A study by a team around Dr Gregor Szycik from the Hannover Medical School in Germany analyzed possible long term effects of playing violent video games regarding the desensitization hypothesis (mainly based on observes short time effects).
The money quote of the paper is: “We interpret our results as evidence against the desensitization hypothesis and suggest that the impact of violent media on emotional processing may be rather acute and short-lived.”
The original paper: Gregor R. Szycik, Bahram Mohammadi, Thomas F. Münte and Bert T. te Wildt: Lack of Evidence That Neural Empathic Responses Are Blunted in Excessive Users of Violent Video Games: An fMRI Study
And an article on the topic: iflscience: Study Finds No Long-Term Effects Of Violent Video Games On Empathy
Image: By Nick Stirling - "IF 12: Cultivate"