(Medical Xpress) -- An accumulation of childhood adversities increases the likelihood that one becomes a bully, a new study found.
The adversities, however, do not have a significant effect on individuals being cruel to animals.
Researchers from the University of Michigan and four other universities reported that bullying and cruelty to animals are associated with various antisocial behaviors, such as getting into numerous physical altercations, having school attendance problems, lying and stealing.
For bullying, other triggers included being made to do chores that were too difficult or dangerous, threatening to hit or throw something. Significant factors related to animal cruelty involved swearing and saying hurtful things, having a parent or other adult living in the home who was incarcerated, and adult sexually assaulting.
"The cumulative burden of adversities had strong effects on the likelihood of bullying," said Brian Perron, an associate professor of social work at U-M. "The results also suggested that the mechanisms that give rise to bullying are separate from animal cruelty."
Perron's research focuses on issues related to the serious mental illnesses and substance use disorders.
The data came from the National Epidemiologic Survey on Alcohol and Related Conditions, which samples adults. The survey gathered information about substance use and psychiatric disorder from individuals living in households and group nationwide.
In the survey, 1,968 respondents indicated having a history of bullying and 475 had been cruel to animals. Nearly 32,000 people reported neither behavior, the research showed.
Persons reporting a lifetime history of bullying and cruelty to animals were significantly more likely to be men, single, have less education, and have lower levels of income. Compared with respondents ages 18 to 34, persons 35 and older were less likely to report bullying behavior and cruelty to animals.
In addition, persons diagnosed with lifetime alcohol or drug use were significantly more likely to report bullying and cruelty to animals than respondents without these disorders.
The findings appear in the Journal of Interpersonal Violence.
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