Is early potty training dangerous? What is the evidence base for delayed versus early potty training?

This post looks at both sides of the debate, including the evidence in support of early potty training as well as the reported dangers, and the idea of ‘readiness’.  It finds that the suggested “dangers” surrounding psychological risk and the development of voiding problems are unfounded in the available research, and concludes that supporting children to develop ‘readiness’ skills should start no later than 12 months, using a gentle, non-coercive approach.
(Find out how with my Baby Pottying Guide .)

It argues that our notions of when to start potty training are much more to do with parental readiness than that of a child’s maturation, and suggests that helping your baby use a potty from birth, leading to gentle, non-coercive potty training from around 18 months, is the best way to meet a child’s developmental needs both physically and psychologically.

what is Early potty training?

What we understand as ‘early’ as well as ‘training’ differs between cultures and approaches. Many people in North America and Europe would define early as before age 3, but in literature it’s generally deemed to be before 2 and very early if initiated before 18 months.

In terms of training, this depends on what the expectations are of the process and outcome. In the conventional sense, it means teaching a child to use a potty or toilet rather than a nappy (diaper) and thereby eliminating the need for nappies thereon. As Kachmar highlights, many potty training “experts” or advisors propose that children cannot achieve this until 18 months¹ and to do it earlier is not only futile, but potentially harmful (more on this in a moment). However, the practise of helping a  young baby use a potty (what we know as “elimination communication”) can often mean that babies have developed a capacity to be reliably clean and dry much earlier than this. These babies have not necessarily been “trained” in the way we have come to expect.

Many parents who practice “elimination communication” would disagree with the idea of it being described as potty training. Perhaps because the idea of training doesn’t seem so baby-led. Andrea Olson (Go Diaper Free) explains that “teaching can begin from birth, and this is very different from training” and describes what she calls “teaching some building blocks” as a critical component of preparing for later independence.²

In this post, I will describe early as anything before age 2.5, which is now generally considered the average age of initiating potty training in the UK.

Is your child over 18m? Start potty training today with my potty training eLearning which will show you step by step how to do it gently, swiftly and have you done with nappies for good!

POTTY TRAINING in other countries

In North America and Europe, parents generally wait until children are at least 2 years old before starting potty training. However, in 75 countries around the world, it is common for babies to use NO NAPPIES. ³ Half the world’s babies NEVER rely on nappies and are potty trained by 12 months of age. ⁴ In various countries around the world, babies are trained anytime from 2-24 months.⁶In Thailand, 92% of babies start potty training between 4-12 months old. ⁷ In Vietnam, babies are trained by 2 years old.⁸

why delay? THE “WAIT FOR READINESS” APPROACH

The “readiness” approach was introduced in the 1960s and remains widely accepted and popular today. Its fundamental premise is that there is an optimum point at which to begin toilet training, based on a child’s willingness to co-operate and engage with the process of developing toileting autonomy. Waiting until a child has developed a certain set of physical and cognitive skills will, it proposes, reduce the risk of unwarranted physiological or psychological damage.

Brazelton published the first paper recommending the approach, advocating for potty training from 18 months. He acknowledged that sphincter control could be developed by 9m of age and suggested that the optimum time to start potty training was from 18 months.

limitations of the readiness approach

The main piece of research supporting Brazelton’s potty training recommendations was based on a small, relatively homogeneous population, with no control group and performed only once in the 1960s. Since then, there has been very few studies assessing the efficacy of the method, with the first ever systematic review of toilet training strategies for healthy children finding just 6 related studies.

Despite the lack of rigorous evidence available into the outcomes of delayed potty training, I would argue that the fundamental ideas around the “readiness” approach are based on a pretty sound knowledge of child development. Where I believe many parents have been misled surrounds the idea that readiness can only be elicited from a certain age.

The conclusions of the available research in support of delayed potty training really show that approaches to potty training are more to do with parents’ assumptions about their child’s psychological development than about the exact time at which a child should begin.⁹

As Kachmar (2018) argues, if you look closely at the Brazelton technique, you will see that nearly all of the steps in the process are in fact initiated by parents, not children¹⁰.  This would appear to support the notion of parent-led potty training from a very young age. Perhaps ‘readiness’ has less to do with what babies are capable of, and more to do with adult attitudes towards engaging their babies with the process of learning toileting skills? Does delaying the onset of potty training disrespect our children’s own developmental capabilities? Are our efforts to avoid over-burdening young children with the task of toileting actually taking away important opportunities to develop readiness skills?

