NIMH director: chemical imbalance notion antiquated

Via Critical Psychiatry comes this bit of news about NIMH director Thomas Insel claiming that mental illness is a "disruption in neural circuits" (despite admitting that they don't know how to define neural circuits). I don't buy this claim, at least in the form he makes it, but the strangest part comes in the conclusion:

While the neuroscience discoveries are coming fast and furious, one thing we can say already is that earlier notions of mental disorders as chemical imbalances or as social constructs are beginning to look antiquated.

Leaving aside the bit about social constructs - not sure what he even means by it - this is quite a statement from the head of NIMH. So he's acknowledging that the host of drugs whose supposed mechanism of action is altering chemical "balances" don't in fact have a scientific basis? This is indeed what the research has long shown, but it's striking to see it acknowledged so casually and for this not to be news.