Sorry, no, it is nowhere near a testable scientific hypothesis. Perhaps you mean "hypothesis" (And Rose, above, "theory") loosely in the vernacular, but these are technical terms in science as well.

ADs shut down reactive response mechanisms, classically by keeping more serotonin in the synapses. It's analogous to a painkiller shutting down pain signals. Some people like this squelching of irritating reactivity, while some people feel it erased part of their personality and identity. Other ADs have an amphetamine component, giving some people motivation to round out the flatness. There is a basic understanding that neurotransmitters and synapses are being targeted by the chemicals, but this is hardly a theory of the brain. It's clinical trial and error for the most part. It's a clinical approach.

I wish people would stop throwing around high-powered scientific terms, because it just confuses people who have a tendency to then become dogmatic. I admit this is a pet peeve because I know someone who believes in The Secret, and argues for it based on a "scientist" who supports it (trained in social science, actually) without having a single clue what any actual science is about.