In a surprising twist to the long-debated topic of video game violence, a recent study suggests that playing violent video games might actually decrease stress hormones in some players. Contrary to popular belief, the study found no increase in aggressive tendencies, indicating a more complex relationship between video game content and player responses than previously thought. The findings have been published in the scientific journal Physiology & Behavior.
For years, the impact of violent video games on behavior has been a contentious subject. Past research has often pointed towards a potential increase in aggression and stress among players of these games. This belief has fueled ongoing debates among parents, educators, and policymakers regarding the suitability of such games for young audiences. Motivated by these discussions and inconsistencies in previous findings, researchers embarked on a new study to explore the physiological and psychological effects of violent video games more comprehensively.
"In the non-violent condition, however, participants with higher scores in Machiavellianism had a higher increase in cortisol" - linked study
So people trying to be manipulative bastards in 'nice' games increase thier stress? Interesting.
Unfortunately the source study appears to be paywall and not yet on sci-hub, so don't know what specific games they used. As to how they define Machiavellianism, I assume something toke this:
"In the field of personality psychology, Machiavellianism is a personality trait characterized by interpersonal manipulation, indifference to morality, lack of empathy, and a strategic focus on self-interest." - Wikipedia
That's basically how I play every RPG... I don't care about the NPCs because they're not real, so everything I do is for the benefit of my character because that makes a tangible difference in the world (namely by giving me more money or power to better manipulate said world).