A systematic review on olfaction in child and adolescent psychiatric disorders

Abstract

There is substantial evidence that olfactory function may serve as biomarker in adult neuropsychiatric disorders, e.g. overall diminished olfaction in Parkinson's disease as parameter for early pre-motor and differential diagnosis. Here, we present data from a systematic literature review in olfactory function in child and adolescent psychiatric disorders and report two unpublished data sets of autism and obsessive-compulsive disorder. The overall number of olfaction studies is low-even after taking into account adult samples. In addition, heterogeneity of findings is high due to methodological limitations such as the use of different olfactory tests and odours targeting the olfactory and/or the trigeminal system and neglecting possible confounders, e.g., intelligence or oto-rhino-laryngological affections. Despite these limitations, there is some indication for specific alterations of olfactory function especially in disorders with dopaminergic pathology (e.g. attention deficit/hyperactivity disorder, autism, schizophrenia, 22q11 deletion syndrome). Dopamine is a relevant modulator of early processes in the olfactory bulb. Our systematic review provides the basis for future confirmatory studies investigating olfaction as putative biomarker in child and adolescent psychiatric disorders. We further propose studies of thorough and elaborate methodological standards in combination with imaging techniques and the investigation of the influence of genetic variation on olfactory function.

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“…We hypothesize that one of the major reasons for the alarming rise in autism and autism spectrum disorder is the rise in use of fragrances 2 . It should be noted that autism used to be a relatively rare diseases at the turn of the 20th century [2][3][4][5][6][22][23][24] , but it has now been found that 1 out 88 children is suffering from ASD; again, this may be an underestimate. Since a neonate's brain is still developing after birth, we should expect a rise in other neurological but related conditions (e.g.…”

“…Since a neonate's brain is still developing after birth, we should expect a rise in other neurological but related conditions (e.g. attention de icit hyperactive disorder [ADHD], regressive autism; for example, a child is born normal but begins to show signs of autism after 18 months or later) [21][22][23][24] . ASD is a developmental condition characterized by de icits in social interaction, verbal and nonverbal communication and obsessive/stereotyped patterns of behaviour.…”

“…In addition, there is evidence of impoverished language and empathy and a profound inability to adopt another's viewpoint-a failure to construct a 'theory of mind' for interpreting another person's [3][4] . Although there is no reliable neurophysiological marker associated with ASDs, dysfunction of olfactory bulb (OB) and mirror neuron system (MNS) has been documented [3][4]24 . The bars shown in Figure 1 indicate periods when organs are most sensitive to damage from teratogenic agents.…”

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“…Yu-Shiuan Cheng, Ho-Wen Chen, and Yen-Hisun Chuang on similar properties between collecting receptor points and sources substance to exploring the relation on sources and receptor points [11], [12]. Hence, it is unable to identify pollutants characterization exactly.…”