Developmental readines: is this age dependent?

Wu (2012) shows that if we break down the 28 separate toilet-readiness signs proposed by “readiness” methods, half of these signs occur between 12-24 months of age. However, if the requisite skills of independence have been removed, they can be observed as young as 9 months. Wu (2012) concludes that based on signs of readiness, “a reasonable approach would be for parents to consider toilet training when their child is able to communicate the need to urinate and is able to stay dry during a nap, or for 2 h during the day.”¹¹ In my experience (and that of many other parents who practise infant toileting), babies clearly communicate the need to eliminate from birth, and can develop the ability to stay dry for 2 hours from around 6 months if they are regularly encouraged to void in a potty rather than a nappy.

Jamie Glowacki, author of “Oh Crap! Potty Training” (2015) suggests these signs of readiness which may or may not correlate to a particular age:

• Has the child learned things by repetition and consistency?
• Can the child communicate needs such as hunger and thirst?
• Can the child throw a tantrum? (i.e. they are aware of their desires)

If we broaden our understanding of readiness beyond a child reaching an age where they can do things independently (as per the standard recommendations), we are likely to see our children as “ready” sooner.

Becoming “ready”

Imagine that you are teaching your child to ride a bike. Would you buy them a child-sized bike? Would you teach them about safety? Would you give them plenty of chance to practise in accordance with their developmental level? Or would you simply wait till they were old enough to acknowledge these things for themselves before you even introduced the concepts? Like many approaches to skill acquisition, I think you’d be more likely to start as soon as you saw an opportunity, recognising there is a journey of skill development involved before independence can be readily and gently achieved.  So in relation to helping children succeed with independent toileting, there is surely a similar trajectory in terms of preparation?

IS EARLY Potty training possible?

An international study by Rugolotto et al. of nearly 300 caregivers who helped their infants use a potty demonstrated that it was possible to recognise a baby’s cues and offer a potty.¹² Furthermore, It is possible to replicate the approaches used by non-westernised cultures, as demonstrated by Smeets et al (1985) in her observations of 3-7m infants in the Netherlands.¹³ You can read more detail on the available scientific literature in support of potty training in other cultures here. 

Did you know you can start baby pottying anytime? That you can do it part time and still use nappies until you are ready to potty train? You can apply gentle pottying principles and learning for potty training at any age even if you never offered your baby a potty before.  Find out how.

WHY WORRY ABOUT IT?

So many times I hear parents say or write “let them be babies”, or” they will do it when they are ready” or “we don’t need to push them”. And I agree with all these principles. However, in the context of potty training, I believe they are unfounded.

Kate Clanchy summarises why we have a duty to worry:

“I can’t help it: I do worry. I worry about the mound of 5,000 non-biodegradable disposable nappies sitting behind each unworried, non-anal western baby and the 70 cubic metre pond of water, and the hillock of 1,422kg of raw materials that were used to make them, and the vast 75,000 hectare estate required to grow those materials. To say nothing of his carbon footprint, and the slightly smaller carbon footprint of the few – perhaps rather more worried – western babies in washable nappies, especially if their mothers are guilty of using the tumble dryer, as I am.

“I am not disgusted by children’s shit so much as by our process of wrapping it first in a nappy, then in a scented plastic bag, then in the bin, then in landfill – nappies are 11% of domestic landfill – a mummified morsel that will outlast the pyramids.”¹⁴

Difficult to argue with that isn’t it? I’m not trying to make you feel guilty, but I do think we have a collective responsibility to leave a better world behind for the future. If parents simply started potty training sooner, we’d instantly reduce the environmental impact by half. Even if you’re reading this having already completed potty training (yey!), it’s never too late to pass this message onto those with babies still to reach this milestone.

start early

The practice of helping a young baby use a potty (elimination communication), has been shown to have various benefits, particularly relating to aiding complete bladder and bowel voiding.¹⁵Guerra et al (2014) found that bladder control is not merely a reflex, but a series of coordinated messages between the brain and the bladder designed to assist effective voiding.¹⁶Arguably, this supports the evidence that regular potty use maintains and develops sphincter control from a very young age.¹⁷

I believe that when babies are given regular opportunity to void in something other than a nappy, instead of teaching them to ignore their instincts and bodily signals, we help them to maintain their awareness which not only respects their innate capabilities but gently leads to readiness for potty training much sooner.

