The following article is on how happiness makes us less creative: Scientists explain how happiness makes us less creative.
The scientists here misunderstand the outcomes. Creativity is not stimulated from happiness or unhappiness but from emotion. The strongest emotion is manifest through the interaction that involves conflict. Therefore, the process involving conflict would, in rudimentary terms, be described as unhappy by study participants. But think of how brutal the conflict is within the particle interaction of nuclear fusion of the sun. Yet how much energy that produces. Same goes with creativity. That is the reason human DNA is set up for conflict while lower life forms are not.