Temperament Dimensions and Awakening Salivary Cortisol Levels in ADHD.
Condition: Attention Deficit Hyperactivity Disorder
MeSH terms: Hyperkinesis; Attention Deficit Disorder with Hyperactivity
Study type: Observational

Summary: 
      To analyze heterogeneity in ADHD experts in last decade advised to look beyond the lists of
      existing symptoms towards phenotypic measures that can be represented dimensionally and have
      well-theorized relationships with neurobiological systems, (Sonuga-Barke & Halperin, 2010;
      Insel et al, 2010; Fair D, Bathula D, Nikolas M, Nigg JT, 2012; Georgiades S, Szatmari P,
      Boyle M, 2013; Sanislow CA, Pine DS, Quinn KJ, et al, 2013). This is the nucleus of RDoC aims
      because children and adolescents with ADHD can be characterized in terms of several features
      that are best represented as dimensions and have well-theorized relationships to biological
      systems (Cuthbert & Insel, 2013).
    

Detailed description: 
      Recently evidence suggests that measures of child temperament may predict ADHD symptoms
      (Einziger et al., 2018). Temperament is a characteristic of personality (Buss & Plomin, 1984;
      Crowell, 2016) and refers to individual, neurobiologically-based difference in reactivity,
      self-regulation and cognition (Eisenberg, 2012).

      It has been previously emphasized (Nigg J., 2016), that Hypotalamic-Pituitary-Adrenal (HPA)
      axis, through the cortisol hormone, may represent a powerful biological measure of
      behavioural self-regulatory systems, activity level, cognition, temperament (Stadler et al,
      2011; Martel et al., 2009; Sonuga-Barke, 2005) and arousal (Snoek, Van Goozen, Matthys,
      Buitelaar, & Engeland, 2004). Cortisol is released from the surrenal gland by means of the
      HPA axis activation, in response to catecholaminergic neurotransmitters (Ulrich-Lai & Herman,
      2009). Cortisol is involved in the regulation of a wide range of body functions, including
      emotion processing (Skosnik, Chatterton, Swisher, & Park, 2000), awakening (Fries,
      Dettenborn, & Kirschbaum, 2009) and stress responses (Chrousos, Kino, & Charmandari, 2009).

      Both cortisol and temperament may share self-response regulatory processes (Martel et al.,
      2008; Nigg, 2016; Ulrich-Lai & Herman, 2009), and one study on 70 healthy pre-schoolers
      indicates that children with SE temperament has higher morning salivary cortisol levels
      during their first week of a new primary school year (Davis, Donzella, Krueger, & Gunnar,
      1999), hypothesized as a stress-induced effect.

      To date, no studies have been conducted to study heterogeneity starting from the
      self-response regulatory processes between temperament and cortisol in children and
      adolescents with ADHD.

      As for clinical application of HPA-axis and cortisol level in ADHD diagnosis and dimension,
      available studies are, as yet, either inconsistent (Bonvicini, Faraone, & Scassellati, 2016;
      Freitag et al, 2009, Corominas et al, 2012) or suggestive, but not significant, upon
      dimensional stratification of ADHD symptoms (Pinto et al., 2016).

      The aims of this study to contribute to the issue of clinical heterogeneity of ADHD,
      analysing whether ADHD symptoms and co-morbidity traits simultaneously link to both cortisol
      level and temperament dimensions, as biomarkers of arousal and inhibited behaviour. To pursue
      our aim we formulated five specific research questions: i) Do temperament dimensions and
      awakening cortisol level differ between children and adolescents with ADHD and TDC? ii) Do
      temperament dimensions and awakening cortisol levels correlate with dimension of ADHD core
      symptoms? iii) Does awakening cortisol level associate with any of the three-temperament
      dimension? iv) Do parent ratings of the oppositional and defiant traits and anxiety traits
      affect the association between temperament dimensions and cortisol levels with ADHD core
      symptoms in the ADHD group?
    

Intervention name(s): Swanson, Noolan and Phelham - IV edition (SNAP-IV); Conners' Parent Rating Scales (CPRS)
Intervention type(s): Diagnostic Test
Intervention description(s): Ratings on the Swanson, Nolan and Pelham Evaluation Scale - IV (Bussing et al., 2008), were assessed during baseline visit for participants at the time of research assessment, to exclude the presence of ADHD symptoms in the healthy subjects. This scale is composed of 26 items for ADHD symptoms and ODD and was administered at baseline and at follow-up visit.
Temperament assessment: we used the Mary Rothbart's Temperament Questionnaire, a caregivers' report measure designed to provide a detailed assessment of temperament.
ADHD Rating scales: the Long Version of Conners' Parent Rating Scale (Conners et al., 1998) was used to quantify ADHD comorbidity symptoms, as ODD and Anxiety traits, in the children and adolescents with ADHD.
Salivary cortisol: Sampling was performed during one ordinary weekday between 7 and 8 o'clock, within 60' after nocturnal awakening.
Other intervention name(s): Rothbart Temperament questionnaires
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        We enrolled 67 individuals with ADHD and 70 typically developing youths (TDY) aged between
        4 and 16 years. Individuals with ADHD were recruited from the Child and Adolescent
        Neuropsychiatry Unit, University of Sassari, Italy.
      
Biospecimen description: 
      Saliva sample to tests awakening cortisol levels.