IS Early potty training physically “dangerous”?

Articles by  Dr Steve Hodges often do the rounds and are, from what I have found, the most commonly cited articles in support of delaying potty training for medical reasons. The dangers, he argues, concern the effects of urine and stool “holding”, resulting in decreased bladder capacity and constipation. He proposes that this is more prevalent amongst children who potty trainer earlier, but what he actually describes is not related to the timing of potty training but instead to stool and urine retention:

“To understand the risks of early training, it’s important to know that virtually all toileting problems – pee and poop accidents, bedwetting, urinary frequency, and urinary tract infections – are related to chronically holding pee or poop or both”¹⁸

We should not dismiss the importance of preventing dysfunctional voiding, but the relationship between early potty training and the development of problems later on is unfounded in the research evidence. Rather, as Kachmar (2018) notes, studies have shown that early potty training develops good bladder co-ordination¹⁹, reduces the incidence of urinary tract infections²⁰ and bladder accidents ²¹, promotes daytime dryness²²and actively protects the bladder.²³

Earlier potty training is also shown to reduce the incidence of toileting resistance ²⁴or stool toileting refusal which requires medical resolution²⁵.Late training, on the other hand, has been shown to result in more daytime wetting relapses and incontinence, and a longer duration of toilet training²⁶.

whats wrong with dr hodges?

Whilst he may suggest the development of voiding problems is related to ‘early’ potty training, this idea is anecdotal at best, and does not acknowledge any of the available clinical evidence that disputes it, such as this study which demonstrated no relationship between age of toilet training and voiding issues.²⁷ As Domanmum.com describes:

“The only thing that is damaging is chronic holding, which as this study mentioned, is not more likely to happen in earlier potty learners. Bladder problems such as infections and incontinence are actually more common in later potty learners (here, here, here, and others). The evidence says exactly the opposite of what he is claiming”²⁸.

There is another fundamental flaw in all of his research:  it is based on his knowledge of children who have urinary and bowel problems, not normal healthy children. So can his research be generalised to larger, healthier populations?

A friend of mine recently contacted Dr Hodges, asking him about patients he had seen in his clinic who had practised elimination communication (pottying from birth). In it he says:

“We’ve seen some EC patients, but we have a low prevalence in this area. We are generally opposed to early training for the reasons described on our website, but as long as the children empty well, there shouldn’t be an issue. (Making sure they empty well is the trick). [We see] more problems with the children trained 12-18 month […] very few actually practice elimination communication.”

Wait? So it’s actually all to do with effective voiding than the timing of potty training? Well, this is very convenient for parents to help their baby go potty, as research has shown that using a squatting position (as practised by parents using this method) aids complete voiding.²⁹

All children are at risk of developing constipation and urinary problems. And as serious as that is, I  believe there is no evidence base to relate it to the timing of potty training. As Jenn Philpott of Born Ready explains, don’t let the headlines mislead you – they may suggest early potty training is bad, but they don’t actually represent the research itself, which  concludes that constipation, rather than the age at which a child potty trains, is the cause of problems. The fact is that the age of potty training has risen, so has the incidence of urinary and bowel dysfunction.

the method, or the age?

What if we consider what humans did for 100,000’s of years before nappies were invented? If the suggestion is that potty training prior to 18 months is damaging, would that not mean that you, your parents, grandparents, and basically all generations before you, not to mention the 75 countries in the world who routinely use no nappies at all, are all psychologically damaged? Dr Hodges conveniently dismisses this idea, blaming it instead on diet and access to toileting facilities. Again, these suggestions are more to do with avoiding chronic constipation and urine holding than the age at which potty training is initiated. In fact, both these dangers can be avoided by gentle non-coercive potty training at an age when there is least likely to be resistance (i.e. before 24 months). 

I believe the available research suggests that our concerns over potty training are more to do with the method used, rather than the age at which potty training is initiated³⁰ If we are rigid with our babies, use harsh or punitive methods of toilet training, or shame them about their bodily functions, these are the things that can create problems. In particular, the way we speak to our babies about their eliminations risks stool toileting refusal (and therefore “holding”).³¹

Changes in potty training practices have been less driven by scientific data than by popular ideas of whether permissive or strict parenting was better.³² Parentingscience.com gives a good overview of the arguments for and against early potty training, and concludes “there is no evidence that early potty training harms children”.   Rather, such ideas are based on opinion rather than rigorous scientific research. They come down to a gross misrepresentation in the media fuelled by multi-million dollar investment in promoting disposable nappies. I would argue that the real danger lies in waiting too long (but that, of course, would sell fewer diapers, wouldn’t it?).

a gentle method to learn ‘readiness’

I firmly believe that a gentle, baby-responsive approach is completely beneficial and in-line with modern notions of attachment and intuitive parenting. For example, does this child look like she is being harmed by using a potty? Did she develop voiding problems later on (no), did my little boy, who was potty trained at 18m? (no), does the experience of  99% of the worlds children throughout history who potty trained before 3 years of age demonstrate what Dr Hodges describes? (no!):

So why has the average age of potty training risen and continued to rise?

