Although it is an article about political hate (that the author classifies under 3 groups: Hot hate, Cool hate and Anonymous hate), it has an interesting paragraph about trolls, a topic that is often mentioned on this forum:

[...] consider a 2014 article in the academic journal Personality and Individual Differences, titled “Trolls Just Want to Have Fun.” Three Canadian psychologists found that habitual Internet commenting is strongly correlated with hateful personality pathologies. The total amount of time spent posting comments online correlated positively with sadism, psychopathy and Machiavellianism. And this held especially true for those who relished “trolling,” the anonymous posting of negative and destructive comments. The 5 percent of participants who listed trolling as their favorite activity earned the highest scores on those unsavory psychological measures.