How do the prevalence and relative risk of non-suicidal self-injury and suicidal thoughts vary across the population distribution of common mental distress (the p-factor)? Observational analyses replicated in two independent UK cohorts of young people

Ela Polek, Sharon Neufeld, Paul Wilkinson, Ian M Goodyer, Michelle St Clair, Gita Prabhu, Raymond J. Dolan, Edward T Bullmore, Peter Fonagy, Jan Stochl, Peter B Jones

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Importance: Suicide is the second ranked cause of deaths among 10 to 24 year-olds, worldwide. Clarity over the relationships between mental state and suicide risk, measured here by suicidal thoughts (ST) and non-suicidal self-injury (NSSI), will guide clinical and public health responses.
Objectives: To inform suicide prevention policies and responses to youths at risk by investigating whether suicide risk is predicted by a summary measure of common mental distress (CMD) as well as by conventional psychopathological domains; to define the distribution of suicide risks over the population range of CMD; to test whether such distress mediates the medium-term persistence of suicide risks.
Design: Two independent samples of young people studied during three sweeps: the Neuroscience in Psychiatry (NSPN) 2400 cohort (n=2403) and the ROOTS cohort (n=1074); Cohorts 1 and 2, respectively.
Setting: Population-based in two UK centres.
Participants: Volunteers age 14-24 years recruited from primary health care registers, schools and colleges; advertisements to complete quotas in age-sex-strata.
Method: We analysed questionnaire data from Cohort 1 (sweeps 1-3) and Cohort 2 (sweep 3), collected between November 2012 – December 2016 and February 2008 – December 2009, respectively. We calculated a CMD score using confirmatory bifactor analysis; used logistic regressions to determine adjusted associations between risks and psychopathology (in continuous and above-the-norm categorical format); curve-fitting to examine the relative prevalence of ST and NSSI over the population distribution of CMD; and pathway mediation models to examine longitudinal associations.
Results: We found a dose-response relationship between levels of CMD and risk of suicide. The majority of all subjects experiencing ST and NSSI (Cohort 1 78% and 76%; Cohort 2 66% and 71%, respectively) had CMD scores no more than two standard deviations above the population mean; higher scores indicated highest risk but were, by definition, infrequent. CMD mediated the longitudinal course of both suicide risks.
Conclusions. NSSI and ST in youths reflect common mental distress that also mediates their persistence. Universal prevention strategies reducing levels of CMD in the whole population without recourse to screening or measurement may prevent more suicides than approaches targeting youths with the most severe distress or with psychiatric disorders.
Original languageEnglish
JournalBMJ Open
Publication statusAccepted/In press - 30 Mar 2020

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