*3.2. ADHD Symptoms According to ARS*

The results of this study show that, under careful supervision, children can maintain a 4 weeks OD as documented in the nutrition and health diary. Reductions in ADHD symptoms of 40% or more were seen in 17 participants.

At T0, the 28 ARS parent ratings yielded M = 30.36 and SD = 8.87. Figure 2 shows the individual ARS total score trajectories from T0 to T2.

After 2 weeks (T1) of continuing usual nutrition behavior, parental ARS was not significantly different to T0 (T0: M = 30.36, SD = 8.87; T1: M = 29.54, SD = 9.64; *F*(1, 27) < 1).

From the 28 participants starting the diet, 26 (91.6%) completed. As shown in Figure 2A, after 4 weeks of OD (T2) we observed a significant reduction of ARS total score (T2: M = 15.62, SD = 8.05, *F*(1, 25) = 112.34, *p* < 0.0001). The percentage of improvement observed after the diet, according to the change in ARS total score, was 47.4% on average, ranging from 3.3% to 81.8%. Nine children showed at least 40% symptom reductions in both ARS subscales of inattention and hyperactivity/impulsivity. Thirteen children showed at least a 40% reduction in one subscale. Only three of the participants did not respond in either subscale.

According to Storebø et al. [27] a change of 6.6 points on the ARS is considered as the minimum for a clinically relevant difference. 22 of the 26 participants (84%) showed improvements of between 9 and 27 points between T1 and T2. Three of the 26 participants (11%) showed improvements of between 9 and 13 points between T0 and T1.

**Figure 2.** (**A**) Average changes in all participants (*n* = 28) of the ARS scores at each time point (means ± SD), *p* < 0.001 \*\*\* (ANOVA with repeated measurements). (**B**) ADHD Rating Scale total scale for all participants in the study. *n =* 28, T0: Baseline, T1: Start of the OD, T2: End of the OD.

#### *3.3. Identified Food Sensitivity*

The statistical analysis of the reintroduction phase showed 27 different types of food sensitivity (see Figure 3).

**Figure 3.** Identified food sensitivities during the study: Percentages of children (*n =* 16) reacting to the respective food with an increase in ADHD symptoms.

#### *3.4. Reactions to Intolerant Food after the OD*

Each responder to the OD showed individual food sensitivity, reacting to between 1–10 different foods in the food challenge phase. The three most common detected sensitivities are listed below as examples.
