risk tolerance by misjudgments of dangerous situations, expanding the importance of MPH administration in affected children and adolescents Keywords: ADHD, Methylphenidate, Pain, Opioid system, Dopamine Background Attention deficit hyperactivity disorder (ADHD) is characterized by the core symptoms of inattention, hyperactivity and impulsivity [1] and has a higher prevalence (OR = 4.80) among boys compared to girls [2, 3] Neuropsychological dysfunctions in ADHD are a matter of ongoing debate, emphasizing deficits e.g in response inhibition, vigilance, timing and working memory [4– 6] Neural pathways underlying these deficits point to deficits within frontal-subcortical catecholaminergic networks, involving dopaminergic and noradrenergic innervation [1, 5] Hence, deficits in dopaminergic neurotransmission seem to be highly relevant for the neurobiology and therefore targets of medication of ADHD *Correspondence: nicole.wolff@uniklinikum‑dresden.de Department of Child and Adolescent Psychiatry, Faculty of Medicine, TU Dresden, Fetscherstrasse 74, 01307 Dresden, Germany Full list of author information is available at the end of the article Low-dose psychostimulants, including methylphenidate (MPH) and amphetamines are the most widely used medications for ADHD [7] MPH has been shown to substantially reduce core symptoms of inattention, hyperactivity and impulsivity in up to 70 % of affected children [8, 9] However, there are also negative effects of MPH e.g on sleep behavior, i.e some authors found MPH treatment associated sleep-onset difficulties in patients with ADHD of all ages [10, 11] Despite consistent evidence that low doses of MPH influence dopaminergic deficits in the brain [1, 12], neural mechanisms underlying its clinical action are not entirely understood at present [12] Growing evidence suggests that dopamine is involved not only in ADHD core symptoms but also in other perceptive deficits, such as color perception [13], time perception [6, 14, 15] and pain perception [16] Furthermore, the dopamine system is also closely interrelated with the opioid system, which plays a crucial role in pain © 2016 The Author(s) This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated Wolff et al Child Adolesc Psychiatry Ment Health (2016) 10:24 perception as well as reward and motivation [17] The opioid and dopamine systems interact closely in their mediation of reward and motivation, which have been shown to be abnormal in ADHD [18] In addition, there is emerging evidence that the opioid system is associated with impulsiveness in animals and humans [19] and with the mechanism of action of stimulant medication [20, 21] Given the close interaction between these two systems, evidence for associations between the opioid system and both ADHD and stimulant mechanism of action, raises the question whether pain perception that is mediated by the opioid system may also be altered in ADHD In fact, in daily clinical care altered pain perception, particularly in younger children with ADHD, has often been observed For example, an association between growing pain and childhood restless leg syndrome was observed, and it was shown that this effect was more often observed in children with ADHD as compared to controls [22] However, to the best of our knowledge, only two studies examined pain perception in children with ADHD [23, 24] Scherder et al [23] tested pain perception in 50 children and adolescents with ADHD, their unaffected siblings and HC [23], assessed through the children’s pain inventory The study found no differences in pain perception in children and adolescents with and without ADHD However, the 35 unaffected siblings of children and adolescents with ADHD reported reduced intensity and emotionality of past pain experiences compared to the unrelated HC [23] The authors suggested that the long-term exposure of non-affected siblings to the “physical aggressiveness of their affected siblings” might have resulted in the observation of lower pain perception in the non-affected siblings [23] Unfortunately, medication status of children and adolescents with ADHD during the period when pain experience was assessed was not considered which might have masked possible group differences in pain perception In the second part of the study, children and adolescents with ADHD and their unaffected siblings gave blood for genetic analysis and were asked to assess the intensity and emotionality of perceived pain after the venipuncture For this analysis, children and adolescents were requested to abstain from taking medication for at least 48 h Children and adolescents with ADHD compared to non-affected siblings reported reduced pain perception The second study, inducing experimentally pain in adolescents with ADHD [24] analyzed whether there is an association between subjective and physiological responses to pain and the presence of a comorbid conduct disorder (CD) in adolescents with ADHD They analyzed adolescents with pure ADHD in comparison to adolescents with ADHD plus CD and measured pain perception through thermal Page of 10 heat on the skin of the palm of the hand In addition, they collected the skin conductance level (SCL) and questionnaire reports on self-reported pain threshold and pain tolerance times It was observed that although adolescents with ADHD plus CD vs adolescents with pure ADHD reported significantly increased pain threshold time and tolerance, the physiological response and SCL was similar in both groups It was thus emphasized that it is important to consider comorbidities of ADHD when developing interventions Moreover it was argued that it is important to bear in mind the interaction between aggression, antisocial behaviour, conduct disorder, and pain in the ADHD population [24] Two further studies investigated pain perception in adults with ADHD, both finding enhanced pain [16, 25] One study reported increased pain perception in a small sample of 25 adults with ADHD relative to 23 controls, assessed via a numerical pain rating scale, as well as more widespread pain, analyzed using a so-called pain drawing procedure [26] Using a motor function neurological assessment (MFNU) in addition, they observed also that adults with ADHD compared to controls had motor inhibition problems and heightened muscle tone e.g in the latissimus dorsi and calf muscles [25] Pain location and pain levels were furthermore positively correlated with the total score on the MFNU, indicating that the pain reported in the ADHD group might be a consequence of their muscle tone dysregulation and motor inhibition problems [25] However, most patients were responders to stimulant