Attempting to disentangle the relationship between impulsivity and longitudinal self-harm: Epidemiological analysis of UK household survey data.

Background: Impulsivity may be an important risk factor in terms of future self-harm. However, the extent of this, whether it may relate to self-harm that is new in onset and/or repetition of self-harm, and the detail of any interaction with mood instability (MI) and childhood sexual abuse (CSA) requires detailed examination.

Aims: We used the 2000 Adult Psychiatry Morbidity Survey and an 18-month follow-up data to test hypotheses relating to the role of impulsivity, CSA and MI in the inception and persistence of self-harm.

Methods: We assessed associations of impulsivity with (1) suicidal self-harm (SSH) and (2) non-SSH (NSSH) at baseline and follow-up, controlling for confounders including MI. Finally, we tested whether impulsivity mediated the relationship between CSA and self-harm.

Results: A total of 8,580 respondents were assessed at baseline and 2,406 at follow-up as planned. Impulsivity significantly predicted emergence of new NSSH at 18-month follow-up even after adjustment for MI and other confounders. Impulsivity did not significantly predict repetition of NSSH, or repetition or new inception of SSH, even before inclusion of MI in the model. However, the absolute numbers involved were small. Cross-sectionally, impulsivity was a stronger mediator of the link between CSA and SSH (13.1%) than that between CSA and NSSH (4.8%).

Conclusion: Impulsivity may increase the risk of future development of NSSH independently of MI, which is clinically important for risk assessment. The involvement of impulsivity in the repetition of self-harm generally appears less certain. However, impulsivity may have a role in SSH in the context of previous CSA.