Perhaps it had something to do with living in a dark cupboard, but Harry had always been small and skinny for his age … [he] had a thin face, knobbly knees … and wore round glasses held together with a lot of Scotch tape because of all the times Dudley had punched him on the nose.

And so we are introduced to our protagonist, The Boy Who Lived, the Chosen One: Harry Potter. The seven books about the young wizard and his time at the Hogwarts School of Witchcraft and Wizardry have been translated into 73 different languages and sold over 450m copies worldwide. And readers wouldn’t guess, after author J K Rowling’s introduction of Harry, that the orphaned boy would be the one to defeat the powerful and devastating Dark Lord Voldemort.

Harry’s home life wasn’t as exciting as his rising wizardry: he was snubbed by his only remaining family, bullied by his cousin and classmates, and resided in that dark cupboard under the stairs. His uncle Vernon, aunt Petunia, and cousin Dudley Dursley – to whom he was passed as an infant after the death of his parents – ensure that he’s properly malnourished at all times. After spending a day cleaning the Dursley’s entire house and working outside in the blazing July heat (on his 12th birthday, no less), Aunt Petunia prepares for Harry “two slices of bread and a lump of cheese” before sending him off to hide during their dinner party with the Masons. It’s no wonder he was so small for his age.

But perhaps something other than the physical abuse stunted his growth, too. Beyond the malnourishment, it’s possible for children who go through experiences like Harry Potter to suffer from what is known as psychosocial short stature.

Psychosocial short stature (PSS) is a growth disorder caused by extreme stress and emotional deprivation endured during childhood. Symptoms, which typically appear after age two and continue into the early teenage years, include short stature, immature skeletal age, and improper body weight for the child’s height.

A persistently stressful environment ensures that the body is constantly in “fight-or-flight” mode. In the short-term, the adrenal glands respond to stress by releasing epinephrine (also known as adrenaline) and norepinephrine. These hormones cause dilation of muscle vasculature and increased heart and lung function, but inhibit unimportant processes like digestion.

But with long-term physical or psychological stress, the outer portion of the adrenal glands releases another hormone called cortisol. Rat pups deprived of their mother show significantly higher cortisol levels than pups that haven’t been. Cortisol inhibits the secretion of growth hormone from the pituitary gland in the brain, which we attribute widely to increasing height and bone mineralisation as children develop into teens and adults. Interestingly, kids with Cushing’s syndrome (characterised by abnormally high levels of cortisol) also tend to have short stature and lower bone density compared to their healthy peers.

Several studies on PSS have shown that when a child leaves an abusive home environment, growth hormone insufficiency can be reversed. In fact, kids and teens seem to undergo rapid “catch-up growth” to what is likely their genetically predetermined height.

Harry’s growth is noted over the course of the series. During the Battle of Hogwarts in the last book, Harry recalls the spirits of his parents and his father James is described as being “exactly the same height as Harry”. It seems he caught up after all.

Harry Potter was emotionally and psychologically deprived when he entered Hogwarts. To be fair, he was probably still the most stressed bloke in the series, what with Voldemort, death eaters, basilisks, dementors, Triwizard tournaments, and countless deaths of beloved friends. But at Hogwarts, he also experienced, for the first time ever, trusting friendships, being part of a sports team, the strong bond of family, and discovered true love. And with that he flourished – not just emotionally, but physically. The unlimited food available in the Great Hall probably helped, too.