The core of ADHD Imposter Syndrome lies in the state-dependent nature of executive function. In a neurotypical brain, executive function is relatively stable. If they can write a report today, they know they can write one tomorrow. In an ADHD brain, dopamine heavily dictates capability. If the task is novel or urgent, dopamine spikes, and the brain performs at an elite level. If the task is mundane, dopamine drops, and the brain is paralyzed.
When the ADHD person looks back at their "elite" performance, they objectively realize they cannot reliably replicate it on demand. The prefrontal cortex fails to integrate the "Hyperfocus Self" and the "Paralyzed Self" into one cohesive identity. The brain resolves this cognitive dissonance by deciding that the Paralyzed Self is the "true" identity, and the Hyperfocus Self was a temporary, frantic illusion.
Additionally, the working memory deficit prevents the ADHD brain from holding onto the emotional resonance of past successes. When facing a new challenge, the brain attempts to recall past victories to build confidence. Because the retrieval system is faulty, it draws a blank. Every new project feels like the very first time you have ever attempted the task, resetting your confidence to zero.
