By Elystan Roberts
Everyone who has ridden the rollercoaster of pubertal development knows just how difficult it can be. Between the ages of 10 and 20, our bodies and brains undergo some of the most substantial changes of our lives. Alongside managing huge fluctuations in circulating sex hormones and fundamental neurocognitive change, we face new social and interpersonal challenges as we test and refine our emergent sense of self.
So it’s no wonder that the pubertal years see the highest incidence of self-harm across our whole human lifespan, with recent studies estimating that nearly 1 in every 5 young people aged 12-17 report having self-harmed . As well as being a huge concern in its own right, self-harm is also one of the strongest predictors of later suicide , so research into the factors which increase the risk of self-harm is essential.
While we know that puberty is a time of drastic change, the intricacies of its association with self-harm are unclear. One important piece of the puzzle is pubertal timing; when someone experiences puberty compared to their peers has been linked to outcomes like depressive symptoms , conduct problems , and eating disorders . I am interested in whether pubertal timing is associated with self-harm risk: does when you experience puberty influence how likely you are to self-harm?
Here’s how a team of us in Bristol have tried to answer that question, using data from a large cohort of individuals from the Bristol area, called the Avon Longitudinal Study of Parents and Children (ALSPAC).
Study 1: Girls
It’s a lot easier to measure the timing of puberty in girls than in boys, because girls experience a pubertal event that distinctly happens for the first time at puberty, is easy to remember, and reliable to self-report: menarche – the first menstrual period, to you and I. In our first study , we took the age at which girls reported experiencing their first period and examined whether it was associated with self-reported self-harm at 16 and 21 years of age.
We found that the earlier girls experienced menarche, the higher their risk of self-harm. Compared to individuals who experienced menarche at the average age, those who experienced early menarche were more likely to report self-harm and, conversely, those who experienced late menarche were less likely to report it.
So, experiencing earlier puberty is a risk factor for self-harm in girls.
Study 2: Boys and girls
We then wanted to see whether the results we found for girls also applied to boys, and to do this it was important to use a reliable measure of pubertal timing. Luckily, ALSPAC has measured participants across their whole lives, so there are multiple measures of participants’ height as they grew up. This allowed us to calculate their peak height velocity, or adolescent growth spurt – the age when an individual’s height is growing the fastest.
Age at peak height velocity is related to puberty, and is correlated with other puberty measures like menarche. In addition, participants’ height measures were taken by trained research nurses, so the data is objective. We examined whether age at peak height velocity was related to self-harm reported at age 16 and 21 years, in both boys and girls.
We found that earlier age at peak height velocity was associated with a higher risk of self-harm in both sexes. For boys, compared to individuals with an average age at peak height velocity, those with an early age at peak height velocity were at increased risk of self-harm, while those with late age at peak height velocity were at reduced risk.
So, experiencing early puberty is a risk factor for self-harm in both boys and girls.
What is it about early puberty?
We don’t know exactly why early puberty is related to a higher risk of self-harm. There are a number of possible explanations, and it is likely to be more than one. It could be due to an increased risk of affective disorders like anxiety or depression: we know that early puberty is related to depressive symptoms, perhaps through the influence of sex hormones , and this may explain the higher risk of self-harm in individuals who experience early puberty. Alternatively, we also know that individuals who experience early puberty are more likely to associate with older peers who are developmentally similar to them. This means they are more likely to experience risk factors for self-harm – things like sexual relationships and drug and alcohol use – at an earlier age. But it could also be due to a feeling of isolation: individuals experiencing puberty before their peers may have nobody to talk to about it; they may feel they have nobody to relate to or support them through the changes. This last suggestion is credited to the group of candid, insightful adolescents with whom I was lucky enough to recently run a PPI workshop.
We’ve found that experiencing puberty before your peers is related to a higher risk of self-harm in both girls and boys. There are a number of possible explanations for this, and we are currently looking at some of these possible factors to try and explain the association between puberty and self-harm in more detail. In future, some of these factors could be the targets of interventions aimed at reducing self-harm risk in individuals who experience early puberty.
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Elystan Roberts is a PhD student based at the school of Population Health Sciences at the University of Bristol, UK (firstname.lastname@example.org).