Design

This is a retrospective cohort study of self-poisonings and psychotropic dispensings in Australians aged 5–19 years. Poisons Information Centre (PIC) data provide up to date and detailed information on self-poisoning behaviours. Australia has four PICs, together providing nationwide poisoning advice to healthcare professionals and members of the public. We used data from the NSWPIC and Victorian PIC (VPIC), which together take approximately 70% of the nation’s 200 000 yearly poisoning calls. For the purposes of this study, a ‘child’ is defined as someone aged 5–14 years, and an ‘adolescent’ is between the ages of 15 and 19 years (as PICs use these categories when coding calls).

We also used psychotropic dispensing data, as a separate proxy measure for mental well-being. For the purposes of this study, psychotropic pharmaceuticals included antidepressants, benzodiazepines, antipsychotics, psychostimulants and clonidine. Australia has a publicly funded universal healthcare system, with subsidised medicines available to citizens and permanent residents under the Pharmaceutical Benefits Scheme (PBS). We used PBS dispensing data from a random 10% sample of PBS-eligible Australians. This nationwide data source has been described in detail previously.18 This is a standard dataset provided by the Australian Government Department of Human Services and is the gold standard for pharmacoepidemiology research in Australia.

Data sources

Patient and public involvement

This was a retrospective review of routinely collected data. Patients and the public were not involved in the design or the recruitment of the study.

Data access approvals

Access to the PBS 10% sample was approved by the Australian Department of Human Services External Request Evaluation Committee.

Intentional poisonings

In the 11-year study period, the NSWPIC and VPIC databases recorded 8053 intentional poisonings in individuals aged 5–14 years and 25 448 intentional poisonings in those aged 15–19 years (total 33 501 poisonings in people aged 5–19 years). Numbers of self-poisonings in those aged 5–19 years increased by 8.39% per year (95% CI 6.08% to 10.74%, p<0.0001), with an overall increase of 98%, 2006–2016 (figure 1). Self-poisonings in children increased by 9.00% per year (95% CI 6.26% to 11.81%, p<0.0001), overall 107%, 2006–2016. Adolescent self-poisonings increased by 8.21% per year, (95% CI 5.96% to 10.5%, p<0.0001) or 96% over the study period. By comparison, we observed an overall increase of 15% in self-poisoning in persons aged 20 years and over, 2006–2016. In children and adolescents, self-poisonings for females outnumbered those for males by 3–1 (figure 1). Self-poisoning in females increased by 108% in total, 9.21% per year, (95% CI 6.63% to 11.86%, p<0.0001), while in males increased by 72% in total, 6.03% per year (95% CI 3.96% to 8.14%, p<0.0001).

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Figure 1

Trends in intentional poisonings in children and adolescents reported to the NSWPIC and VPIC, 2006–2016. NSWPIC, New South Wales Poisons Information Centre; VPIC, Victorian Poisons Information Centre.

Self-poisoning increased dramatically and is consistently higher in those born after 1997 (figure 2), indicating a birth cohort effect. Overall, substances most commonly used in self-poisoning episodes included analgesics (including those available without a prescription) and psychotropics (table 1); many exposures were to medicines where use in children/adolescents is ‘off-label’. Time trends in exposures to agents broken down by broad substance classes (online supplementary figure 1) show large increases in poisonings with psychotropics and non-narcotic analgesics.

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Figure 2

Number of intentional poisonings by birth year cohort at ages 5–19 years, 2006–2016.

Psychotropic dispensing

We observed increases in the number of individuals aged 5–19 dispensed specific psychotropic medicines. From July 2012 to June 2016, selective serotonin reuptake inhibitor (SSRI) dispensing increased 40% and 35% in those aged 5–14 and 15–19, respectively (table 2, figure 3). Males received ~60% of antidepressants in the age group of 5–14 years. Conversely, in those aged 15–19, females received 65% of antidepressant dispensings (table 2, figure 3). Fluoxetine was the most dispensed SSRI across both genders and age groups (increasing 54% and 44% in those aged 5–14 and 15–19, respectively). Escitalopram, fluvoxamine and sertraline were also commonly used in the older age group. Use of other antidepressant classes was lower, although venlafaxine and mirtazapine increased 27% and 34%, respectively, in those aged 15–19 (table 2). Males received ~80% of antipsychotics in the age group of 5–14 years, decreasing to ~60% in the age group of 15–19 years (table 3). Trends in antipsychotic dispensing in people aged 5–19 show that risperidone and quetiapine are the most used, with a 19% increase in risperidone dispensing (table 3). In people aged 5–19 years, 80% of ADHD medication dispensing was to males. ADHD medicine dispensing has increased 14% in people aged 5–19, with clonidine and methylphenidate dispensing increasing 26% and 17%, respectively. Conversely, dispensing of benzodiazepines to this age group is relatively uncommon and has decreased by 6%. Females were dispensed ~60% of benzodiazepines. Longer term trends (2006–2015), without under copayment data are displayed in online supplementary figures 2–4, indicating that these recent changes are largely an extension of longer term trends.

