February 26, 2024

expert reaction to smoking/vaping and suicide attempts among children

A study published in JAMA Network Open looks at the use of tobacco products and suicide attempts among children.

Dr John Robins, Research Associate with the Nicotine Research Group at King’s College London, said:

“The study sets out to fill an important knowledge gap, i.e. ‘whether associations between smoking and suicidal behaviours, consistently observed among adolescents and adults who use combustible cigarettes, also manifest among preadolescent children, an increasing number of whom are exposed to emerging tobacco products’.

“However, the study does not seem to distinguish between smoked combustible cigarettes and other forms of nicotine/tobacco products.

“The authors say ‘our findings provide the first empirical evidence that an increased risk of SAs, consistently reported for cigarette smokers, extends to a range of emerging tobacco products and was observable among preadolescent children’ – yet they do not differentiate what type of products the children were using.  The authors do acknowledge this in their limitations: ‘given the young age of the study participants, the prevalence of the use of tobacco products was less than 2%, limiting the statistical power to perform fine-grained secondary analyses, such as investigating the effect of individual types of tobacco products…’.  But this is a pretty major limitation, and very much undermines the conclusion they draw about the risk associated with non-smoked tobacco products.

“Of the 101 children who were identified as using tobacco products at baseline, there were only 11 who were specifically identified as being e-cigarette users (and it appears these weren’t exclusive categories, so these 11 could also have been smoking cigarettes).  Likewise, none of the measures at 6- and 18-month follow-up appropriately differentiate smoked cigarettes and e-cigarettes.

“Whilst I completely agree with their call for ‘routine screening of the use of tobacco products among children and adolescents, especially when assessing suicide risk’, and their call for further research, their implication that the increased risk for suicide attempt can necessarily be implied to all types of nicotine containing product is flawed.”

Dr Rina Dutta, Reader in Suicidology and Psychiatry at King’s College London, said:

“This is interesting research, based on a cohort of almost 9,000 US youngsters aged 9-11 years at enrolment. The authors aimed to find out whether the use of any tobacco products (including e-cigarettes and vaping) was associated with an increased risk of self-injurious thoughts and behaviors (SITBs).  The K-SADS-5 (Kiddie Schedule for Affective Disorders and Schizophrenia for the DSM-5) contained the measures they used for non-suicidal self injury (NSSI), suicidal ideation (SI), and suicide attempts (SAs).  It is comprehensive, valid and frequently used in US studies.

“The reported results were based on cross-sectional analyses, and showed that lifetime use of tobacco products amongst the children when assessed at baseline, 6 months and 18 months were associated with both suicide attempts and suicidal ideation but not NNSI at baseline, year 1 and 2.  There was a 3 to 5 times increased risk of SAs.  The association remained, although somewhat weakened, even after the authors considered the effect of children’s thinking styles, temperament, and psychopathology outcomes.

“The authors themselves remark as a limitation that their study does not allow any conclusions about causality, just the association between youth tobacco use and suicidal attempts and ideation.  However, they were able to indicate there might be an association in timing, by studying youngsters who used tobacco products but did not report SAs at baseline and then later went on to have reported SAs by year 1 and year 2.  Although this analysis was based on small numbers.

“Whether smoking or vaping are modifiable risk factors that might be useful to address in suicide prevention efforts would require further evidence.  However, prevention and early intervention to reduce these behaviours has a real-world implication as they could improve the mental wellbeing of this vulnerable population group.”

Dr Sarah Jackson, Principal Research Fellow, UCL Tobacco and Alcohol Research Group, University College London, said:

“This observational study found that children who had ever used tobacco products were more likely to have made a suicide attempt than those who had never used tobacco products.  But an observational study like this tells us nothing about cause and effect.

“The authors conclude that ‘smoking tobacco products may be a modifiable risk factor for suicide’, which implies that one thing causes the other.  But as they state clearly in the paper, it’s impossible to know whether the association was causal.  Do tobacco products lead children to feel suicidal, or are children who feel suicidal more prone to use tobacco products, or are suicidality and use of tobacco products caused by another factor?  This paper simply cannot tell us.

“One thing we do already know is that smoking rates among adults with depression are substantially higher than among adults without depression.

“While the analyses accounted for some factors that might make a child more likely to try tobacco products and to feel suicidal (e.g., socioeconomic disadvantage and parental history of substance use and mental health problems), there are others that were not measured that could also explain this association (e.g. adverse childhood events).  In addition, is not clear from the paper which tobacco products children had used (e.g., cigarettes vs. e-cigarettes), how often they had been used, and whether those things affected the association with suicidality.”

