Do the ADHD subtypes exist on a physiological continuum? A reply to Reiersen and Todorov (2013)

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Scandinavian Journal of Child and Adolescent Psychiatry and Psychology

Psychiatric Research Unit, Region Zealand

Ole Jakob Storebø

Subject: Medicine

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VOLUME 4 , ISSUE 3 (December 2016) > List of articles

Do the ADHD subtypes exist on a physiological continuum? A reply to Reiersen and Todorov (2013)

Keith Fluegge *

Citation Information : Scandinavian Journal of Child and Adolescent Psychiatry and Psychology. Volume 4, Issue 3, Pages 107-108, DOI: https://doi.org/10.21307/sjcapp-2016-016

License : (CC BY-NC-ND 4.0)

Published Online: 22-December-2016

ARTICLE

ABSTRACT

To the Editor:

Reiersen and Todorov (1) published their findings exploring the relationship between the various subtypes of attention-deficit/hyperactivity disorder (ADHD) and related psychopathologies in a large population-based sample of adolescents and children. The authors reported that subjects who presented with symptoms from both the inattentive subtype and the hyperactive subtype experienced a greater severity of co-occurring psychopathology. This led the authors to conclude that, although the continued clinical use of ADHD subtypes may be appropriate, these distinct diagnostic subtypes may be resulting in a failure to identify an important subgroup of ADHD patients—those who experience symptoms from both subtypes—and thus potentially leading to more severe psychopathological outcomes. The authors advised that upcoming editions of the Diagnostic and Statistical Manual of Mental Disorders be revised to include a diagnostic category of ADHD “not elsewhere classified.”

In support of this idea, another recent meta-analysis qualified the role of hyperactivity in patients with ADHD (2) and indicated that hyperactivity may not be a ubiquitous feature of ADHD. Rather, its manifestation may be particularly dependent on environmental factors, including cognitive functioning demands. Prolonged cognitive load has been associated with sympathetic hyperactivity in healthy humans (3). Given that medication-naïve patients with ADHD experience parasympathetic overarousal (4), it may be that excessive motor activity is associated with sympathetic mechanisms that are affected by changing cognitive demands (5).

Other recent findings have corroborated an association between air pollution and childhood behavior problems (6). It has subsequently been suggested that chronic environmental exposure to the widespread and underestimated air pollutant nitrous oxide (N2O) may be the primary etiologic factor in neurodevelopmental disorders like ADHD (7-9). Subanesthetic and subanalgesic N2O exposures in humans have been characterized by impairments in attention and working memory (10,11) as well as by the induction of a parasympathetic dominant state (8), thereby suggesting that a compensatory hyperkinetic state may reverse these physiological effects (3,5).

When considering the role of hyperactivity in ADHD for the facilitation of sympathetic resuscitation, it may be important to consider the spontaneously hypertensive rat, which is a validated model of ADHD (12) before the onset of hypertension (i.e., sympathetic overflow) (13). It may therefore be reasonable to speculate that a hyperactive state precedes (in spontaneously hypertensive rats) and possibly potentiates (in humans) sympathetic resuscitation. This would imply that the various ADHD subtypes may not be exclusive conditions; rather, the subtypes may exist on a continuum in a significant contingent of patients with ADHD, as Reiersen and Todorov have found (1). Therefore, chronic environmental N2O exposure may lead to attention deficits and a parasympathetic dominance, whereas a hyperkinetic phenotype may be a compensatory mechanism of sympathetic and cognitive resuscitation. However, a recent meta-analysis contradicts the notion of autonomic dysregulation and parasympathetic dominance in patients with ADHD (14). Therefore, the relationship between the ADHD subtypes and chronic environmental N2O exposure warrants further clarification to understand whether the subtypes exist on a physiological continuum in response to environmental exposure to N2O.

Notes

[1] Conflicts of interest Conflicts of interest

The author declares no conflict of interest.

[2] Contributed by Disclosure

Similar manuscripts related to this hypothesis may be under review, in press or published elsewhere, although the specific content contained in this manuscript is original and not in review or previously published. Relevant prior works are cited.

