Self-harm

Self-harm is defined as non-fatal intentional self-poisoning or self-injury, regardless of motivation or intention. Events of poisoning and overdose with analgesics, although commonly implicated in suicidal behaviours, were not included as they are often accidental. We identify self-harm using all the concepts below in conjunction. These code lists are based on validated, published and comparable lists (Marchant et. al. 2020, Thomas et. al. 2014).

Related concepts

Self-Harm - Intentional (Aged 10+)

This includes all forms of intentional self-harm in those 10 years of age and older, from non-suicidal self-injury through to suicide attempts, with the exception of intentional alcohol poisoning or overdose. A small number of codes do not distinguish between non-fatal and fatal self-harm descriptors. We have included these for completion's sake. Fatal events could be removed if linked to mortality records.

In SNOMED CT, where additional codes were available they were maped as closely as possible to the previously validated Read and ICD-10 codes. As such, codes for self-poisoning are only included if they specifically state that the poisoning was both intentional and self-administered (e.g. ‘intentional self-poisoning by [drug]’, ‘intentional self-harm by poisoning’, ‘deliberate overdose’). Codes that indicate poisoning with no intent (‘poisoning by [drug]’, ‘self-poisoning by [drug]’), or intentional poisoning where it is not clear whether it was self-administrered or poisoning by another person (e.g. ‘intentional poisoning by [drug]’) have been excluded.

Self-Harm - Undetermined Intent (Aged 15+)

In this additional list we include events of undetermined intent for hanging, strangulation and suffocation; rifle shotgun and larger firearm discharges; other and unspecified firearm discharges; and falling and jumping from a high place in those 15 years of age and older, as they are likely unidentified self-harm events.

In primary care only, when intent is not explicitly recorded (neither intentional nor undetermined), we include events of overdose of drug, biological substance or medicament (without further substance specification) and poisoning and overdose of antidepressants (commonly implicated in suicide) also for those 15 years of age and older, as they are also likely unidentified self-harm events.

Self-Harm – Poisoning of Undetermined Intent (Aged 15+)

In primary care, extended Read codes “SL...14 – Overdose of biological substance” and “SL...15 – Overdose of drug” should also be considered as codes of undetermined intent. However, codes in extended form are not always available. When this is the case, we have found that the simpler version “SL… - Poisoning” may be used as a compromise solution to improve sensitivity at the expense of specificity (Marchant et. al. 2020).

Similarly, “SLHz. - Drug and medicament poisoning NOS” may be included as a code of undetermined intent (Thomas et. al. 2014).

History of Self-harm

Codes denoting previous self-harm (e.g., sequelae, late effect) in the above concepts are provided separately.

References

Marchant, A. Turner, S. Balbuena, L. Peters, W. Williams, D. Lloyd, K. Lyons, R. & John, A. 2020. “Self-Harm Presentation across Healthcare Settings by Sex in Young People: An e-Cohort Study Using Routinely Collected Linked Healthcare Data in Wales, UK.” Archives of Disease in Childhood 105(4):347-54.

Thomas, K. H. Davies, N. Metcalfe, C. Windmeijer, F. Martin, R. M. & Gunnell, D. (2013). Validation of suicide and self-harm records in the clinical practice research datalink. British Journal of Clinical Pharmacology, 76(1), 145-157.

How to use

To identify self-harm events, include all presentations at age 10 or older with code in Self-Harm - Intentional. Many UK National Health service and other official documents are based in this definition. However, validation studies have shown the benefit of also including presentations at age 15 or older with code in Self-Harm - Undetermined Intent and Self-Harm – Poisoning of Undetermined Intent (Thomas et. al. 2014). For poisoning of undetermined intent, be mindful of whether the data contains extended Read codes as described above.

When the time of the event is not critical (e.g., in prevalence calculations), include presentations with code in History of Self-Harm lists. Note, however, that these codes refer to past events and therefore it is not possible to enforce the relevant minimum ages (10+ and 15+). How to best approximate these criteria (e.g., 11+ and 16+) is left to the researchers and may require sensitivity analyses.

References

Marchant, A. Turner, S. Balbuena, L. Peters, W. Williams, D. Lloyd, K. Lyons, R. & John, A. 2020. “Self-Harm Presentation across Healthcare Settings by Sex in Young People: An e-Cohort Study Using Routinely Collected Linked Healthcare Data in Wales, UK.” Archives of Disease in Childhood 105(4):347-54.

Thomas, K. H. Davies, N. Metcalfe, C. Windmeijer, F. Martin, R. M. & Gunnell, D. (2013). Validation of suicide and self-harm records in the clinical practice research datalink. British Journal of Clinical Pharmacology, 76(1), 145-157.