> The usual analogy is that you can always lower the IQ of a child by hitting them on the head with a hammer or by lacing their food with lead powder. But no intervention has been found that raises IQ.

Since almost no one, without deliberate intervention, experiences an environment completely free of known factors that are detrimental to IQ compared to the optimum environment, it's purely a semantic game to say that there are no known interventions that increase IQ.