Prof. David Katz: Study Linking Circumcision to Autism ‘Far from Convincing’


Professor David Katz circumcision

A recent study of more than 340, 000 boys born between 1994 and 2003 in Denmark has concluded that circumcision raises the chances of an autism spectrum disorder before the age of 10 by 46 per cent, but if the circumcision was performed before the age of five it doubles the risk of developing autism.

The study shows how painful experiences in babies—both animal and human—have a long-term effect on pain perception.

Professor Morten Frisch of the Statens Serum Institut in Copenhagen, who led the research, stated: “Our investigation was prompted by the combination of recent animal findings linking a single painful injury to lifelong deficits in stress response and a study showing a strong, positive correlation between a country’s neonatal male circumcision rate and its prevalence of ASD in boys.”

But many doctors have expressed their doubts about the validity of the study.

Professor David Katz, Professor of Immunopathology at University College London and chairman Milah UK told the Daily Mail: “This report is far from convincing: correlation does not equal causation.”

Professor Katz added: “There is a long history of attempts to link autistic spectrum disorders to unrelated practices, such as the measles/mumps/rubella association, which proved to be fraudulent. There is general agreement that in people suffering from an ASD there are abnormalities that can be identified in brain structure and/or function.

“There is a strong genetic component, which may be a factor within the faith communities studied here, and which does not appear to have been explored amongst them. Some contemporary research does indicate that factors besides the genetic component are contributing to the increasing occurrence of ASD.

“For example, a variety of environmental toxins have been invoked to explain why these conditions are more prevalent today than they may have been in the past – but again proof of causation is lacking, and these factors are only likely to be relevant in those who are already vulnerable to them.”

Professor Jeremy Turk, Consultant Child & Adolescent Psychiatrist at Southwark Child & Adolescent Mental Health Neurodevelopmental Service, told the Daily Mail he was concerned with the reliability of the study.

“The findings of this research, while interesting, need to be considered carefully – one cannot draw very strong conclusions from the data, ” Professor Turk cautioned, pointing out: “This is not a causal study, but instead compares data sets and looks for correlations. While this is a valid way of doing a study, it means that we must be careful about any implications.”

Dr Rosa Hoekstra, lecturer in psychology at the Open University, told the Daily Mail: “I think this is an extremely speculative study. The study is purely based on register data and takes a registered autism diagnosis at face value, without considering cultural or social factors affecting the likelihood of an (early) autism diagnosis.”


  1. The papers are here:

    Bauer, Kriebel, 2013
    “For studies including boys born after 1995, there was a strong correlation between country-level (n = 9) autism/ASD prevalence in males and a country’s circumcision rate (r = 0.98). A very similar pattern was seen among U.S. states and when comparing the 3 main racial/ethnic groups in the U.S.”
    Frisch, Simonsen, 2015
    ” Results With a total of 4986 ASD cases, our study showed that regardless of cultural background circumcised boys were more likely than intact boys to develop ASD before age 10 years (HR = 1.46; 95% CI: 1.11–1.93). Risk was particularly high for infantile autism before age five years (HR = 2.06; 95% CI: 1.36–3.13). Circumcised boys in non-Muslim families were also more likely to develop hyperkinetic disorder (HR = 1.81; 95% CI: 1.11–2.96). Associations with asthma were consistently inconspicuous (HR = 0.96; 95% CI: 0.84–1.10).”

  2. The
    data behind this study makes sense but the premise that pain from circumcision
    causes the higher rates of autism does not. Specifically, pain does not cause
    autism, but pain relievers and particularly acetaminophen use is a risk factor associated with autism and this study provides more evidence of it. One of the characteristics of typical autism biochemistry is
    low levels of reduced glutathione in plasma. See: So it would make sense that substances that further exacerbate this
    biochemistry are dangerous to those with autism. Acetaminophen requires reduced
    glutathione to be metabolized and since the mid-1990s acetaminophen is given to many babies at the
    time they are circumcised. See this as one example: Therefore one would expect greater prevalence of autism in circumcised babies
    because of greater acetaminophen use, which is what this study shows.
    This is
    not the first time that circumcision has been associated with autism. See: In my view the authors of this earlier paper correctly attributed the cause to
    acetaminophen use. This previous study was using correlation across populations
    in aggregate though. The most recent study strengthens the case because it
    associates circumcision at the individual level with autism but as discussed
    this is almost certainly represents an underlying association of early
    acetaminophen use with autism.

  3. Thank you from the author of the first circumcision paper, you said
    it better than I could.  I want to add that we now have three high
    quality prospective cohort studies showing that prenatal acetaminophen
    use is associated with increased risk of adverse neurodevelopment- ADHD
    and autism phenotypes in 3 year olds.
    studies have investigated infant use, this current study adds to the
    body of evidence supporting the need for such investigation.


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