Consider this:

“Have you considered whether or not your previous or current potty training views might be shaped by the disposable diaper industry? Would the realisation that you and other parents are being somewhat influenced by powerful for profit industry rather than scientifically-grounded, sound medical advice change your opinions?”(Kachmar, Maria, 2018, Lose the Diapers!).

Could it be that it was Brazelton’s significant conflict of interests, being employed as he was by Pampers to promote ever-larger sizes of nappies, which actually promoted delayed commencement of potty training? I’d agree it was a significant factor. In 1977, before disposables were popular, most North American and European children were trained around 9-11 months old.³³

A study cited by Kachmar (2018) by Largo and Stutzle in 1977 confirmed that the introduction of disposable nappies and media campaigns were the main contributors of delayed potty training. The promotion of a convenient single-use product that reduces or eliminates laundry and the required parent-led potty training approach has provided many parents with a justification to delay. I wouldn’t go so far as to say they were lazy, although this has been suggested. On the whole, I’d suggest it’s because many parents struggle to perceive a benefit in starting early. Furthermore, they are not aware of the potential pitfalls of delaying, particularly in relation to the development of healthy voiding capacity?

What do UK health officials say?

Visit the NHS website advice for potty training and you will find that it concludes there is “no perfect time” to train. Likewise, the Institute of Health Visitors says there is “no set time to start the process” but that “18m is a good time to start”. Importantly,  both officials recommend encouraging the development of “readiness skills”, something I would argue is absolutely intrinsic to helping a young baby use a potty instead of a nappy, from both a physical and psychological perspective.

Parentingscience.com argues that “passive waiting does nothing to help your baby “get ready“. There will always need to be some element of teaching to the process which is parent, not child, led. We can either teach our babies to use a nappy, or we can teach them that wearing a portable toilet is not the only choice. Find out how with my baby pottying eGuide.

TAKE HOME MESSAGES

Potty training should be gentle and non-coercive, respecting the development of independence at the child’s own pace. But this does not actually inform when to start, only how to approach it when we do.

We should not confuse elimination communication with potty training – the two are very different.

The research suggesting early potty training is dangerous is scientifically unfounded. The real danger lies in delaying potty training and thereby increasing the risk of developing voiding disorders.

Our notions of when to start potty training have got MUCH more to do with parental readiness than that of a child’s maturation.

The research underpinning the “wait for readiness” approach originally recommended initiating potty training from 12 months. However, the study did not consider non-verbal signs or the experience of parents who practise elimination communication that demonstrate that infants show signs of readiness from birth.

Helping your baby use a potty from birth, leading to gentle, non-coercive potty training from around 18 months, is a perfect way to meet a child’s developmental needs both physically and psychologically.

Thank you to other experts cited in this article for their research and writing into Elimination Communication and Potty Training, in particular Andrea Olson of Go Diaper Free and Maria Kachmar (Lose the Diapers!), for supporting this piece.

SUPPORT

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Here at Little Bunny Bear, we believe in sharing advice that is supported by research evidence, rather than anecdotal. Here are the links to the research evidence which supports this blog.

Research links

Azrin, N. H., Sneed, T. J., & Foxx, R. M. (1974). Dry bed: Rapid elimination of childhood enuresis. Behavioral Research and Therapy, 12, 147-156.

Bader Abramovitch, I., & Abramovitch, H. H. (1988). Enuresis in cross-cultural perspective: A comparison of training for elimination control in three Israeli ethnic groups. The Journal of Social Psychology, 129(1), 47-56.

Baeyens , D., Roeyers , H., Hoebeke , P., Verte , S., Van Hoecke, E., & Walle , J. V. (2004). Attention deficit/hyperactivity disorder in children with nocturnal enuresis. Journal of Urology, 171(6), 2576-2579.

