A total of 111 unique effect sizes were derived from data representing 204,410 child measurement occasions; these studies included data from a total of 160,927 unique children.
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In childhood, parental use of spanking was associated with low moral internalization, aggression, antisocial behavior, externalizing behavior problems, internalizing behavior problems, mental health problems, negative parent–child relationships, im- paired cognitive ability, low self-esteem, and risk of physical abuse from parents. In adulthood, prior experiences of parental use of spanking were significantly associated with adult antisocial behavior, adult mental health problems, and with positive attitudes about spanking. The remaining four meta-analyses were not significantly different from zero. The 13 statistically significant mean effect sizes ranged in size from .15 to .64. The overall mean weighted effect size across all of the 111 study-level effect sizes was d .33, with a 95% confidence interval of .29 to .38; this mean effect was statistically different from zero, Z = 14.84, p = .001.