Advanced Statistical Analyses

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    Time Series Data and Examining the Impact of the Economic Recession on Suicide Attempts and Self-Harm

    As an example of the value of time series data, an in-depth analysis including data from the National Self-Harm Registry Ireland found that, during the period 2008−2012, there was a negative impact of the economic recession on national rates of suicide and self-harm (including suicide attempts) in Ireland (6). In order to quantify the impact of this change, the study compared the observed rate of suicide and self-harm with the rate that would have been observed had the decreasing trend of suicide rates continued (i.e. if the rates of suicide and self-harm had continued to decline as they had been doing).

    Interrupted time series analysis (7) was performed to test if the recession had an impact on the level and trends of suicide and self-harm. The first time period of 2008 was taken as the advent of the recession. The analysis was repeated using two different recession starting points (Quarter 3/July 2007 and Quarter 3/July 2008) in order to assess the sensitivity of the results.

    The results indicated that five years of economic recession and austerity in Ireland had a significant negative impact on rates of suicide in men and on self-harm in both sexes. The findings highlight the need to guide government responses to economic recessions in relation to suicidal behaviour and other health outcomes.


    Time Series Data and Examining the Risk of Repeated Self-Harm and Suicide

    Data collected in the Multicentre Study of Self-harm in England covered all self-harm hospital presentations by individuals aged 10–18 years between 2000 and 2007, and national death information on these individuals to the end of 2010 (8). Cox hazard proportional models were used to identify independent and multivariable predictors of repetition of self-harm (including suicide attempts) and of suicide.

    Self-cutting as a method of self-harm in children and adolescents was reported to convey greater risk of suicide and repetition of self-harm than self-poisoning although different methods are usually used for suicide. The findings underline the need for psychosocial assessment in all self-harm cases presenting to general hospital.

    Time series data and examining the trends in suicide attempts and changes in risk factors Data from the USA’s National Hospital Ambulatory Medical Care Survey included all visits for attempted suicide and self-inflicted injury (E950–E959) during 1993–2008 (9).

    Trend analyses were conducted using nptrend (a nonparametric test for trends that is an extension of the Wilcoxon rank-sum test) and regression analyses. A two-tailed P<.05 was considered statistically significant.