Proefschrift_Holstein

Reward modulation of cognitive function: adult ADHD

ADHD (Faraone et al., 2005; Brookes et al., 2008; Franke et al., 2008; for a review, see Durston et al., 2009; Gizer et al., 2009; Franke et al., 2010). In summary, in this pilot study we tested the hypothesis that effects of reward motivation on task switching and striatal BOLD signal vary as a function of DAT1 genotype adult patients with ADHD, when they were ON relative to OFF their methylphenidate regimen, compared with healthy controls.

Methods Participants

We present data from 23 patients with ADHD (mean + SE age 35.74 + 2.36; 14 men) and 26 healthy control participants (mean + SE age 38.08 + 2.00; 11 men). Patients visited our centre on two occasions, once after intake of methylphenidate and once after withdrawal from methylphenidate. Healthy controls were also tested on two occasions, without any methylphenidate ( procedure ). Initially we recruited 57 participants (29 patients with ADHD and 28 healthy controls) from an ongoing study on ADHD and genetics, IMpACT-NL (Hoogman et al., 2011; Hoogman et al., 2013; Onnink et al., 2014; www.impactADHDgenomics.com), in which they were tested extensively, genotyped, and diagnosed ( table 4.1 ). Patients were included if they met DSM- IV-TR criteria for ADHD in childhood as well as adulthood. All participants were assessed using the Diagnostic Interview for Adult ADHD (Kooij and Francken, 2007). The Structured Clinical Interviews for DSM-IV (SCID-I and SCID-II) were administered. Assessments were carried out by trained professionals (psychiatrists or psychologists). In addition, a quantitative measure of clinical symptoms was obtained using the ADHD rating scale-IV (Kooij et al., 2005). Exclusion criteria for participants were alcohol or substance addiction in the last 6 months, current psychosis, manic episodes, obsessive compulsive disorder or eating disorders (assessed using SCID-I), full-scale IQ estimate < 70 (assessed using the Wechsler Adult Intelligence Scale-III), neurological disorders, sensorimotor disabilities, and non-Caucasian ethnicity. An additional exclusion criterion for healthy comparison subjects was a current or past neurological or psychiatric disorder according to SCID-I. Three patients did not complete the testing sessions. Two patients were excluded because they did not follow instructions regarding methylphenidate withdrawal and/or intake ( procedure ) and one because of excessive head movement. One healthy control participant was excluded from analysis due to suboptimal quality of the structural data leading to normalization difficulties, and one for meeting the criteria for an ADHD diagnosis according to the ADHD rating scale-IV (Kooij et al., 2005) ( neuropsychological assessment ). Hence, 23 patients with ADHD and 26 healthy controls were included in the final analyses.

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