Corporal punishment makes children more aggressive and can harm them in the long term, says a study.

"Virtually without exception, these studies found that physical punishment was associated with higher levels of aggression against parents, siblings, peers and spouses," write study co-authors Joan Durrant and Ron Ensom.

Durant and Ensom from University of Manitoba and Children's Hospital of Eastern Ontario, respectively, based their findings on analysis of a number of researches over the past 20 years.

However, when parents in more than 500 families were trained to reduce their dependency on physical punishment, the difficult behaviours in the children also declined, the Canadian Medical Association Journal reports.

"Results consistently suggest that physical punishment has a direct causal effect on externalizing behaviour, whether through a reflexive response to pain, modeling or coercive family processes," write the study authors.  Physical punishment is also associated with a variety of mental health problems, such as depression, anxiety and use of drugs and alcohol, according to a Manitoba statement.

It may change areas in the brain linked to performance on IQ tests and increase vulnerability to drug or alcohol dependence, as recent neuroimaging studies suggest.

Attitudes toward the use of physical punishment have changed, and many countries have shifted focus to positive discipline of children and have legally abolished physical punishment.

Physicians can play an important role in advising parents on constructive approaches to discipline, based on evidence, to enhance children's healthy development.