The science of toilet training: What research tells us about timing

© 2007-2010 Gwen Dewar, all rights reserved

When is the best time to begin toilet training? Infancy? 18 months? 24 months? Or even later?

There is surprisingly little research addressing this question. As I note elsewhere, opens in a new window each age is associated with its own costs and benefits.

But it’s fair to make a two general points.

1. The widespread belief that early potty training causes psychological or behavioral problems is not supported by the evidence. As I note below, this idea seems to have arisen because people conflated early training with bad training.

2. Kids who are trained late — i.e., after 32 months — might be at greater risk for developing bladder problems.

For the details, read on.

20th century attitudes about early potty training

Some parents today worry that early toilet training is harmful to children. As I will argue below, the scientific evidence doesn’t back it up. But where did the idea come from in the first place?

Early potty training got a bad reputation because it was once associated with bad training methods.

In the 1920s and 1930s, parents were urged to impose a rigid toilet training regimen on children before they could walk. Techniques were coercive, even abusive.

One government manual instructed parents to enforce “absolute regularity” of bowel movements by inserting a soap stick in the infant’s rectum at precise times of the day (United States Department of Labor 1935).

Other prevalent tactics included scolding and physical punishments for accidents (Hushka 1942; Stendler 1950; Luxem and Christophersen 1994.)

After World War II, the medical establishment began to reject early potty training.

Freudians claimed that early, rigid training caused emotional problems and neuroses later in life.

Pediatricians, like Benjamin Spock and T. Berry Brazelton, argued that pushing children may cause a variety of troubles, including stool withholding, stool toileting refusal, regression, and  opens in a new windowbedwetting (Leiberman 1972; Brazelton 1962; Brazelton and Sparrow 2004).

Child development researchers argued that training should not begin until kids could actively cooperate with the process (Brazelton et al 1999). Strict timetables for training were abandoned. Instead, parents were encouraged to let their children’s spontaneous curiosity set the pace.

These changes probably saved many children from harsh training methods.

But reformers seem to have confused methods with timing.

In one historical study I’ve read, the author clearly stated that that any training before 10 months is, by definition, coercive (Hushka 1942).

The important point is that “when to train” and “how to train” are different questions. Bad training methods can cause problems.

But does early timing cause problems? Based on modern studies, the answer appears to be “no.”

Science doesn’t support the idea that early training is harmful

The few scientific studies of  opens in a new windowinfant toilet training have reported no negative side effects (Ball 1971; Cederblad 1970; Smeets et al 1985). These studies focused only on basic skills and did not track children over the long-term. But the cross-cultural evidence suggests that long-term toilet training problems are rare (Ainsworth 1967; deVries and deVries 1977).

The evidence for toddler training tells a similar tale. Earlier training is not associated with behavioral problems.

For example, a U.S. study tracked over 400 children to learn what, if any, effects timing has on toilet training success (Blum et al 2003).

Children were enrolled in the study at 17-19 months. Their parents were interviewed every 2-3 months until they completed daytime potty training. Researchers compared children who began “intensive” training — defined as being asked to use a potty chair or toilet more than three times a day — before 27 months with those who began intensive training after 27 months.

The earlier starters were no more likely than later starters to experience constipation, stool toileting refusal, stool withholding, or hiding from parents (Blum et al 2003).

The only negative finding was that children trained earlier tended to take longer to complete training. Kids who starting training between 18-24 months took, on average, 13-14 months. Kids who trained after 27 months took 10 months or less (Blum et al 2003).

The authors infer from this result that there is “little benefit” in beginning potty training  between 18 and 27 months (Blum 2003).

However, the study directed parents to use a gradual, child-oriented approach to potty training. As a result, the younger participants might have been less prepared for training, which would have slowed their progress. If parents had been instructed to actively prepare their children for training, the results might have differed.

Moreover, the study by Bloom and colleagues didn’t address training before 18 months. When infant training is the goal, children may finish within 5-9 months (Smeets et al 1985; Boucke 2003).

There is evidence that delayed training could put children at risk for developing bladder problems

A case control study interviewed the parents of older kids (aged 4 – 12) who had been diagnosed with daytime incontinence (Barone et al 2009). These kids still had trouble suppressing the urge to urinate. Was there anything in their toilet training history that stood out?

When the kids were compared with a control group, researchers found that the incontinent kids were more likely to have begun toileting training after 32 months.

Previous studies have also reported links between late training and bladder trouble.

Belgian researchers interviewed the parents of kids in grade school and middle school (Bakker et al 2002a, Bakker et al 2002b).

They found that school-age kids with bladder problems — like daytime accidents, bedwetting, and recurrent urinary tract infections — were more likely to have started toilet training at a later age.

These results should be interpreted with caution. The case control study doesn’t tell us much about causation. And the Belgian study depended on parents’ recall many years after the fact.

Maybe some toddlers possess traits that make their parents delay training–and perhaps these same traits lead to more bladder problems later in life.

Maybe, too, parents with symptom-free children are more likely to minimize the effort of toilet training and to forget how early the process began.

But it makes sense that earlier training could reduce the incidence of urinary tract infections.

Toilet training helps children learn to completely empty their bladders—-an ability that reduces the risk of infection (Janson et al 2000; Sillen and Hanson 2000).

As a result, some researchers recommend that children with dysfunctional bladders should start training early (Hellstrom and Sillen 2001).

As for Freud, it’s interesting to note that Freud never singled out early training as the cause of personality disorders. He was concerned about any approach to training that might be regarded as extreme—too early, too late, too strict, too “libidinous” (Fenichel 1945, p. 305).

In any case, I can find no scientific studies that link the timing of toilet training with the  later development of emotional disorders. Freud identified certain personality types that have been confirmed by modern scientific studies. However, these personality types have NOT been linked to childhood toilet training experiences (Fisher and Greenberg 1977; Masling 1999).

More information

For more information, be sure to check out my article on  opens in a new windowchoosing the right potty training age, as well as these  opens in a new windowevidence-based potty training tips.

References: The science of toilet training

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Content of “The Science of toilet training: What research tells us about timing” last updated 4/10