Table 2 Outcome measures assessed for feasibility for RCT

ADHD Symptomatology

Conners Clinical Index (CI) from the Conners Comprehensive Behavior Rating Scales [83].

(1) Parent report

(2) Teacher report

(3) Self-report

25 items

5 min to complete

Higher T-score reflects greater symptomatology

Short-term visual working memory

Delayed Match to Sample test - Cambridge Neuropsychological Test Automated Battery (CANTAB) [95].

15 min to complete

Percent accuracy and mean reaction time for correct trials calculated.

Sleep (objective)

Actigraphy measure of sleep duration and quality. Children wore a ‘Motionlogger Micro watch’ (Ambulatory Monitoring, Inc., Ardsley, NY) on non-dominant wrist.

Seven consecutive days.

(1) Mean activity during sleep

(2) Minutes spent awake during the down period

(3) Sleep latency

(4) Sleep efficiency

(5) Wake after sleep onset

(6) Sleep fragmentation

Sleep (subjective)

(1) The Consensus Sleep Diary [96].

(2) Parent perceptions of sleep. Child’s Sleep Habits Questionnaire - Abbreviated (CSHQ-A) [97].

(3) Sleep Self-report (SSR) Questionnaire [98].

(1) Seven consecutive days.

Used to detect and remove artefacts in the actigraphy data.

(2) 22 items

High score indicates more disordered sleep

(3) 26 items (23 scored) High score indicates more disordered sleep

Gastrointestinal symptoms

The Gastrointestinal Symptom Rating Scale (GSRS) [99]— interview with child.

15 items

Higher scores indicate more severe symptoms.

Microbiome analysis

16s rRNA stool analysis using the Omnigene Gut OM-200 kit [100, 101] by Atlas Biomed [102].

Raw data analysed using the Deblur algorithm [103].

Read counts of microbial species, genera, and families calculated.

Estimation of alpha-diversity used Shannon [104] diversity metrics.