Children who are smacked are more likely than those who are not to become aggressive and anxious, no matter what the cultural norm, a study says.
Researchers interviewed families in six countries
A global research team studied 336 families across six countries - some of which accepted smacking as legitimate discipline and some which did not.
It found smacking resulted in more behavioural problems in all countries.
But in countries where smacking was the norm, the problems were less acute, the Child Development journal reported.
Researchers from universities in Europe, Asia and the US carried out the study.
There are mixed opinions over whether smacking leads to behavioural problems and whether the society the child is being brought up in has an impact.
Some countries across Europe have outlawed smacking, but globally most do not have regulations.
In England and Wales, smacking which leaves more than a transient mark was banned earlier this year, although "reasonable chastisement" is allowed.
Mothers and children from China, India, Italy, Kenya, the Philippines and Thailand were all interviewed.
The mothers were asked how often they physically disciplined their children, and how often they thought parents in their country resorted to smacking.
Then they interviewed the mother and child about the child's emotional state and how often they got into fights.
Mothers in Thailand were least likely to physically discipline their children, while those in India and Kenya were the most likely.
All the children who were disciplined showed higher levels of aggression, anxiety and other emotional problems than their contemporaries.
But researchers did find that in countries where physical discipline was more common and culturally accepted, the behavioural problems were not as bad as when it was carried out where it was more taboo.
Lead researcher Jennifer Lansford said the findings prompted the question of whether physical discipline was "acceptable, regardless of whether it occurs commonly within a cultural group".
But she added: "One implication of our findings is the need for caution in making recommendations about parenting practices across different cultural groups."
Paul Farmer, chairman of the Mental Health Alliance, which represents professionals and charities, said environmental factors such as physical discipline were likely to have an impact on behavioural problems no matter what the cultural norm.
But he added: "It is not just anxiety and aggression that can be caused by trauma. Other emotional problems, such as depression, can result."
Mary Marsh, director of child protection charity NSPCC, urged parents not to smack their children.
"A child's safety and respect for their human rights should be at the core of caring for children."
And she said parents needed support in finding out about positive parenting and alternatives to hitting.
Researchers from Duke University and the University of Oregon, both in the US, the Chinese University of Hong Kong, Goteborg University in Sweden, Naples University, the University of Rome, Chiang Mai University in Thailand, and Delhi University in India, took part in the study.