Artificial Food Coloring Differentially Affects Alpha and Gamma Electroencephalography (EEG) Power in College Students with ADHD

Attention-Deficit Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder in children, and over half of these individuals carry the diagnosis into adulthood. Dietary exposure to artificial food coloring (AFC) has been reported to worsen symptoms of ADHD in children, but the validity of these findings has been debated. Furthermore, no studies have been completed to date examining the potential effects of AFC on young adults with ADHD. The current study examined the effects of AFC on brainwave activity of college students with and without ADHD. Participants (mean (SD) age of 20 (1.3) yrs) with (n=18) and without (n=41) ADHD completed baseline testing, including the Adult ADHD Self-Report Scale (ASRS) and 4 minutes of eyes-closed resting-state EEG. After avoiding AFC in the diet for 2 weeks, the ADHD group and 11 controls (referred to as Extended Controls or EC) were randomized to a double-blind placebo-controlled crossover challenge lasting three days each over two consecutive weeks. The challenge materials consisted of either 250 mg of combined AFC disguised in chocolate cookies or placebo chocolate cookies. The ASRS and EEG measures were collected at the end of each 3-day exposure. ASRS scores significantly differed at baseline between the ADHD and control group (p<0.001), confirming significantly elevated symptoms in the ADHD group. There were no differences between the ADHD and control group in any EEG frequency band at baseline. The ADHD group experienced a significant decrease in relative alpha power (p=0.04) and an increase in mean gamma power (p=0.05) in the posterior region (Pz, P3, P4, P7, P8, P9, P10, T7, T8, O1, O2) when challenged with AFC relative to placebo. There were no significant EEG changes in the EC group across challenge periods. Importantly, no changes were noted in ASRS scores across challenge periods in either group, but there was a marginally significant negative correlation between relative alpha power and the ASRS when exposed to AFC in the ADHD group (r= -0.49, p=0.06). These results indicate that AFC in the diet can change the brainwave activity of college students with ADHD, specifically in the mid and high frequency bands, but not in those without ADHD. More research is needed to better understand the underpinnings of how AFC changes brainwave activity, and if such changes are related to clinically meaningful symptom changes or more sensitive measures of attention not captured by the ASRS.