‘1 in 4’ prevalence for psychiatric disorder…or should that really be ‘1 in 3’? Parity of esteem in statistical headlines

Bebbington & McManus are to be thanked and congratulated for keeping this important and popular, but slippery, statistic under regular review and close-examination.¹ Their summary is likely to lead most readers to continue using the now well-known and oft-quoted ‘1 in 4’ headline statistic for the overall prevalence of psychiatric disorders. They also rightly point out the twin dangers of over- and under-egging the statistic, risking lack of credibility and lack of impact, respectively.

However, I would suggest that the data presented comfortably allows for a new, revised ‘1 in 3’ headline. This would not be overstating the case, but would simply accurately describe their findings. Their current ‘1 in 4’ summary headline explicitly excludes ‘personality and other disorders’, as well as ‘substance use disorders’ and ‘developmental disorders’ …including them takes the true statistic to (very nearly) ‘1 in 3’ (31.6%, to be precise).

There is now a long history of evidence and campaigning to have personality disorders recognised as ‘bona-fide’ mental disorders, with services developed and provided to match. Calls range from the 2003 National Institute for Mental Health in England ‘Personality Disorder: no longer a diagnosis of exclusion’,² through to the more recent 2018 consensus statement on personality disorder³ and the freshly released 2020 Royal College of Psychiatrists Position statement, ‘Services for People Diagnosable with Personality Disorder’.⁴ They have always been in the ICD-10. Similar arguments and evidence could be made (ethically, on the grounds of stigma/parity, and scientifically) for the inclusion of the substance use disorders and developmental disorders that bring the final statistic to 1 in 3.

Presenting a new ‘1 in 3’ headline would not be over-egging the evidence, but simply presenting the full findings of carefully conducted up-to-date research, thus promoting accurate, evidence-based societal perceptions of mental disorder, and subsequent policy decision-making. This is especially important given the limited traction so far gained in closing the gap between rhetoric and action with regard to ‘parity of esteem for mental health’.⁵ The NHS Long Term Plan for Mental Health⁶ carries the potential for hope, but nothing should be taken for granted until it materialises.

In the meantime, we should advocate not excluding people with personality disorder (or substance use and developmental disorders) from the headline statistics generated by good-quality research; statistical parity of esteem for all those with mental disorders would justify a new, revised, evidence-based and accurate ‘1 in 3’ summary headline, which would be neither under-egged, nor over-egged, but ‘just(-ly) right’.