medication and the study did not state how many or whether any of the patients were medication-naive In the other study on pain perception in 30 adults with ADHD, pain was experimentally induced by 1 °C cold water Adults with ADHD were more sensitive to pain [16] but pain perception was modified by MPH: adults with ADHD without MPH medication displayed lower pain threshold, i.e a shorter interval from cold water exposure to the beginning of pain, and reduced pain tolerance, i.e shorter interval participants can bear up against pain, in comparison to both, participants with ADHD medicated with MPH and HC In summary, pain perception seems to be altered in ADHD and to be influenced by the administration of MPH Interestingly, although direct associations have not been investigated at this point, it can also be assumed that alterations in pain perception in ADHD may also be treated by the help of Neurofeedback [27, 28] Here, frequencies in the alpha (about 10 Hz) and in the delta band (about 1–3 Hz) have been shown to influence muscle contraction as well as pain perception, which might also help to normalize pain perception in ADHD Similarly, training of mindfulness has been associated with Wolff et al Child Adolesc Psychiatry Ment Health (2016) 10:24 improvements in self-regulation of attention in ADHD [29] as well as with increased body perception Thus a range of mind–body approaches may also be used in the management of altered pain perception [30] All these treatments may thus be of benefit in the treatment of ADHD (both reduction of core symptoms and improvement of pain perception) However, studies on pain perception have been inconclusive, with one study in children reporting no differences in past pain but reduced perception of induced pain between children with ADHD and HC [23], one study in adolescents comparing adolescents with pure ADHD and those with ADHD and comorbid CD reported similar physiological pain perception but decreased reported pain perception in adolescents with ADHD and CD as compared to adolescents with pure ADHD [24] and the two adult studies reporting enhanced pain perception [16, 25], which furthermore appeared to be modified/normalized by MPH [16] The conflicting findings may be due to low power in small sample sizes or differential pain perception in different age groups of ADHD patients However conflicting findings between studies could also be a result of differences in applied diagnostic criteria (DSM IV vs DSM vs ICD 10) It has for example been observed that the manifestation of ADHD subtypes differs (i) between adolescents and adults and (ii) through the application of different diagnostic systems Moreover, the diagnosis of ADHD as well as common comorbidities, for example autism spectrum disorders (ASD) differs depending on the diagnostic system used The purpose of the present study was to generate hypotheses for further research that will clarify the association between ADHD diagnosis, MPH treatment and pain perception Thus we analyzed this research question in a large, representative sample of German children and adolescents Although altered pain perception has been observed recurrently in children with ADHD in clinical praxis, to the best of our knowledge, no large-scale study has tested (1) pain distribution and pain perception in children with ADHD compared to that of HC and (2) the effect of MPH treatment on pain perception differences Since alterations in pain perception, the mode of action of MPH and the neurochemical changes underlying ADHD are all linked to dopaminergic deficits in the brain, we hypothesized that pain perception would differ between children and adolescents with ADHD relative to HC and between medicated and non-medicated patients with MPH Furthermore, given evidence that age and gender have an impact on pain perception [31–33], we also tested the effects of these two variables on potential group differences Page of 10 Methods The present study analyzed data from the German Health Interview and Examination Survey for Children and Adolescents called “KiGGS’’ KiGGS represents a nationwide, representative cross-sectional health interview and examination survey conducted in Germany from May 2003 until May 2006 by the Robert Koch Institute (RKI) The KiGGS study surveyed 17,641 children and adolescents aged from birth to 17 years from 176 cities and municipalities across Germany The children and adolescents were physically examined and the father and/ or mother (depending on which parent accompanied the child) as well as children over the age of 11 years completed a questionnaire covering psychological and social assessment The study is fully compliant with the Declaration of Helsinki and was approved by the ethics committee at the University Hospital—Charité in Berlin and the Federal Office for the Protection of the Data Signed informed consent was obtained from the primary caregivers of all study participants and also from all adolescents of 14 years or above KiGGS consisted of a core survey (on which we access in the present study) and five additional subsample modules (on which we not further refer here) Within KiGGS several self-administered questionnaires collecting data according to i.e physical health, behavioral and emotional problems, social determinants of health, health-related behavior, health care service utilization and socio demographics were designed by the RKI More details according to further objectives, design and measurements of KiGGS were reported elsewhere [34] We focused on participants with available information regarding ADHD diagnosis, MPH medication, information about pain during the last 3 months, as well as “pain perception” (see the column “pain perception sample” in Table 1) Sixty-five participants met all these criteria (see participants of the category “ADHD with MPH” within the pain perception sample) and were compared to sixtyfive unmedicated ADHD participants randomly selected from the remainder of the sample (n = 115) In addition, a similarly sized age-matched healthy control group without ADHD diagnosis and without any medication was randomly selected out of the remaining pain perception sample (n = 2687) In sum, the analyzed group (refer to the column with the heading “study sample” in Table 1) contains of 260 participants (50.0 % ADHD, 25.0 % MPH medicated, 70.8 % male) in the age range between and 10 years (47.7 %), 11–13 years (31.5 %) and 14–17 years (21.2 %) Among those diagnosed with ADHD, 98 (75.4 %) were male and 32 (24.6 %) were female For more details concerning the substitution of our sample, see Table 1 3196 (24.9 %) χ2 = 124.86, df = 3, p