Dr Adam Jacobs, Senior Director of Biostatistical Science, Premier Research, said:

“Although this paper found a statistically significant and clinically relevant association between use of tobacco products and suicide attempts in children aged 9-11, the observational nature of the study means that it cannot prove causality.

“Although the authors had made good attempts to control for confounding factors, it is impossible to control for all confounders precisely, especially when important confounders are personality traits, as seems probable in this case.

“While it is possible that use of tobacco products increases the risk for suicide attempts, it is also possible that some personality variables predispose to both suicide attempts and use of tobacco products.

“One feature of the analysis that makes a causal relationship seem less likely is that the authors also looked as suicidal ideation as an outcome, and found no significant effect of use of tobacco products on suicidal ideation after controlling for potentially confounding variables. If the relationship were causal, we might have expected a significant increase in suicidal ideation as well as suicide attempts.

“However, the lack of conclusivity of these findings should of course not be taken to mean that smoking in children is harmless. There are many other well established harms from smoking at any age, whether or not an increased risk of suicide is one of them.

“Although the paper emphasises that their definition of tobacco products includes vaping, the authors’ analysis did not examine smoking and vaping separately, but rather combined them together as simply ‘tobacco products’. This paper can therefore not tell us anything about whether any effect on suicidal behaviours, if it exists, is due to smoking, vaping, or both.”

Prof Marcus Munafo, Professor of Biological Psychology, University of Bristol, said:

“Disentangling cause and effect is notoriously difficult, and often statistical methods alone are inadequate. George Davey Smith demonstrated, many years ago, that there was an equally strong link between smoking and suicide, and smoking and homicide.  As George wrote, Unless the provisional wing of the health education lobby has moved on to a direct action phase, during which they shoot smokers, this association is very unlikely to be causal.

“In the absence of negative control outcomes like this, the results of this study should not be taken as strong evidence that vaping causes suicide.”

Prof Jamie Brown, Director of the Tobacco and Alcohol Research Group, and Professor of Behavioural Science, UCL, said:

“This is an important subject and the ABCD study is a significant international resource for investigating this topic. The major issue is the one that the authors acknowledge: these findings do not establish whether tobacco use causes suicide attempts.

“Although their analyses adjusted for a number of factors, there may well be unmeasured differences in the types of children who are both more likely to choose to use tobacco products and attempt suicide. The exposure included children who had only ever have used a product once or had only been exposed secondhand. If the size of associations persisted among this subgroup, then it would be more suggestive of unmeasured confounding because it would be somewhat biologically or psychologically implausible that such minor exposure could cause such a large increase in the likelihood of such a serious outcome.

“The authors were also unable to distinguish whether there were differences between different tobacco products, or whether any association was driven particularly by one product, such as cigarettes, which have been causally linked to worse mental health in a number of studies.”

Prof Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, said:

“Though this study seems to have been carried out generally competently in statistical terms, there are issues about the kind and amount of data that the researchers could collect that make its findings awkward to interpret. My own opinion is that it really doesn’t advance knowledge about tobacco use and suicidal behaviour, in children who were mostly not even old enough yet to be teenagers, to a helpful extent. (The children were nine or ten when they entered the study, and were followed up for two years.) The researchers end up proposing that more research needs to be done to clarify what’s going on. I’m glad that they didn’t go further than that and suggest any specific further actions, because I don’t think that the evidence from this study would support such suggestions.

“The researchers certainly aren’t saying that their work shows that smoking cigarettes, or vaping, by children aged nine or ten is going to cause them to be more likely to think about or attempt suicide – and it’s right that they don’t claim anything approaching this. I’ll explain why.

“One immediate issue is that this is an observational study. The researchers didn’t make any of the children use tobacco, or not use tobacco. Instead they asked them and their parents or carers questions about what they had done, in terms of tobacco use, suicidal thoughts or actions, and a great number of other things, and they made various measurements. They did indeed find that a bigger percentage of the children, who had used tobacco products, reported suicide attempts, than the corresponding percentage of children who had not used tobacco.

“But that doesn’t mean that the tobacco use necessarily caused this increased rate of suicide attempts. The children who did and did not use tobacco differed in many ways, in addition to the difference in tobacco use. Any of those other differences, or some combination of them, might be the actual cause of the difference in the rate of suicide attempts, and not the tobacco use at all. The researchers made statistical adjustments to allow for some of the other differences, but it’s never possible to adjust for everything that might be relevant. That’s why, in the research paper, the researchers say that “our observational study design precludes the determination of causal relationships”. They found an association, or they could have called it a correlation, and that simply can’t establish cause and effect.

