‘Smacking increases cancer risk’, the Daily Express boldly reports, while The Sun believes that smacking can also increase the risk of asthma or heart disease. These reports exaggerate a piece of research that has significant limitations.
The news is based on a study that asked a sample of Saudi Arabian adults with cancer, asthma or heart disease how frequently they had been physically punished or verbally insulted as a child (referred to in the papers as smacking and shouting).
The researchers then looked at whether there was a link between the two, comparing these adults with healthy controls. They found that reported physical punishment and insult was associated with an increased risk of developing adult cancer, asthma and heart disease.
The researchers speculate that regular beatings and insults create a sense of threat in a child and this may then trigger stress responses that may have long-term biological consequences.
Despite the interesting nature of this study, it is subject to a number of significant limitations, such as:
- self-reported information
- the cultural differences between Saudi Arabia and Western countries may mean that the results are not applicable here (the researchers say beating is legal and more culturally acceptable in Saudi Arabia)
There are likely to be extensive confounding factors associated with the likelihood of being physically punished as a child and risk of later disease which the study has not taken into account.
Overall, this study does not provide conclusive evidence that smacking directly causes chronic diseases such as cancer.
Where did the story come from?
The study was carried out by researchers from the University of Plymouth in Devon. Sources of funding were not reported. The study was published in the peer-reviewed Journal of Behavioural Medicine.
The story was picked up by the Daily Express, Daily Mail and other media, the findings were exaggerated and the headlines misleading. The media reports did not take into account the important limitations of this study.
What kind of research was this?
This was a cross-sectional study of Saudi Arabian adults diagnosed with either cancer, asthma, or cardiac disease, and a group of healthy controls. The researchers asked the participants about the physical punishments and verbal insults from parents that they had experienced as a child, to see whether there was any relationship between this and their diseases in adulthood. As childhood punishments are likely to have occurred before adult disease development it would, in theory, be possible to establish a cause and effect association.
However, the most important limitation in this study is that any association seen between the two is likely to be influenced by extensive confounding factors (socioeconomic, environmental and lifestyle factors) which this study has not been able to take into account.
An issue as complex as the effects of parenting on the health outcomes of a child is likely to be subject to a wide range of confounding factors. For example, children who were often smacked for perceived naughty behaviour may have had poor impulse control that could have persisted into adulthood, leading them into behaviours that have adverse effects on their health, such as smoking.
However, based on the limited data provided in the study it is impossible to confirm any theories that the findings may suggest.
According to the researchers, physical punishment is illegal in 24 countries either at school or in the child’s home and in 94 countries (including the UK) it is illegal in school but ‘reasonable’ physical punishment is permitted by parents.
The researchers report that in the US and some countries in the Middle East and Asia, physical punishment is legal in school and in the home. They say that the use of beating and insults is an acceptable parenting style in Saudi Arabia, where this study took place. The researchers report that in Saudi Arabia, physical punishment in schools was banned in 1996, but that physical punishment remains legal in the home. The UK has stopped short of an outright ban on smacking, allowing parents to physically chastise their children without causing “reddening of the skin”.
The authors report that no other studies have examined the effects of physical punishment on adult physical health. It is very difficult to apply the findings of this study in Saudi Arabia to other countries with social and cultural differences.
What did the research involve?
The researchers examined 700 adults aged between 40 and 60 years who were all citizens of Saudi Arabia. This group of 700 people was made up of:
- 150 people with diagnosed cancer (75 male, 75 female)
- 150 people with diagnosed asthma (75 male, 75 female)
- 150 people with diagnosed heart disease (75 male, 75 female)
- 250 healthy people without diagnosed disease, recruited from administrators and nurses working at three hospitals (the researchers considered this group to be the controls)
The authors report that all participants would have been children at the time when physical punishment was still permitted in schools.
To assess the frequency of punishment as a child, all participants were asked: “Were you beaten as a child?”. Participants responded on an eight-point scale ranging from ‘never’ to ‘at least once a day’.
