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An observational study published in The British Journal of Psychiatry looks at life expectancy of adults diagnosed with ADHD.
Prof Kevin McConway, Emeritus Professor of Applied Statistics, Open University, said:
“This is a striking study, though inevitably it leaves many important questions unanswered. It provides, fairly directly, an estimate of by how much the lives of UK adults diagnosed with ADHD are shortened, on average, compared to adults without that diagnosis. It’s the first study to make this estimation in a UK population, and it seems to be the first to do it anywhere, apart from one previous study that used US data and very different statistical methods.
“Even allowing for some statistical uncertainty, the estimated differences in life expectancy between people diagnosed and not diagnosed with ADHD are rather large. But really the important question that follows is, what can be done about this? That depends on whether the reductions in average life expectancy are caused (somehow) by ADHD, and if they are, how they are caused.
“This is observational data, so there are inevitably some doubts about what is causing what. In the view of the researchers, based partly on findings from this study but mostly on other research and their experience, the differences in life expectancy arise because people diagnosed with ADHD do not receive adequate treatment, for the ADHD itself and for other mental and physical health conditions that are more common in people with ADHD.
“But the web of potentially interacting factors that might be involved is certain to be complicated.
“There may be some factors that arise before birth or in very early life that could separately affect the chance that a person is later diagnosed with ADHD, and the chance that they die at a younger age than average. Those could be genetic, but there are other possibilities that could well be more important.
“For instance, the researchers report that they could not take people’s ethnicity into account in their calculations, because they did not have enough useable data on it. It’s well known that people from several minority ethnic groups have worse health than average in various ways. This is largely due, it is thought, to social and other disadvantages that affect people in these groups (and not to genetic differences).
“Perhaps if these researchers had had good data on ethnicity, and if a person’s ethnic background was somehow separately related to their chance of being diagnosed with ADHD, the estimates of the reductions in life expectancy would be different – though I’d certainly be very surprised if the reductions disappeared entirely.
“But that couldn’t be done here. Possibly there are other factors arising before birth or in very early life that could be involved in a similar way.
“The researchers did take account of people’s age, sex, and a broad measure of where they lived (by matching the non-ADHD controls with people diagnosed with ADHD by age, sex and the GP practice where they were registered). But they did not control statistically for any other factors.
“It’s interesting to consider why the researchers decided not to make statistical adjustments for deprivation, because the researchers write about their reasons. They had access to a deprivation measure (the Townsend quintile, based on 2001 Census data), for about four fifths of the participants, and that could have been used. The 2001 Townsend quintile isn’t an ideal deprivation score, but it is arguably better than nothing.
“But the researchers chose not to use the score for adjustment, arguing that having ADHD probably leads to a greater chance of living in a more deprived area, and that living in a more deprived area is in turn (from other research) known to be associated with a shorter life expectancy.
“So the appropriate action, if this argument is correct, could be to examine whether providing better services for people with ADHD might make it less likely that they would live in deprived areas. (And to continue to work on trying to change the association between deprivation and poor health, for all people, and on improving conditions in areas now considered deprived.) Showing results adjusted for deprivation could make it less clear that such actions are appropriate – if the researchers’ argument about how deprivation comes into the picture are correct.
“The point is that, according to the researchers’ argument, deprivation lies on a path of cause and effect going from having ADHD to having a lower life expectancy, and adjusting for deprivation could disguise that ADHD and life expectancy are associated. The data from this study do not show that this is the case, but it is certainly plausible.
“They also didn’t make statistical adjustments for differences between the people diagnosed with ADHD, and those with no diagnosis, in a list of other physical and mental health conditions, in whether they smoked, and in whether they used alcohol in a potentially harmful way, even though they had data indicating that potentially harmful health conditions, and smoking and problematic drinking, were more common in people with ADHD.
“This may look odd, given the statistical efforts that researchers typically make to adjust for factors in observational studies, in order to be comparing like with like as far as possible. But in my opinion, not making these adjustments makes sense here, even though it might have been interesting to see adjusted figures too.
“Things like differences in smoking, alcohol use, and several health conditions are likely to be consequences of the ADHD, to a large extent, and so be some of the reasons that having ADHD leads to a shorter life (on average), rather than being independently associated with an ADHD diagnosis and with death rates. That is, they potentially explain the manner in which ADHD affects death rates, rather than being potential reasons why the observed association between ADHD and death rates is not one of cause and effect. Plausibly, they lie on a path of cause and effect that goes from ADHD, through these factors (and others), to death rates – but data from this analysis can’t indicate whether this is actually the position.
“So these are factors that need to be considered in deciding on actions to be taken to reduce the shortening in life that is associated with being diagnosed with ADHD. Presenting results after adjustment by these factors might hide the overall issue, rather than clarifying it. More research on how all the various factors are interrelated would be useful, but in my view that shouldn’t prevent work on improving services for people with ADHD.”
Prof Philip Asherson, Professor of Molecular Psychiatry, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, said:
“This is an excellent and well conducted study that highlights the impact of higher mortality rates in ADHD on shorter life expectancy. The precise causes of early death are not yet confirmed, but we know that ADHD is associated with higher rates of smoking, obesity, cardiovascular disease and cancer among other health problems. Adults with ADHD are more likely to engage in unhealthy habits such as binge eating or smoking, and risk-taking behavior. There may also be biological links with autoimmune and other physical health disorders. ADHD is increasingly recognised as a serious condition in adults associated with poor health outcomes. Services to support adults with ADHD and improve both physical and mental health outcomes lag behind those for other common conditions such as anxiety, depression, hypertension and obesity. Of particular concern are limited access to diagnosis and treatment including psychosocial support. Until this is addressed the shorter life expectancy demonstrated in this study is likely to continue.”
Prof Oliver Howes, Professor of Molecular Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, KCL, said:
“The main finding of this study that people with ADHD die sooner than people without ADHD shows the massive impact of ADHD on people’s lives. The study is also striking in showing how few people with ADHD get a diagnosis. These findings highlight the need for much more investment in mental health services so people can get the help they need. The study adds to lots of other evidence that people with other mental illnesses die sooner than people without mental illness to show this for ADHD as well. Strengths of the study include that it was based on a large UK database. Some limitations include that they were not able to look at when ADHD was diagnosed in relation to other medical problems, or the impact of treatment. More work is needed to understand what underlies the link between ADHD and premature death.”
‘Life expectancy and years of life lost for adults with diagnosed ADHD in the UK: matched cohort study’ by Elizabeth O’Nions et al. was published in The British Journal of Psychiatry at 08:00 UK time on Thursday 23 January.
DOI:10.1192/bjp.2024.199
Declared interests
Prof Kevin Mcconway: Previously a Trustee of the SMC and a member of its Advisory Committee.
Prof Oliver Howes: has received research funding from and/or participated in advisory/ speaker meetings organised by Abbvie, Alkermes, Angellini, Autifony, Biogen, BMS (Karuna), Boehringer-Ingelheim, Delix, Eli Lilly, Elysium, Heptares, Global Medical Education, Invicro, Jansenn, Karuna, Lundbeck, Merck, Neumora, Neurocrine, Ontrack/ Pangea, Otsuka, Sunovion, Teva, Recordati, Roche, Rovi and Viatris/ Mylan. None of this was related to ADHD or its treatment.
For all other experts, no reply to our request for DOIs was received.