Can having adhd lower your iq test score?

Unless treated, yes: Untreated adhd can make it difficult to focus and concentrate on answering the questions on an iq test -- resulting in a lower score. Appropriate treatment should normalize this.

Dr. Pappas is right.: Scores on standardized tests of cognitive ability & achievement & daily academic performance can all be impacted negatively by clinically significant symptoms of inattention. Difficulty with Active Working Memory, retaining information long enough to use it, impacts math scores on timed tests to the extent that ADHD meds can improve both the # of problems completed & the # of correct answers.