“That can be said about any observational study, taken on its own. But this one has features that don’t arise in all observational studies, that make any discussion of cause and effect even more problematic.

“The study is, effectively, cross-sectional. That is, the two important measurements – whether children used tobacco, and whether they reported making a suicide attempt, were effectively made at the same time. In some observational studies that are interested in whether A could cause B, the measurements of B take place some time after the measurements of B. A study like that could show that B tends to happen after A. In that case, then at least the question of whether A causes B is still on the table. If B happened before A, then A couldn’t cause B. But that isn’t what sort of study was done here, not really. The researchers recorded both tobacco use and suicide attempts more than once during the two years of following up the children. But at each time point, they were recording whether the child had ever used tobacco, or had ever made a suicide attempt (or had suicidal thoughts, or harmed themselves physically without suicidal intent, which they were also interested in). The researchers seem not to have asked about exactly when these things occurred, if they did. So, in children who both used tobacco and made a suicide attempt, it remains possible that the suicide attempt could have occurred before the child ever used tobacco in which case the tobacco couldn’t be the cause of the suicide attempt.

“That leaves open the possibility of what’s called reverse causation – that is, that, to some extent anyway, it’s the suicide attempt that increases the risk that a child will later use tobacco, rather than the other way round. I’m not saying that this is the correct explanation – only that the study results don’t rule it out.

“Another possibility is that some other factor altogether – say some other aspect of the child’s psychological make-up – independently affects the chance that a child uses tobacco and the chance that they have suicidal thoughts or take suicidal actions. The researchers did investigate psychological factors, and they did find one (called negative urgency, a measure of one aspect of being impulsive) that was associated with suicide attempts, independently of tobacco use – but the issue of not being able to establish cause and effect applies here as well. The study can, at best, give some possible hints on what causes what, and can’t establish anything for sure.

“I’m certainly not saying here that the study rules out the possibility that using tobacco at these young ages causes an increased risk of suicide attempts. But that’s only one possible interpretation of the data that the researchers found. There are other possible explanations too, as I’ve described.

“But there’s something else that needs to be borne in mind. Yes, the researchers used data from nearly 9,000 children in all. But only 101 of them said they had ever used tobacco, or had tobacco use detected in a sample of their hair, when they entered the study, and at the latest follow-up that asked about this (18 months after entry), the number of users had gone up only to 151. That’s only about 1 in 60 of the children in the study. The great majority of the children being studied had not, ever, used tobacco products, which is what might be expected. And this would include children who had had a few drags on a cigarette once, or a few puffs of a vape, and never did it again. This small number of tobacco users is really the important number in determining what this study could detect in the way of correlations, rather than the total number of almost 9,000 participants.

“The research paper also tells us that, by the final follow-up, 321 of the children had reported a suicide attempt. That’s about 1 in 28 of them. Even though that’s not an immense risk, and even though attempts might not have been very serious, this is the figure in the paper that I personally find shocking – particularly if the sample of children for this research does represent the general picture in nine and ten year olds in the US. (The researchers do warn us that in fact the research participants might not in fact be typical of the US population.)

“However, neither the main research paper, nor the supplemental material to be published alongside it, tells us how many of the children who used tobacco at least once actually reported a suicide attempt. But it’s possible to do a back-of-the-envelope calculation that gives a rough idea of how many there were. I make it about 15 to 20 children, though there could have been rather more or fewer than that. So the finding of an association between tobacco use and attempting suicide does rather depend on these 15 to 20 or so children, who are not at all typical of the 9,000 who were studied. Also, even if it did turn out that it was tobacco use that caused the increase in the risk of suicide attempts – and that’s a big if – and even if we could eliminate all tobacco use in children of this age, that wouldn’t have done anything for the children who didn’t ever use tobacco but nevertheless carried out a suicide attempt. And there were probably over 300 of them.”

‘Use of Tobacco Products and Suicide Attempts Among Elementary School–Aged Children’ by Phil H. Lee et al. was published in JAMA Network Open at 4pm UK time on Monday 26 February 2024.

DOI: 10.1001/jamanetworkopen.2024.0376

Declared interests

Sarah Jackson: no interests

Jamie Brown has received unrestricted funding to study smoking cessation treatments from Pfizer and J&J, who manufacture medically licensed smoking cessation medications.

Adam Jacobs: No conflicts of interest to declare

Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee.  My quote above is in my capacity as an independent professional statistician.”

Marcus Munafo: no conflicts

John Robins: no CoIs

Rina Dutta: no CoIs to declare

No others received.