Normalization of increased retinal background noise after ADHD treatment: A neuronal correlate

Inattention, distractibility, and problems inhibiting irrelevant information impose a large disease burden in attention deficit hyperactivity disorder (ADHD). Problems with cognitive function are found in many major psychiatric disorders, and our understanding of ADHD might add to our knowledge of other neuropsychiatric disorders. Despite the high impact of ADHD, the pathophysiology and the mechanism of treatment action remains poorly understood. Increasing evidence suggests that elevated neuronal and retinal background noise plays a prominent role in ADHD. However, the effect of treatment (e.g., methylphenidate) on noise remains unclear. For this study, retinal background noise was assessed with the pattern-electroretinogram (PERG) in 20 drug-naïve adults with ADHD before and after treatment with methylphenidate and in 21 control subjects. Background noise was identified using the Fourier magnitude at frequencies adjacent to the stimulus-response frequency of 12.5 Hz. At baseline, we found an elevated retinal background noise in ADHD patients (Mdn = 0.079 μV) compared to controls (Mdn = 0.062 μV; z = -2.79, p = 0.016, r = -0.44). The noise in the ADHD group decreased significantly at follow-up after treatment with methylphenidate (Mdn = 0.069 μV, z = -2.39, p = 0.035, r = -0.39) while there was no change in the control group. PERG-based retinal noise is increased in adult ADHD and normalizes along with clinical symptoms following treatment with methylphenidate. The retinal noise level might be a promising marker of ADHD in clinical and basic research and illustrates the biological match with nonhuman ADHD models.