I'm not good at reading medical studies, but this one seems relevant. There isn't a lot of study on the subject yet, but it looks like a little less than half of people with internet addiction also have personality disorders.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5370375/ Also, studies have shown that autistic people prefer interacting over text online to face to face interaction with others, which is a good thing for isolated and lonely individuals because it gives them some experience in social interaction that they can use to improve their real-life relationships with others. But this leaves them open for cyber bullying, manipulation and compulsive use of social media. A lot of prominent hackers are autistic because it feeds their need for attention, adulation, self-satisfaction and recognition. (These are the same needs that trolls and internet "experts" are looking to fill.) Low self esteem seems to be the cause.
https://www.autism.org.uk/advice-and-guidance/professional-practice/autism-internet This is a new area of research, so there isn't a lot of information on it.