Adolescent cannabis use and educational attainment: a causal relationship?

Maria Melchior, Laura Pryor and Marie Jauffret-Roustide


Our study, recently published in the IJE, shows that youths who initiate cannabis use before the age of 17 years are 60% less likely to pursue higher education than those who never used cannabis. An original aspect of our study, which was based on data from the longitudinal TEMPO cohort in France, is that we were able to take into account youths’ psychological and school difficulties in childhood and adolescence, as well as their parents’ characteristics.

In recent decades, cannabis use has become frequent among youths growing up in Europe, North America and Australasia. The potential health effects of cannabis use include reductions in memory and concentration. Because the brain is thought to develop until the age of 25, adolescent substance use could have lasting negative effects on executive functions, which can in turn result in school difficulties and low educational achievement.

Continue reading “Adolescent cannabis use and educational attainment: a causal relationship?”

Spatial quantification of the world population potentially exposed to Zika virus: how many people are in danger?

Alberto J. Alaniz, Antonella Bacigalupo and Pedro E. Cattan


Our study, published recently in the IJE, shows that 43.9% of the world population — about three billion people — are exposed to Zika virus, due to the probability of presence of its vector: the mosquito Aedes aegypti.

Zika virus has become an important public health problem worldwide. In 2016, the World Health Organization released a global alert in response to the risk of this virus to the population. The pathogen is especially aggressive in pregnant women, because it has been associated with microcephaly in the fetus. On the other hand, it causes different clinical manifestations in adults, such as mild fever, rash, headache and joint pain. In some countries the alert was very restrictive, even going so far as to contemplate birth control programs to avoid the infection of pregnant women.

Continue reading “Spatial quantification of the world population potentially exposed to Zika virus: how many people are in danger?”

Causality in Epidemiology – Themed issue

jane-ferrieJane E Ferrie

Arguments about causal inference in ‘modern epidemiology’ revolve around the ways in which causes can and should be defined. The potential outcomes approach, a formalized kind of counterfactual reasoning, often aided by directed acyclic graphs (DAGs), can be seen as too rigid and too far removed from many of the complex ‘dirty’ problems of social epidemiology, such as social inequalities and racism. If a potential ‘cause’ cannot be manipulated is it sensible to disregard it, relegating it to the ‘not suitable for epidemiology’ category? The use of properly constructed DAGs may aid causal thinking and help plan relevant analyses – Neil Pearce and Debbie Lawlor provide a simple, but excellent discussion of the use of DAGs in their essay review of Causal Inference in Statistics: A Primer by Judea Pearl and colleagues. However, increasingly, DAGs and analyses are constructed by computer programs, such as DAGitty, now available as an R package ‘dagitty’. Useful as such programmes are, the temptation to use evaluations of DAG-dataset inconsistency to generate purely data-driven, post-hoc modifications to DAGs, raises concern about overfitting and biased inference. Continue reading “Causality in Epidemiology – Themed issue”

Exposure to physical assault is associated with premature mortality in Russian men


Vishal Bhavsar

Our study, published recently in the IJE, looks at the relationship between experience of violence, in the form of physical assault in the previous 12 months, and premature mortality in a sample of working-age Russian men living in Izhevsk in the Southern Urals.

We did this study because, although violence is considered important at a policy and political level, empirical public health research on the subject is patchy. There has been quite a lot of research on the relationship between violence exposure and later mental health problems, particularly post-traumatic stress disorder, and more generally the impact of violence on coping and psychological characteristics, particularly in children. Recently, there has been considerable work on the descriptive epidemiology of violence against women, both from a general population perspective and in studies focusing on women with serious mental illness.

In contrast, we found that population-based research on the physical health effects of exposure to violence was limited, and we decided to focus on possible associations between assault and mortality in our study.

Continue reading “Exposure to physical assault is associated with premature mortality in Russian men”

Metabolic Phenotyping in Epidemiology

g-mak-talisker-jan-2016-bristol-wwwMika Ala-Korpela and George Davey Smith

Metabolic phenotyping, nowadays most often termed metabolomics, is becoming increasingly applied in epidemiology. Recent technological developments, driven by mass spectrometry and nuclear magnetic resonance spectroscopy, have recently resulted in increasing numbers of quantitative molecular applications at an epidemiological scale. The results suggest that these kinds of new technologies are inevitably becoming common in research projects aiming for molecular understanding of metabolic health and diseases. It is also evident from the epidemiological applications that absolute quantification of identified molecular entities is the very key for biomedical applications, not to mention potential clinical translation of metabolomics methodologies and findings. Continue reading “Metabolic Phenotyping in Epidemiology”

Evolution or revolution? The health of New Yorkers under Mayor Bloomberg

Peter Muenning, Daniel Vail and Ryan K. Masters

hss_cohort9-ryan-mastersdaniel121757476_title0hWhen Michael Bloomberg was elected Mayor of New York City (NYC), he set forth an ambitious agenda to efficiently sync municipal agencies. Improving New Yorkers’ health was part of his motivation. For example, expanding parks and bike lanes would not only improve people’s quality of life and expand transportation options, their presence would also encourage healthy behaviours. So, why not create cross-agency agendas that allow parks with bike lanes to be created on city streets? Innovative thinkers were hired and were given an unusual amount of political capital and logistical support to implement their plans.

