The Problem of Puberty

Puberty is alchemy, don’t you think? Like the chrysalis of a butterfly, the girl emerges from the pupal case of her childhood into an adolescent -an almost-woman- with hormones ablaze. It is a magic time of change, both in growth and physiology, but also in cognitive development. It is a time of evolving expectations, but more slowly developing judgement –the brain, too, is undergoing renovations. Hence our oft-aggrandized memories of the time –not deceptions, exactly, but distortions. To paraphrase Napoleon: history is the version of past events that I have decided to agree upon.

Many of the manifestations we see of puberty are the confusion of autonomies –the challenges to the boundaries that society imposes. I think Wikipedia has summarized the issues quite succinctly: ‘Psychologists have identified three main types of autonomy: emotional independence, behavioral autonomy, and cognitive autonomy. Emotional autonomy is defined in terms of an adolescent’s relationships with others, and often includes the development of more mature emotional connections with adults and peers. Behavioral autonomy encompasses an adolescent’s developing ability to regulate his or her own behavior, to act on personal decisions, and to self-govern. Cultural differences are especially visible in this category because it concerns issues of dating, social time with peers, and time-management decisions. Cognitive autonomy describes the capacity for an adolescent to partake in processes of independent reasoning and decision-making without excessive reliance on social validation.’ It is obviously a special and bewildering, albeit a magical  time. A time for planting the crop that is to come…

Because there are so many physiological processes involved, the actual start of puberty has always been approximate. Genes no doubt play a major role in its onset, but nutrition and general health are obviously involved as well because puberty is changing –it’s starting earlier. As an article from BBC news reports: The age of puberty is changing around the world. In the UK it is currently starting about one month earlier every decade. In China it is more than four months earlier every decade.

Of course, we have an almost obsessive need to analyze every change –to match every nuance with some overly reductionist, albeit plausible, explanation. Meat, for example. Yes, I’m serious:  Although it’s an older study, and Vegan-unreferenced, I have to wonder if they could have equally successfully used milk consumption, or perhaps eggs, or even Starbucks coffee… 

But whatever the causes of earlier puberty, that very change may have unexpected –and perhaps unwanted- ramifications as the MRC Epidemiology Unit  at the University of Cambridge recently published using the data of almost half a million people from the UK Biobank:

Doesn’t it seem strange that improving health and nutrition could have untoward, unintended consequences, although somewhat removed in time and maturity? Perhaps targetable with preventive interventions to be sure, as the authors point out in their abstract, but nonetheless ironic –the Red Queen needing to run faster and faster to stay in the same spot…

The most convincing evidence of the effect of an earlier puberty, apparently, is in its association with higher risks for type 2 diabetes and cardiovascular disease in women. A simple reasoned path to the type 2 diabetes (and its well known association with obesity) might be that: ‘early childhood rapid growth and overweight precede early puberty timing in both sexes, but in turn early puberty timing leads to subsequent rapid gains in weight and adiposity during adolescence and early adulthood’, but this may be an over-simplification of one of many factors that may be contributing –longer exposure to hormones, say, or life-style decisions altered by earlier maturation than peers: ‘environmental stressors may precede early puberty, but in turn early puberty leads to more risk taking behaviours and poor school performance.’ Intriguing, but speculative to say the least.

And on the more optimistic side of changing pubertal age? Well… there is a trend towards a lower risk for breast cancer in those with a later onset of puberty –although in fairness, this is likely related to a decreased time of exposure to hormones, so I’m not sure if it isn’t just a bit of trade-off… And anyway, trend is often what you call something that is not statistically significant (and yet perhaps lends credence to your hypothesis?).

But are we simply treading water in storm-tossed seas?  At risk of drowning in the details of semi-focused data swirling around us –most of which, at least in this case, was dependent on self reported medical histories and events that happened years before? Admittedly, the age of the first period is probably recalled with fair accuracy by most women –it is an event like few others- but aren’t researchers as seduced by this form of reasoning as the rest of us: the development of diabetes just begging for a scapegoat? So, choose the goat, widen the parameters, and voila…

An illustrative example of how easy it is to be led astray: many years ago, before we knew very much about the causal agent for cancer of the cervix (it is now known to be the human papilloma virus) but had pretty well decided it was something infectious –something sexually transmitted at any rate- the herpes virus came under scrutiny. It was infectious; many women exhibiting it also had abnormal pap smears suggesting precursor lesions for cervix cancer; and it was obvious –women who developed herpes were almost always aware of it. Herpes was easy to blame, because it was fairly straightforward to date the pap smear problem to some time after the event of acquisition. Everything fit –except it was not the cause. Not only did people who had never experienced herpes also develop abnormal pap smears, but similarly, not all people with herpes developed pap smear changes. The recall was an easy data point -something to blame- it’s just that it was the wrong thing.

My point is, it can be misleading to attribute cause merely based on recallable events. We all require explanations -something to blame. But, Post hoc ergo propter hoc? Well, the Latin may sound authoritative but not in Medicine. It is a logical fallacy…

This is all unfair to the study I know; I don’t mean to cast aspersions on either the researchers or their methodology, and yet I can’t help but worry about reports of this kind. Huge data bases are tempting geologies for data mining. But association is not necessarily causation.

As the humorist James Thurber once wrote: ‘Well, if I called the wrong number, why did you answer the phone?’ –just in case, I guess…


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