Bakker, E., van Sprundel, M., van der Auwera, J. C., van Gool, J. D., & Wyndaele, J. J. (2001). Voiding habits and wetting in a population of 4332 Belgian schoolchildren aged between 10 and 14 years. Scandinavian Journal of Urology and Nephrology, 36, 354-362.

Banerjee, S., Srivastav, A., & Palan, B. M. (1993). Hypnosis and self-hypnosis in the management of nocturnal enuresis: a comparative study with imipramine therapy. American Journal of Clinical Hypnosis, 36(2), 113-119.

Berk, L. B., & Friman, P. C. (1990). Epidemiologic aspects of toilet training. Clinical Pediatrics, 29(5), 278-282.

Butler, R., Brewin, C., & Forsythe, I. (1990). Relapse in children treated for nocturnal enuresis: Prediction of relapse using pre-treatment variables. Behavioral Psychotherapy, 18, 65-72.

Byrd, R. S., & Weitzman, M. (1996). Bed-wetting in US children: Epidemiology and related behavioral problems. Pediatrics, 98(3), 414-419.

DeVries, M. W., & DeVries, M. R. (1977). The cultural relativity of toilet readiness: A perspective from East Africa. Pediatrics, 60(2), 170-177.

Graham, P. (1986). Child psychology. A developmental approach. Oxford, England: Oxford University Press

Liebert, R. M., & Fischel, J. E. (1990). The elimination disorders. In M. Lewis & S.M. Miller (Eds.), Handbook of developmental psychology (pp. 421-440). New York, NY: Plenum Press.

Norgaard, J. P., van Gool, J. D., Hjalmas, K., & Djurhuus, J. C. (1998). Standardization and definition in lower urinary tract dysfunction in children. International Children’s Continence Society. British Journal of Urology, 81(3), 1-16.

Oppel, W. C., Harper, P. a., & Rider, R. V. (1968). The age of attaining bladder control. Pediatrics, 42(4), 614-626.

Salkind, N. J. (2002). Child development. New York, NY: Macmillan References USA.

Schum, T. R., Kolb , T. M., McAuliffe, T. L., Simms, M. D., Underhill , R. L., & Lewis , M. (2002). Sequential acquisition of toilet-training skills: a descriptive study of gender and age differences in normal children. Pediatrics, 109(3), E48.

Vander Zanden, J. W. (2000). Human development(7th ed.). Boston, MA: Mc Graw Hill.

von Gontard, A. (1998). Annotation: Day and night wetting in children – A pediatrics and child psychiatric perspective. Journal of Child Psychology and Psychiatry, 39(4), 439-451.

von Gontard, A., Mauer-Mucke, K., Plueck, J., Berner, W., & Lehmkuhl, G. (1999b). Clinical behavioral problems in day-and night-wetting children. Pediatric Nephrology, 13, 662-667.

Zigler, E. F., & Finn-Stevenson, M. (1993). Children in a changing world. Development and social issues. Pacific Grove, CA: Brooks/Cole Publishing.