Sadly, very little was done to actually evaluate the programs that were implemented. When the Bloomberg administration promoted the idea that life expectancy had greatly increased as a result of its coordinated policymaking, some people scratched their heads. Sam Preston and Irma Elo argued that improvements in life expectancy in NYC could be explained by a large inflow of healthy foreign migrants. They made this argument by eloquently showing the influence that immigrants had on the city’s life expectancy.
Continue reading “Evolution or revolution? The health of New Yorkers under Mayor Bloomberg”

Marking World AIDS Day 2016


World AIDS Day is held on 1 December every year and provides an opportunity for people across the globe to show solidarity with the millions of people living with HIV. This year’s campaign theme is ‘HIV Stigma: Not Retro, Just Wrong’ #HIVNotRetro and you can find out more about how to get involved at

Image credit: Support for International AIDS Memorial Day by Sham Hardy, CC BY SA 2.0

To mark World AIDS Day 2016 we are sharing an extract from Fighting the stigma of HIV and AIDS published on the OUP blog and co-authored by Landon Myer, a member of the IJE Editorial Board. The articles he references have been made freely available until 1 March 2017. Continue reading “Marking World AIDS Day 2016”

New evidence that maternal micronutrient status modifies the effect of neonatal vitamin A supplementation

headshotEmily Rose Smith

Although the World Health Organization (WHO) recommends vitamin A supplementation for infants and preschool children aged 6 to 59 months to reduce morbidity and mortality, the debate about whether or not to supplement newborns has been controversial.  (Note that an exchange in IJE 44:1 in 2015 also demonstrated some controversy about whether or not to continue supplementation for preschool-aged children). In an attempt to inform global policy, three large clinical trials were conducted in Tanzania, Ghana, and India. However, these trials found conflicting results. The trial conducted in India—consistent with previous trials in the region—found that supplementation reduced the risk of infant death, while the other two trials in Ghana and Tanzania found no effect of supplementation.

Inconsistency between the trials might indicate that some, but not all, children benefit from neonatal vitamin A supplementation (NVAS). Our study, published in the IJE, examines data from the Neovita trial in Tanzania, the largest NVAS study ever conducted in sub-Saharan Africa. We looked to see if there were any subgroups of infants in this trial who benefited from supplementation. Continue reading “New evidence that maternal micronutrient status modifies the effect of neonatal vitamin A supplementation”

Smoke exposure in early life and Rheumatic Heart Disease

david-phillipsDavid Phillips

Rheumatic Heart Disease (RHD) is caused by a bacterial (streptococcal) throat infection acquired in childhood.  Although this type of infection is common and widespread, a small proportion of children so affected go on to develop an inflammatory condition that leads to scarring and narrowing of the heart valves and, in time, heart failure. Early on in the course of the disease the joints may be affected – hence the term “rheumatic”.

Still an important disease
At one time Rheumatic Heart Disease was common throughout the UK, Europe and the US; it was the most important cause of heart disease among young adults in Victorian Britain and probably caused the death of Mozart.  Although rare now in most developed countries, it remains an important public health problem in many low and middle income countries. The disease is widespread in the Middle East and Asia, and the the poor indigenous populations of some wealthy countries, for example among Australian Aboriginees and New Zealand Maoris. It is particularly prevalent in sub-Saharan Africa, where it is one of the commonest causes of heart disease, typically affecting children or young adults. There it carries a grim prognosis because of the lack of specialised treatment. Continue reading “Smoke exposure in early life and Rheumatic Heart Disease”

Last but not least – the 2016 IJE conference

photoLuisa Zuccolo

The IJE conference took place in Bristol on 7 October  2016, a one-day, one-off event.

Rodolfo Saracci, as ever bow-tied and in good spirits, did the honours throughout the day. It was under his IEA presidency that Shah Ebrahim and George Davey Smith were hired as IJE editors, and Rodolfo praised their editorial work by likening it to conducting research (“exciting, adventurous, challenging”), and acknowledging that brave decisions have exposed them to the future judgement of historians.

A historical perspective was also taken by Tom Koch, who recalled the very origins of the IJE, of epidemiology itself, and of the transition to modern epidemiology, and by Alex Mold, who told us about the historical relationship between the public and public health by drawing on three key epidemiological narratives (John Snow and the pump’s handle, Richard Doll and the British Doctors’ study, Jerry Morris and London’s bus drivers and conductors). Continue reading “Last but not least – the 2016 IJE conference”