Changing patterns of substances involved in poisonings among young people in England: a large population based cohort study

Problem

Estimates suggest that 7-12% of young people in the UK have self-harmed, with 84-96% of medically attended self-harm episodes being poisonings. Although reported within secondary care samples, up-to-date population level data on the substances involved in poisoning episodes are lacking. This information is needed to help prevent self-harm amongst young people. This study used routine primary care data, linked to hospital admission and mortality data to assess the patterns and trends in substances involved in poisoning episodes among 10-24 year olds across England.

Approach

An open cohort study of 1,736,527 young people aged 10-24 between 1998 and 2014 was conducted using data from the Clinical Practice Research Datalink, linked to Hospital Episode Statistics and Office for National Statistics mortality data. Poisoning substances were identified by relevant ICD10 or Read codes. Incidence rates and adjusted incidence rate ratios (aIRR) with 95% confidence intervals (95%CI) were calculated for poisonings by age, sex, index of multiple deprivation (IMD) and year according to the substances involved.

Findings

A total of 40,333 poisoning episodes were recorded during the study period, of which 76% included a medicinal substance and 58% had the precise substances involved in the poisoning specified. The most common substances involved were paracetamol (40%), alcohol (33%), non-steroidal anti-inflammatory drugs (NSAIDs) (16%), antidepressants (13%) and opiates/psychodysleptics (12%). After adjusting for sex, age, IMD and area of England, overall recorded poisoning rates increased by 25% between 1998 and 2014 (aIRR 1.25, 95%CI 1.20-1.30). However, very different patterns were demonstrated according to sex, age and poisoning substance. For most substances rates were highest amongst 16-18 year olds for females and 19-24 year olds for males. The greatest increases over time were seen amongst females aged 16-18 for a range of substances: paracetamol poisonings increased three-fold (171.6 per 100,000 person-years (PY) in 1998/99 to 501.3/100,000 PY in 2013/14); NSAID poisonings increased 2.7 fold (62.0/100,000 PY in 1998/99 to 170.0 in 2013/14); and opiate/psychodysleptic poisonings increased 13.6 fold (9.5/100,000 PY in 1998/99 to 129.2 in 2013/14). Alcohol poisonings amongst boys aged 10-15 were the only ones to decrease over time (94.4/100,000 in 1998/99 to 31.2 in 2013/14). Poisoning rates increased with increasing deprivation for each of the seven most common substances (58% to 3-fold increased risk for the most compared to least deprived quintile).

Consequences

Volumes of medication prescribed to young people should be limited, especially for those with a history of self-harm, where similar precautions should be taken when prescribing for family members. This is important when prescribing for psychiatric and non-psychiatric conditions, especially analgesics. Families and carers of those at risk of self-harm should be warned to consider the availability of over-the-counter medication to young people, given their common involvement in poisonings.