Identification of neurophysiological biotypes in attention deficit hyperactivity disorder.

AIM: Findings on neurophysiological alterations in attention deficit hyperactivity disorder (ADHD) have been proposed to underlie ADHD symptoms, with different etiological pathways for different patient biotypes. We aimed at determining whether neurophysiological deviations confirm distinct neurophysiological profiles in ADHD, thus providing direct evidence for the endophenotype concept. METHODS: Neurophysiological biotypes were investigated in 87 adult patients with ADHD using cluster analysis. Parameters fed into the analysis comprised both hemodynamic and electrophysiological data. To validate results, the independent variables of the clusters were compared with healthy controls. RESULTS: Cluster analysis yielded three neurophysiologically based ADHD biotypes showing: (i) above-average functioning in attention allocation; (ii) difficulties in attention allocation and inhibitory control but elevated frontal activation during a working memory task; and (iii) functional impairments in state regulation. CONCLUSION: Classifying patients with ADHD into neurophysiological biotypes sheds light on etiological pathways, with implications for diagnostics and (individualized) treatment options.

A randomized-controlled neurofeedback trial in adult attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a childhood onset disorder persisting into adulthood for a large proportion of cases. Neurofeedback (NF) has shown promising results in children with ADHD, but randomized controlled trials in adults with ADHD are scarce. We aimed to compare slow cortical potential (SCP)- and functional near-infrared spectroscopy (fNIRS) NF to a semi-active electromyography biofeedback (EMG-BF) control condition regarding changes in symptoms and the impact of learning success, as well as changes in neurophysiological parameters in an adult ADHD population. Patients were randomly assigned to SCP-NF (n = 26), fNIRS-NF (n = 21) or EMG-BF (n = 20). Outcome parameters were assessed over 30 training sessions (pre, intermediate, post) and at 6-months follow-up (FU) including 3 booster sessions. EEG was recorded during two auditory Go/NoGo paradigms assessing the P300 and contingent negative variation (CNV). fNIRS measurements were conducted during an n-back- as well as a Go/NoGo task. All three groups showed equally significant symptom improvements suggesting placebo- or non-specific effects on the primary outcome measure. Only when differentiating between learners and non-learners, fNIRS learners displayed stronger reduction of ADHD global scores compared to SCP non-learners at FU, and fNIRS learners showed specifically low impulsivity ratings. 30.8% in the SCP-NF and 61.9% of participants in the fNIRS-NF learned to regulate the respective NF target parameter. We conclude that some adults with ADHD learn to regulate SCP amplitudes and especially prefrontal hemodynamic activity during NF. We did not find any significant differences in outcome between groups when looking at the whole sample. When evaluating learners only, they demonstrate superior effects as compared to non-learners, which suggests specific effects in addition to non-specific effects of NF when learning occurs.