He then plotted the course of mood against creative production. The resulting curves are striking: he found a consistent link between the intensity of negative emotions, especially sadness, and subsequent periods of artistic brilliance. He concluded that such sadness was not just correlated with creativity but that it actually had a reliable causal effect, typically delayed by some months.

— The Matter With Things: Our Brains, Our Delusions and the Unmaking of the World by Iain McGilchrist a.co/h521vtL