Changes in adolescent poisonings in the UK over the past 20 years: a population based cohort study

The problem

It is estimated that 7-12% of adolescents in the UK have self-harmed, with 84-96% of medically attended self-harm episodes being poisonings. However, the factors that increase the risk of adolescent poisoning have not been well described with few data on how incidence has altered over time. This study used routine primary care data to assess this in a UK adolescent population.

The approach

An open cohort study of 1,311,021 adolescents aged 10-17 between 1992 and 2012 was conducted using routinely collected primary care data from The Health Improvement Network. Incidence rates of all poisoning events were calculated by age, sex, 5-year time bands and by quintile of socio-economic deprivation measured by the Townsend index. Multivariate negative binomial regression was used to calculate mutually adjusted incidence rate ratios (IRR) with 95% confidence intervals (CI).

Findings

Overall poisoning incidence increased by 27% from 264.1/100,000 person years (PY) in 1992/96 up to 346.8/100,000 PY in 2007/12, with the largest increases in intentional and alcohol-related poisonings (52% and 19% respectively), a 6% increase in unknown intent poisonings, but a fall of 46% for accidental poisonings. In 2007/12 64% of poisonings were classified as intentional, 16% alcohol-related, 16% unknown intent and 4% accidental.The socioeconomic gradient of poisonings remained unchanged between 1992/96 and 2007/12 (IRRs 2.83, 95% CI 2.36-3.40 and 2.63, 95% CI 2.41-2.87 for the most compared to the least deprived group in respective time bands). This gradient increased in alcohol-related (IRRs 2.17, 95% CI 1.52-3.09 and 3.11, 95% CI 2.55-3.80 respectively) and unknown intent poisonings (IRRs 1.63, 95% CI 1.10-2.40 and 2.92, 95% CI 2.25-3.77 respectively), remained unchanged for accidental poisonings and reduced for intentional poisonings (IRRs 4.37, 95% CI 3.32-5.74 and 2.53, 95% CI 2.26-2.83 respectively).Between 1992/96 and 2007/12 alcohol-related poisoning rates increased more amongst females (45.9 to 62.8/100,000 PY respectively) than males (45.4 to 49.2/100,000 PY respectively). There were no significant changes in the sex distribution of other poisoning types over time. Intentional poisoning rates increased most dramatically amongst 16 and 17 year olds over this period (407.4 to 617.3/100,000 PY respectively for 16 year olds). Alcohol-related poisoning rates increased in the 15-17 year age groups (56.0 to 93.8/100,000 PY respectively for 16 year olds) but fell for 10-11 year olds (16.3 to 4.6/100,000 PY respectively for 11 year olds). Accidental poisonings fell in all age groups between 1992/96 and 2007/12.

Consequences

The incidence of adolescent poisonings, especially intentional poisonings, has increased substantially over the last 20 years and a strong socioeconomic gradient remains today. Social and psychological support for adolescents should be targeted at more deprived communities, as well as child and adolescent mental health service provision being commissioned to reflect the changing need.

Credits

• Edward Tyrrell
• Elizabeth Orton
• Laila Tata