If yawning is associated with the first derivative of dopamine levels, then you'd think taking a higher dose of Adderall than prescribed would make one immediately yawn. People who have been prescribed Adderall (specifically non-time-release L-Amphetamine): does this happen?

(Or, equivalently, the same question to anyone without ADHD who has taken Adderall, or anyone who has taken meth or snorted cocaine. But these are likely to be less common experiences in this community.)