If Mom Liked You Best, Everyone Loses Parents may not admit it, but picking favorites among their children is a fairly common practice. Now, new research reveals that this pattern -- known as differential parenting -- is not only detrimental to the child who receives the negative feedback, but also the entire family. Additionally, this new study shows that the more drastic the parenting styles between children, the worse the outcome of the mental health of all the children. "This was really surprising," said Jenny Jenkins, professor in the department of Applied Psychology and Human Development at the University of Toronto and lead author of the study. We expected differential parenting to operate stronger within the parent-child dynamic. However, differential parenting had a stronger effect on the entire family. "Differential parenting"-- giving mostly positive feedback to one child while mostly negative feedback to another -- has long been linked to negative effects for the targeted child. Until this study published Tuesday in the journal Child Development, however, its broader effects on the family as a whole had not been studied in detail. In her four-year longitudinal study, Jenkins observed the behavior of 400 Canadian families through direct in-home observation and self reports. She and her colleagues found that children in families affected by differential parenting showed higher incidence of problems with attention and social relationships. "Sibling divisiveness is a known result of differential parenting, with lasting effects into adolescence and adulthood," she said. In addition, researchers found that differential parenting was linked to other factors -- some of which were present in the home environment, and others that the parents had experienced in the past. Dr. Rahil Briggs, assistant professor of Pediatrics at the Albert Einstein College of Medicine in the Bronx, N.Y., said these factors stacked the deck against some parents. "While all parents know that it's best to avoid comparing siblings to each other, and to strive for equity in terms of attention, optimal parenting of this sort is incredibly difficult when faced with multiple risk factors, such as poverty, mental illness, and a history of adverse childhood experiences," said Briggs, who was not involved with the study. In short, mothers who were under emotional and financial stress had a harder time being fair to all of their children when parenting. "While none of this surprises me, it further supports the claim that we must support families, especially those families with young children, to help ameliorate some of these impacts of risk," said Briggs, who is also director of Montefiore Medical Center's Healthy Steps, a program aimed at getting parents and children off to a healthy start with the help of specialists in child development and behavior. The experiences of young children create a foundation upon which future development and behavior is built, and it's really imperative that this foundation be strong. While the study only shows an association between differential parenting and mental health outcomes for children in families -- not that one of these things necessarily causes the other -- it gives us very valuable information into family dynamics and the importance of parenting with fairness. "Parents don't set out to be horrible to one child versus another," Jenkins said. There are many environmental factors that lead parents to these actions. As parents, we have to be aware of these factors, and not let them affect our parenting.