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Figure 3

Rolling average of SSRI prevalence (persons/10 000 population/month), in females and males aged 5–14 years (A and B, respectively), and females and males aged 15–19 years (C and D, respectively), July 2012 to June 2016. Data were not shown for medicines where there were <30 persons in 10% sample on that class in at least 1 month examined. SSRI, selective serotonin reuptake inhibitor.

Strengths and limitations

These results should be viewed in light of the strengths and limitations of this study. As discussed above, there have been recent reports of increases in adolescent self-harm presentations to emergency departments in NSW and Victoria (Australia’s two most populous states). Hospital presentation data have limited sensitivity, and many self-poisonings may be coded as the presenting symptom.20 Even when self-poisonings are identified, the agents involved cannot be well classified with clinical coding systems (such as The International Statistical Classification of Diseases and Related Health Problems, tenth revision (ICD-10) and Systematized Nomenclature of Medicine - Clinical Terms (SNOMED-CT)), and are generally coded under broad pharmacological groups. PIC data provide up-to-date data on self-poisonings in Australia with detailed capture of substances involved. Substances are coded in real time by specialists in poisons information (pharmacists and pharmacologists with postgraduate toxicology training) to a high standard. Capture of substances taken in overdose is much more detailed than routinely collected hospital presentation/admission data. Coding of exposure intent has been stable with time, with a categorisation of exposure intent (accidental, intentional) collected reliably since the early 1980s. Each call is reviewed within 12 hours by a colleague to further enhance accuracy. In addition, the increases observed in this study are on the background of decreasing overall calls to PICs,21 and thus could not be explained by increased service utilisation. There have been no changes in referral practices/PIC utilisation that could explain a surge in calls.

Another strength of this study is its capture of over a decade’s worth of data from two of Australia’s poisons centres, amounting to ~70% of the nation’s poisoning calls. This includes almost complete capture of poisons calls for the South East of Australia, plus some calls from the rest of the nation (due to the on-call structure shared by Australian PICs). NSWPIC and VPIC receive calls from members of the public and healthcare professionals across Australia and thus may provide better estimates of trends than studies conducted out of single hospitals. However, this is not a complete capture of all child/adolescent poisonings as calls to the PIC are voluntary, some hospitals may not call a PIC when a poisoning case presents, particularly those with local toxicology services or those staffed by experienced emergency physicians. Thus, this represents a conservative estimate of actual incidences of self-poisoning.

PBS data enable analysis of trends in the medicine dispensing on a nationwide scale but does not capture private scripts. However, it is estimated that private scripts account for less than 10% of dispensings in Australia.22 Due to PBS data capture changes, our primary analysis was on dispensings from 2012 onwards.

Comparison with other studies

This study signals a concerning increase in child/adolescent self-poisoning in Australia. Similar findings have been reported elsewhere in the world5–7 23 indicating that this may be a global trend. A 2015 global burden of disease study ranked the top 25 causes of death worldwide in children. Globally, in children 10–14 years, self-harm was ranked 13th and 12th in girls and boys, respectively. A similar picture is seen globally in adolescents aged 15–19 years, where self-harm is ranked second and third in females and males, respectively. Self-harm was not in the top 25 causes of death in children aged 5–9 years.24 Thus, self-harm is a substantial contributor to disease burden in children and adolescents worldwide. Any increase on this high base will have substantial overall effects on public health.

We have demonstrated large increases in certain psychotropic dispensings in those aged 5–19 years, particularly in antidepressants and antipsychotics. Unsurprisingly, psychotropics were commonly taken in overdose by this age group. Karanges et al recently described trends in psychotropic medicine use in Australians, 2009–2012. Dispensings of antidepressants and antipsychotics in children 10–14 years of age increased at a faster rate than in any other age group (35.5% and 49.1%, respectively).13 This increased prescribing is not a uniquely Australian trend, with increases in antipsychotic use also documented in the USA10 and the UK.12 Use of antidepressants in children has remained stable in the USA, however, is increasing in the UK.11 In Canada, antipsychotic use in children 18 and under increased fourfold, 1998–2008, with the largest increases in those aged 7–18 years.25 In Denmark, psychotropic use in children 0–17 years increased ninefold, 1996–2010 (twofold increase when adjusting for increasing patient numbers).26 A review of international trends in psychotropic medication use in children and adolescents found a general trend in many countries of increasing prescription rates.27 This increase in utilisation is despite only limited evidence for efficacy in these age groups, and concerns regarding potentially increased risk of suicidal ideation and self-harm.17

Implications and future directions

For those seen in the hospital, the estimated rate of repetition of non-fatal deliberate self-harm is 16% at 1 year, while a rate of suicide is 1.6% at 1 year and 3.9% at 5 years.28 A recent study of completed suicides in England in people under 20 reported that more than half had previously self-harmed.29 Thus, the patients in our study are at risk of repetition and completed suicide later in life.