References


  1. Reiersen AM , Todorov AA . Exploration of ADHD subtype definitions and co-occurring psychopathology in a Missouri population-based large sibship sample. Scand J Child Adolesc Psychiatr Psychol 2013;1(1):3-13.
  2. Kofler MJ , Raiker JS , Sarver DE , Wells EL , Soto EF . Is hyperactivity ubiquitous in ADHD or dependent on environmental demands? Evidence from meta-analysis. Clin Psychol Rev 2016;46:12-24.
  3. Mizuno K , Tanaka M , Yamaguti K , Kajimoto O , Kuratsune H , Watanabe Y . Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity. Behav Brain Funct 2011;7:17.
  4. Negrao BL , Bipath P , van der Westhuizen D , Viljoen M . Autonomic correlates at rest and during evoked attention in children with attention-deficit/hyperactivity disorder and effects of methylphenidate. Neuropsychobiol 2011;63:82-91.
  5. Sterling M , Jull G , Wright A . Cervical mobilisation: concurrent effects on pain, sympathetic nervous system activity and motor activity. Man Ther 2001;6(2):72-81.
  6. Forns J , Dadvand P , Foraster M , et al . Traffic-related air pollution, noise at school, and behavioral problems in Barcelona schoolchildren: a cross-sectional study. Environ Health Perspect 2016;124:529-35.
  7. Fluegge K . Do toxic synergies of underlying etiologies predispose the positive association between traumatic brain injury and ADHD? J Atten Disord 2016; doi: 10.1177/1087054716633858.
  8. Fluegge K . The possible role of air pollution in the link between ADHD and obesity. Postgrad Med 2016; doi: 10.1080/00325481.2016.1189802.
  9. Fluegge K , Fluegge K . Glyphosate use predicts healthcare utilization for ADHD in the Healthcare Cost and Utilization Project net (HCUPnet): A two-way fixed-effects analysis. Pol J Environ Stud 2016;25(4):1-15.
  10. Fagan D , Paul DL , Tiplady B , Scott DB . A dose-response study of the effects of inhaled nitrous oxide on psychological performance and mood. Psychopharmacol (Berl) 1994;116:333-8.
  11. Armstrong PJ , Morton C , Sinclair W , Tiplady B . Effects of nitrous oxide on psychological performance. A dose-response study using inhalation of concentrations up to 15%. Psychopharmacol (Berl) 1995;117:486-90.
  12. Sagvolden T , Johansen EB , Wøien G , et al . The Spontaneously Hypertensive Rat model of ADHD – the importance of selecting the appropriate reference strain. Neuropharmacol 2009;57(7-8):619-626.
  13. Russell VA , Sagvolden T , Johansen EB . Animal models of attention-deficit hyperactivity disorder. Behav Brain Funct. 2005;1:9.
  14. Koenig J , Rash JA , Kemp AH , Buchhorn R , Thayer JF , Kaess M . Resting state vagal tone in Attention Deficit (Hyperactivity) Disorder: A meta-analysis. World J Biol Psychiatry 2016:1-15.
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REFERENCES

  1. Reiersen AM , Todorov AA . Exploration of ADHD subtype definitions and co-occurring psychopathology in a Missouri population-based large sibship sample. Scand J Child Adolesc Psychiatr Psychol 2013;1(1):3-13.
  2. Kofler MJ , Raiker JS , Sarver DE , Wells EL , Soto EF . Is hyperactivity ubiquitous in ADHD or dependent on environmental demands? Evidence from meta-analysis. Clin Psychol Rev 2016;46:12-24.
  3. Mizuno K , Tanaka M , Yamaguti K , Kajimoto O , Kuratsune H , Watanabe Y . Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity. Behav Brain Funct 2011;7:17.
  4. Negrao BL , Bipath P , van der Westhuizen D , Viljoen M . Autonomic correlates at rest and during evoked attention in children with attention-deficit/hyperactivity disorder and effects of methylphenidate. Neuropsychobiol 2011;63:82-91.
  5. Sterling M , Jull G , Wright A . Cervical mobilisation: concurrent effects on pain, sympathetic nervous system activity and motor activity. Man Ther 2001;6(2):72-81.
  6. Forns J , Dadvand P , Foraster M , et al . Traffic-related air pollution, noise at school, and behavioral problems in Barcelona schoolchildren: a cross-sectional study. Environ Health Perspect 2016;124:529-35.
  7. Fluegge K . Do toxic synergies of underlying etiologies predispose the positive association between traumatic brain injury and ADHD? J Atten Disord 2016; doi: 10.1177/1087054716633858.
  8. Fluegge K . The possible role of air pollution in the link between ADHD and obesity. Postgrad Med 2016; doi: 10.1080/00325481.2016.1189802.
  9. Fluegge K , Fluegge K . Glyphosate use predicts healthcare utilization for ADHD in the Healthcare Cost and Utilization Project net (HCUPnet): A two-way fixed-effects analysis. Pol J Environ Stud 2016;25(4):1-15.
  10. Fagan D , Paul DL , Tiplady B , Scott DB . A dose-response study of the effects of inhaled nitrous oxide on psychological performance and mood. Psychopharmacol (Berl) 1994;116:333-8.
  11. Armstrong PJ , Morton C , Sinclair W , Tiplady B . Effects of nitrous oxide on psychological performance. A dose-response study using inhalation of concentrations up to 15%. Psychopharmacol (Berl) 1995;117:486-90.
  12. Sagvolden T , Johansen EB , Wøien G , et al . The Spontaneously Hypertensive Rat model of ADHD – the importance of selecting the appropriate reference strain. Neuropharmacol 2009;57(7-8):619-626.
  13. Russell VA , Sagvolden T , Johansen EB . Animal models of attention-deficit hyperactivity disorder. Behav Brain Funct. 2005;1:9.
  14. Koenig J , Rash JA , Kemp AH , Buchhorn R , Thayer JF , Kaess M . Resting state vagal tone in Attention Deficit (Hyperactivity) Disorder: A meta-analysis. World J Biol Psychiatry 2016:1-15.

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