Physical Punishment and Mental Disorders

I do not care for statistics.  It's not in my DNA to ENJOY them but this is the perfect example why all pharmacists (and the lay public, for that matter) should understand and interpret study results.  Just the other night, I was watching the news and the anchor states, "Parents should think twice about spanking their children."  Most people would look at the anchor, hear the words, and then turn right around and pass it on as though it was spoken by God Himself. A study was cited:

BACKGROUND: The use of physical punishment is controversial. Few studies have examined the relationship between physical punishment and a wide range of mental disorders in a nationally representative sample. The current research investigated the possible link between harsh physical punishment (ie, pushing, grabbing, shoving, slapping, hitting) in the absence of more severe child maltreatment (ie, physical abuse, sexual abuse, emotional abuse, physical neglect, emotional neglect, exposure to intimate partner violence) and Axis I and II mental disorders.

METHODS: Data were from the National Epidemiologic Survey on Alcohol and Related Conditions collected between 2004 and 2005 (N = 34 653). The survey was conducted with a representative US adult population sample (aged ≥20 years). Statistical methods included logistic regression models and population-attributable fractions.

This is a retrospective study which automatically introduces bias.  Correlation does not imply causation.  That's the biggest issue I see with this study.  For example, the media will pick up a press release about this type of study and report that spankings make children grow into adults with mental disorders, but correlation does not imply causation.  For example, children who were spanked may end up with a mental disorder, but there is no proof that it was the spanking itself that caused the mental illness but perhaps several other factors or combinations of factors.  Even schizophrenia and depression have had genetic components.  What happened to pure genetics?

The next big issue with this study is they looked at many types of mental illnesses since it is not very efficient to run a large study, gather data, and analyze it to look at only one type of mental illness.  Scientific studies, however, rely on statistical analysis to determine whether something is true.  Even if your estimated error is less than one percent, in a study examining thousands of items some will appear to have an effect even though they are just statistical aberrations.  These false positives are then reported, and when a new study fails to confirm them as true, the press reports a scientific “change of mind”.

Finally, when a cohort study is retrospective, the problem is compounded since retrospective studies often rely on memory.  If you developed a mental illness, you may have a different memory recall of punishment and its effect and your perception vs if you did not have a mental disorder.

Be careful with retrospective studies!   As in this case, there are many flaws and biased automatically introduced.

I definitely understand the rationale for wanting to run this study as many parents are probably over the top with physical punishment; however, I don't believe those parents that reserve a spanking for a type of punishment as abusive or that their child will end up with a mental illness due to that one decision.  Too bad the media doesn't know how to interpret studies!

Another critique:

While the new study rules out the most severe cases of physically lashing out at children, "it does nothing to move beyond correlations to figure out what is actually causing the mental health problems," says psychologist Robert Larzelere of Oklahoma State University,. He criticized the study's reliance on memories of events from years earlier, and says it's not clear when punishment occurred.

Afifi acknowledges that it's difficult to change people's mind on this topic, but says "we're confident of the reliability of our data, and the data strongly indicate that physical punishment should not be used on children — at any age. And it's important for parents to be aware of that."