The striking cohort effect observed here raises many questions about what is driving this trend. One could speculate that recent technological advancements have a role. Rising internet, social media and smartphone usage among young people could impact on mental health and responses to distress. The percentage of Australian teens who use a smartphone has increased from 23% to 80%, 2011–2015 (similar percentages are seen in teenagers in the USA and UK).30 Increasing rates of self-harm could be due to increased mental illness in this population or changing behavioural responses in this cohort. Self-harm and suicidal contagion is a well-documented phenomenon. New media (eg, prosuicide websites normalising self-harm) could facilitate this contagion. Cyberbullying and internet use, in general, has been found to correlate with self-harm, suicide and mental illness.31 Conversely, the internet may exert positive effects on young people at risk of self-harm, and there is great potential in new media for promoting positive mental health and coping strategies.31

People who self-poison often do this with medicines prescribed for them.14 Of the most common substances involved in self-poisoning listed in table 1, there is considerable overlap with leading psychotropics dispensed (tables 2 and 3), including fluoxetine, quetiapine, sertraline, escitalopram, methylphenidate, venlafaxine, fluvoxamine, risperidone, olanzapine and desvenlafaxine. Given the potential increase in suicidal ideation and behaviours in young people taking SSRIs, serotonin–norepinephrine reuptake inhibitors and ADHD medicines,16 this could be a potential contributor to increasing self-poisoning attempts. Many of these medicines (including venlafaxine, desvenlafaxine) are not recommended in children according to current guidelines, and observed increases may be a result of marketing practices.13 However, our results show some attempt to adhere to guidelines. Fluoxetine is the first-line treatment for depression in children and adolescents, and is the most prescribed antidepressant in this age group.

Given that there is little evidence for the efficacy of most psychotropics in this age group, their prescription should be carefully considered. If a psychotropic is prescribed, where possible, agents that are toxic in overdose (eg, citalopram, escitalopram, amisulpride,32 venlafaxine33 and quetiapine34) should be avoided. Prescribers should be vigilant for signs of anxiety or depression in their patients and keep medicine supplies to a minimum when prescribing to patients believed to be at risk of self-harm.

Importantly, we observed high rates of poisonings with readily available over-the-counter medicines, with paracetamol and ibuprofen being the top two substances used in self-poisonings in this age group. When compared with adults (aged 20 and over), children and adolescents are more likely to use over-the-counter medicines in intentional poisonings.35 Paracetamol poisoning is the leading cause of acute liver failure in Western countries.36 In Australia, paracetamol can be in 100×500 mg (50 g) and 96×665 mg (modified release, ~64 g) packs in pharmacies and 20×500 mg packs (10 g) outside of pharmacies. Previous studies have demonstrated that paracetamol overdoses are often impulsive and involve the use of paracetamol present in the home.37 In 1998, the UK restricted paracetamol pack sizes in response to increasing overdoses, liver transplants and deaths. Sales were restricted to 16 g within pharmacies or 8 g outside of pharmacies. This legislation appears effective, with a subsequent reduction in large overdoses, liver unit admissions and deaths in England and Wales.38–40 Although we did not assess outcomes of the paracetamol poisonings in our sample, similar means restriction in Australia could be implemented to reduce harm from paracetamol overdose.

The increase in self-poisoning and psychotropic use in this cohort raises three possibilities: (1) psychotropic prescribing predates self-poisoning and may increase suicidal ideation/self-harm tendencies; (2) psychotropic medicines are being prescribed following a self-harm attempt and (3) unrelated increase in self-poisoning and psychotropic medicines as independent markers of mental distress in this cohort. These are long-standing issues but our data demonstrate that it is increasingly important that these relationships are better characterised. Interestingly, males received the majority of antidepressant dispensings in the age group of 5–14 years, and yet females in this age group were more likely to self-poison, providing some information to support point (3) above, at least in younger children. Future studies using linked data to better characterise the relationship between psychotropic prescribing and self-harm/suicide could provide valuable insights into which of these three explanations is most likely.