Rather than a list of forbidden phrases, the research points to two things parents are wiser not to say as a habit: personal put-downs, which warmth does not cancel out, and the message that love has to be earned

Articles about what parents should never say tend to arrive as a list of banned phrases, which is both intimidating and not very useful, since no parent gets through childhood without a sentence they wish they could take back. The research is more forgiving and more precise than a list of forbidden words. It does not identify magic phrases that wound. It identifies two broad patterns that, repeated over time, are linked to worse outcomes, and it says something reassuring about everything else.

We are writers, not clinicians, and what follows is a reading of the research, not psychological advice. It is also worth saying at the outset that nearly every parent does versions of these things occasionally. The evidence is about habits and severity, not about a single hard day.

With that in mind, the first pattern is the one most people would guess, though the detail that comes with it is not.

Personal put-downs, and why warmth does not cancel them

The clearest evidence concerns what researchers call harsh verbal discipline: not ordinary firmness or the occasional raised voice, but shouting and screaming, cursing at a child, and insults that attack the child rather than the behavior, calling them stupid, lazy, or worse. In a longitudinal study of 967 two-parent families published in Child Development in 2013, Ming-Te Wang and Sarah Kenny found that parents who used this kind of discipline when their child was 13 had children with more depressive symptoms and more conduct problems a year later, things like lying, stealing, and trouble at school.

The finding that makes this worth reporting is a second one. The researchers tested whether a warm, close parent-child relationship softened the damage, on the theory that a teenager would absorb the harsh words as coming from love. It did not. Parental warmth did not lessen the effect, leading Wang to conclude that harsh verbal discipline appeared detrimental across the board. The common reassurance, they know I love me really, so it is fine, is exactly the belief the data did not support. Contempt aimed at the child does not seem to be neutralized by affection elsewhere.

This is one study, not the final word, and it has a complication built in. The relationship ran both ways: children with conduct problems at 13 drew more harsh discipline from their parents over the following year. So this is a cycle, parent and child feeding each other, rather than a simple story of blame. But the direction from harsh words to worse outcomes was real, and it is why the put-down, as a repeated habit, is the first thing the evidence flags.

The quieter pattern: love that has to be earned

The second pattern is subtler, and many parents who would never dream of insulting a child use it without noticing. Psychologists call it parental conditional regard, and it means making affection and approval visibly contingent on the child behaving or achieving as the parent wants. It shows up less in insults than in warmth that switches off. The cold shoulder after a bad grade. The pointed I am so disappointed in you. The sense, conveyed over time, that a good child is loved and a disappointing one is quietly withdrawn from.

Research by Avi Assor, Guy Roth, Edward Deci and colleagues found that this approach has a catch. Conditional regard often works in the narrow sense, it secures the behavior the parent wanted, which is why it is so tempting and so common. But it came with costs. Children who felt their parents’ love was conditional reported more resentment toward those parents, and a more fragile, fluctuating sense of self-worth that swung between feeling on top and feeling ashamed. Their good behavior was driven less by their own values than by an internal pressure to keep earning approval. In their work, conditional regard buys compliance while quietly undermining a child’s secure sense of their own worth.

Put plainly, the message worth avoiding is not any single sentence but the accumulated impression that love is a reward for performance. That impression can be built without a single harsh word.

What this does not mean

It would be easy to read all this as a demand for perfect, scripted parenting, which is neither realistic nor what the research supports. A few qualifications keep it honest.

These are studies of patterns across groups, much of the evidence is correlational or based on self-report, and the harsh-discipline work came from a specific sample of two-parent, mostly middle-class families, so none of it delivers a verdict on any individual home. Setting firm limits is not harsh discipline, and expecting good behavior is not conditional love. The line the evidence draws is between disciplining the behavior and attacking the person, and between guiding a child and rationing affection according to their output.

It is also worth remembering that raising your voice once, or saying something you regret, is not what these studies measured. Nearly all parents do that. What seems to matter is the repeated pattern, and, crucially, what happens afterward. Circling back, acknowledging that you snapped, and reconnecting is not a sign that the damage is done. That repair is itself part of how secure relationships work, and it is available after almost every bad moment.

If any of this describes a cycle that feels stuck, or if a parent is worried about a child’s mood or behavior, a family doctor, a child psychologist, or an evidence-based parenting program is a better resource than an article, and reaching for that kind of help is a normal thing to do rather than an admission of failure.

The useful version of what parents should never say, then, is short and unfrightening. It is not a list of trapdoor phrases. It is two habits to lean away from: attacking who the child is rather than what they did, and letting your warmth become something they have to earn. Almost everything else, including a great many imperfect sentences, is the ordinary noise of family life, and the research suggests children are built to withstand it.