The predictors of parent reported behaviors related to olfactory information processing in children with ADHD

Deficits in olfactory system neurogenesis in neurodevelopmental disorders

The role of neurogenesis in neurodevelopmental disorders (NDDs) merits much attention. The complex process by which stem cells produce daughter cells that in turn differentiate into neurons, migrate various distances, and form synaptic connections that are then refined by neuronal activity or experience is integral to the development of the nervous system. Given the continued postnatal neurogenesis that occurs in the mammalian olfactory system, it provides an ideal model for understanding how disruptions in distinct stages of neurogenesis contribute to the pathophysiology of various NDDs. This review summarizes and discusses what is currently known about the disruption of neurogenesis within the olfactory system as it pertains to attention-deficit/hyperactivity disorder, autism spectrum disorder, Down syndrome, Fragile X syndrome, and Rett syndrome. Studies included in this review used either human subjects, mouse models, or Drosophila models, and lay a compelling foundation for continued investigation of NDDs by utilizing the olfactory system.

Abnormalities of structural covariance networks in drug-naïve boys with attention deficit hyperactivity disorder

The aim of this study is to investigate whether the anatomical organization of large-scale brain systems would change in ADHD patients compared to healthy controls. We utilized a structural covariance network (SCN) mapping approach to investigate large-scale networks in 30 drug-naïve ADHD boys and 30 gender- and age-matched controls. The regions showing significant between-group differences in gray matter (GM) volume were defined as seed regions of interest. Then, the SCNs derived from these seeds were statistically compared between ADHD and controls. Significant regional GM volume decreases (P<0.05, corrected) were observed in the right insula and the right orbito-frontal cortex (OFC) in ADHD relative to controls. Both SCNs derived from these two seeds showed more localized topology in ADHD group. Furthermore, significantly decreased structural connectivity were found between insula and right hippocampus, bilateral olfactory cortex, and between OFC and bilateral caudate nucleus (P<0.05, corrected) in ADHD group. Significantly increased association was observed between insula and left middle temporal gyrus (P<0.05, corrected) in ADHD group. Taken together, our results reveal abnormal regional brain anatomy as well as aberrant structural covariance networks in ADHD, supporting previous findings of dysfunction in distributed network organization in patients with ADHD.

Parents reported oral sensory sensitivity processing and food preference in ADHD

Oral sensory processing in children with attention deficit hyperactivity disorder (ADHD) is an area with limited research. Oppositional defiant disorder (ODD) and separation anxiety disorder (SAD) symptoms usually co-occur with ADHD. This study investigates the association of oral sensory processing problems with ODD and SAD symptoms in children with ADHD. The parents of 189 children with ADHD completed Oral Over- and Underresponsivity Behaviors Inventory reporting oral overresponsivity (OR) and underresponsivity (UR) of their children. Only ODD score predicted OR scale score. None of ADHD severity, anxiety score, age and gender predicted OR score. UR scale score was only predicted by SAD and inattention scores. ODD score and hyperactivity/impulsivity score did not predict UR score. The ODD behaviour in children with ADHD needs to be evaluated and managed more extensively and it should include oral sensory occupational therapy. Future studies should extend this research to children with ADHD and obesity and food reward system.

Smell identification function in children with attention deficit hyperactivity disorder

OBJECTIVE

Deficits in olfactory function are common features in neurodegenerative and neuropsychiatric disorders. Olfactory processing is related to dopamine metabolism and orbitofrontal cortex functioning, both known to be involved in the neurobiology of ADHD. Some investigations suggested alterations in olfactory processing (identification and detection threshold) in patients with ADHD. Despite increasing knowledge, controversy about this topic still exists regarding children with ADHD. This study was conducted to help elucidate some of this controversy.

METHODS

50 participants (8-15 years, mean=10.70±1.77) with ADHD were compared to 50 controls. The two groups were well matched for age, gender and Mean School Scores (MSS). We assessed odor identification and threshold through a smell test composed of two tests of identification and detection threshold. Odor detection threshold was assessed with the odorant phenyl ethyl alcohol solved in propylene glycol using a single staircase method. Odor identification was assessed with chemical essences of five common odorants.

RESULTS

The mean Sensory Identification Score for children with ADHD and the control groups were 3.76 (1.06) and 4.46 (0.76), respectively (p<0.001). The mean for Sensory Threshold Score for ADHD and control group was 6.4 (3.35) and 9.75 (2.16), respectively (p<0.001).

CONCLUSION

This study replicated altered olfactory performance in ADHD. Substantial olfactory deficits across the two domains of identification and detection threshold are observed in children with ADHD. These deficits do not seem to be a result of olfactory task difficulty and are not influenced by age, gender and MSS. Further studies are required to investigate whether olfactory function can be used as a biological marker for early diagnosis, treatment and prognosis of ADHD.

Predictors of postural stability in children with ADHD

OBJECTIVE

As children with ADHD who have more inattention problems are more frequently with fine motor problems, it is not clear whether postural balance problems are associated with different subtypes of ADHD. This study investigates the predictors of postural stability in children with ADHD considering the covariant factors of age, gender, and comorbidities.

METHOD

A total of 103 children with ADHD are studied using Poor Postural Stability Questionnaire filled out by their parents.

RESULTS

Linear regression analysis indicates that only oppositional-defiant behavior score is the predictor of seeking-movement subscale score. ADHD type does not predict the score of avoiding-postural-instability subscale, whereas separation anxiety score did so.

CONCLUSION

ADHD subtypes do not have distinct clinical profiles of the balance problems. Postural stability in children with ADHD depends on the comorbid psychiatric disorders rather than ADHD subtypes.