1. Maria Kachmar, 2018, Lose The Diapers: The No Fuss Potty Training Alternative https://www.amazon.com/Lose-Diapers
2. Go Diaper Free 5th Anniversary edition, 2018
3. Mann, D (2005) Potty Training Before Age 2: Elimination Communication
4. http://www.contemporarypediatrics.com/urology/toilet-training-getting-it-right-first-time; Sears, J https://www.thedoctorstv.com/articles/441-china-s-potty-training-secret
6.  In the Ukraine, 40% of babies begin toilet training between 6-8 months, and most are done training by 12m ⁵http://ukrsbaby.ru/rizne/poradi/32698-desjatij-misjac-zhittja-ditini.html
7. Benjasuwantep, 2011 /https://www.ncbi.nlm.nih.gov/pubmed/22295729
8. Duong et al (2012)  J Pediatr Urol. 2013 Dec;9(6 Pt A):808-14.
9. Thank you to Maria Kachmar (Lose The Diapers: The No Fuss Potty Training Alternative) for the citation to this piece of evidence. Christie, A. et al. (2010) Toilet training of infants and children in Australia: 2010 parental attitudes and practices. LLB (UNSW) , MPA (U Syd), M Env Law (USyd)
10. Maria Kachmar, 2018, Lose The Diapers: The No Fuss Potty Training Alternative https://www.amazon.com/Lose-Diapers-Potty-Training-Alternative/dp/1986143643/
11. Wu, His-Yang (2012) Pediatric Urology Review Can evidence-based medicine change toilet-training practice?
12. S. Rugolotto, M. Sun, L. Boucke, D.G. Calo, I. Tato. Toilet training started during the first year of life: a report on elimination signals, stool toileting refusal and completion age. Min Pediatrica, 60 (2007), pp. 27-35
13.  P.M. Smeets, G.E. Lancioni, T.S. Ball, D.S. Oliva. Shaping self-initiated toileting in infants. J Appl Behav Anal, 18 (1985), pp. 303-308.
14. https://www.theguardian.com/family/story/0,,1944603,00.html
15. Jordan, GJ, Elimination Communication as colic therapy (2014) Journal Med Hypotheses Sep;83(3):282-5. Bauer, I. Diaper free: the gentle wisdom of natural infant hygiene, Natural Wisdom Press (2001), L. Boucke, Infant potty training: a gentle and primeval method adapted to modern living,  White-Boucke Publishing (2008), C. Gross-Loh, The diaper free baby William Morrow Paperbacks (2007)
16. Luis Guerra, Michael Leonard, Marco Castagnetti (2017) Best Practice in the assessment of bladder function in infants,Therap Ad. Ur Volume: 6 issue: 4, page(s): 148-164
17. Benjasuwantep B, Ruangdaraganon N.(2011) Infant toilet training in Thailand: Starting and Completing Age and Factors Determining Them. J Med Assoc Thai. 2011 Dec;94(12):1441-6.Thank you to Kachmar, M (2018) whose book on Early Potty Training led me to find some of the articles referenced here. You can read more on the scientific evidence in favour of earlier potty training in her book Lose The Diapers! Maria Kachmar, 2018, Lose The Diapers: The No Fuss Potty Training Approach https://www.amazon.com/Lose-Diapers-Potty-Training-Alternative/dp/1986143643
18. https://www.babble.com/toddler/dangers-potty-training-early/
19. Neveus and Sillen (2013) Lower urinary tract function in childhood; normal development and common functional disturbances. Acta Physiol 207: 85–92 [PubMed]
20. Christie, A. (2010)http://web.maths.unsw.edu.au/~jim/annachristierpt10.pdf
21. Duong et al (2012) Urinary bladder control during the first 3 years of life in healthy children in Vietnam – a comparison study with Sweedish children. J Pediatric Urology 9(6) Pt A: 700-6
22. Yang et al (2011)Early Initiation of Toilet Training for urine was associated with early urinary continence and does not appear to  be associated with bladder dysfunction. Neurolosol Urodyn, 30:1253-7, 34(2) 203-203
23. Bakker E et al (2002) Results of a questionnaire evaluating the effects of different methods of toilet training on achieving bladder control. BJU International. 90, 456- 461. 
24. Sears (1957) Patterns of Childrearing. Evanston, iii. Row, Peterson and Company
25. Tautman et al. (2003) Stool Toileting Refusal: A prospective intervention Targeting parental Behaviours. Arch Pediat Adolescent med, 157(12) 1193-1196 / Issenman (1999) A Review of Bowel and Bladder Control Development in Children: How Gastrointestinal and Urologic Conditions Relate to Problems in Toilet Training. pediatrics
26. Joinson (2009),A prospective study of age at initiation of toilet training and subsequent daytime bladder control in school-age children.J Dev Behav Pediatr. Oct;30(5):385-93.
27. http://Pediatrics. 2003 Apr;111(4 Pt 1):810-4. Relationship between age at initiation of toilet training and duration of training: a prospective study. Blum NJ1, Taubman B, Nemeth N.
28. https://domanmom.com/responding-to-dr-hodge-dangers-of-potty-before-three/
29. https://www.ncbi.nlm.nih.gov/pubmed/12870773
30. D.M. Mota, A.J.D. Barros. Toilet training methods, parental expectations and associated dysfunctions J Pediatr (Rio J), 84 (2008), pp. 9-17
31. Taubman et al. (2003) Children who Hide While Defecating Before They Have Competed Toilet Training: A Prospective Study. Arch Pediatric: Adolescent Med 157(12)L 1190-1192
32. Pediatric Urology Review Can evidence-based medicine change toilet-training practice?
33. R. Sears, Robert & E. Maccoby, Eleanor & Levin, Harry. (1960). Patterns of Child Rearing. The American Journal of Psychology. 73. 10.2307/1419138