To assess the frequency of insults as a child, participants were asked: “Did your parents verbally insult you?”, with the same response scale used.
Punishment and insult reported as monthly or more frequent was considered ‘frequent punishment’.
The participants were also asked about their own education and the education of their mother and father, based on a seven-point scale ranging from ‘none’ to ‘intermediate’ and ‘higher graduate’.
The researchers considered that physical punishment may cause a physiological threat response which creates stress in young children.
They made the assumption that physical punishment is likely to be combined with other aspects of parenting that also signals threat and creates stress.
The implication of this would be that prolonged feelings of stress have harmful biological effects that can affect adult health.
What were the basic results?
Overall, 32.3% of the participants reported being beaten by their parents at least once a month or more and 46.6% reported being verbally insulted once a month or more. Infrequently punished participants were significantly younger, more educated and had parents who were more educated.
Following adjustments to match the participants on these demographic details, more frequent beatings were associated with a significantly increased risk for:
- cancer (median relative risk [RR] 1.69)
- heart disease (median RR 1.37)
- asthma (median RR 1.64)
More frequent verbal insults were associated with a significantly increased risk for:
- cancer (median RR 2.09)
- heart disease (median RR 1.57)
- asthma (median RR 1.88)
There was some evidence of an increased risk of cancer and asthma when beating was reported with a frequency of once every six months.
How did the researchers interpret the results?
The researchers conclude that Saudi Arabian adults who reported being beaten or insulted as a child were more likely to have cancer, cardiac disease and asthma when compared to a group of healthy individuals. They say that these results suggest that a threatening parenting style is associated with an increased risk for these diseases in later life. They suggest it is not the physical punishment itself, but the threat response produced by use of the physical punishment, that leads to these negative outcomes.
Lead researcher, Professor Michael Hyland, is quoted as saying, ‘Early-life stress in the form of trauma and abuse is known to create long-term changes that predispose to later disease.’
In discussing the study’s findings he said, 'This study shows that in a society where corporal punishment is considered normal, the use of corporal punishment is sufficiently stressful to have the same kinds of long-term impact as abuse and trauma.'
He added, ‘Our research adds a new perspective on the increasing evidence that the use of corporal punishment can contribute to childhood stress, and when it becomes a stressor, corporal punishment contributes to poor outcomes both for the individual concerned and for society.'
This study provides limited evidence of a direct link between physical punishment and insult and the development of cancer, asthma or cardiac disease in adult life. It does not provide any evidence that one causes the other.
There are important limitations to this study, including:
- While the researchers have taken into account age and education, there are likely to be extensive confounding factors that are associated with both the likelihood of the individual being punished as a child and their likelihood of later life disease. These include socioeconomic, environmental and lifestyle factors which may have an influence on both the parents and the child, and which continue to influence the child as they grow into adulthood (such as poorer diet).
- Participants were asked to recall events that took place in their childhood. This also may affect the results as it relies purely on the memory of the adult.
- Also, it is possible the adults did not correctly report whether they were punished or insulted or not – for example, what one adult considered to be a verbal insult, another adult may have not thought of as being the same.
- The authors suggest that better understanding of children’s perceptions of punishment may show when punishment is and isn’t considered stressful.
- Though the overall sample size was quite large, at 700, numbers in each disease group, at 150, were actually too small to draw reliable conclusions.
- There may be important social and cultural differences between Saudi Arabia and other countries which mean these results cannot be easily generalised to other countries.
In conclusion, the headline that ‘smacking increases cancer risk’ is misleading as it does not take into account the limitations of the study.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Sun, 12 November 2012
The Mirror, 12 November 2012
Daily Mail, 12 November 2012
The Daily Telegraph, 12 November 2012
Daily Express, 12 November 2012
Links to the science
Journal of Behavioural Medicine. Published online September 29 2012