Chemicals like this imho act like "global variables" for the neural network. Perhaps a bit like temperature in an LLM. They have an effect, but the effect is sort of holographic -- there's no way to predict/compute exactly what the effect will be, because it's a function of parameters that include all the training data, specifics of neuron function that depend on DNA and other environmental factors and so on. The effect might be beneficial, by some definition of beneficial, but it might not. Even a simple chemical like ethanol has a wide variety of effects on different people.