Response

We read the paper by O’Nions et al ^{Reference O’Nions, El Baou, John, Lewer, Mandy and McKechnie1} with interest. The bottom-line result of the study was that adults diagnosed with attention-deficit hyperactivity disorder (ADHD) in the UK have a significantly reduced life expectancy compared with the general population. However, what caught our attention is that, contrary to our expectations, life expectancy for males was higher than that for females. While the authors discuss the possible reasons for the disparity in life expectancy for people living with adult ADHD compared with the general population, they do not discuss the disparity between males and females.

In appraising this paper, we think that the disparity in results for males and females is affected by several factors. The diagnosis and initial treatment of adult ADHD in the UK tends to happen either in tertiary services, where they exist, or in secondary care. ^{Reference Smith, Mukherjee, Müller-Sedgwick, Hank, Carpenter and Adamou2} In order to access these services, patients would have to be referred by their primary or secondary care providers. These professionals are more likely to recognise or suspect ADHD in males. This may be because males tend to present with more externalising behaviours (such as aggression and risk taking), while females may experience more internalising symptoms, such as anxiety and depression. ^{Reference Gershon3,Reference Lau, Lim, Acharryya, Lim-Ashworth, Tan and Fung4} Hence, males may be more likely to receive interventions that reduce risks, treat co-occurring conditions and, invariably, increase their life expectancy.

The selection of participants for the study was practical but was affected by selection bias, by which those under study were the diagnosed; however, the diagnosed are limited by professionals’ knowledge, skills and referral practices.

In Ontario, Canada, ADHD is routinely diagnosed and treated in primary care, as allowed for in the Canadian ADHD Practice Guidelines. ⁵ This is necessary given the comparative shortage of psychiatrists in the country. Consequently, a primary care population to be sampled here would be expected to be greater in number, and probably more complex in presentation, than that obtainable in the UK. Given the earlier access to treatments, we hypothesise that this study, if carried in our community, may have produced different results with better life expectancy across the board and a lesser gap between the sexes.