Assertiveness training was, for a stretch of the 1970s, one of the most heavily studied interventions in clinical psychology, then it largely fell out of fashion as the field moved toward other approaches. In a 2018 paper in the journal Clinical Psychology: Science and Practice, the psychologists Brittany Speed, Benjamin Goldstein and Marvin Goldfried revisited that older body of evidence and argued the field had dropped something that actually worked. Their review describes assertiveness, the capacity to state a preference, refuse a request, or express a need directly, as a factor connected to a wide range of clinical problems, and assertiveness training as what they call a genuinely transdiagnostic intervention, meaning it shows benefits across several different conditions rather than one narrow diagnosis.
This is one review of an older evidence base, not a single new experiment, and it does not settle exactly how large the effect is for any specific person. What it does establish is that the ability to hold a boundary, at least as psychologists have operationalized and measured it since the 1970s, is not simply a personality quirk. It is a skill that responds to training and that tracks measurably with other outcomes, including self-esteem.
What happens when boundary-setting is missing
A newer and more specific line of research helps explain why some people struggle to hold a boundary in the first place. In a 2025 paper in PsyCh Journal, the psychologist Xiaoxue Kuang and colleagues developed and tested a Chinese-language questionnaire measuring what they call people-pleasing, across a sample of 2,203 university students. Their questionnaire split the pattern into three parts: pleasing thoughts, such as automatically prioritizing what others want; pleasing behaviors, such as agreeing to requests one privately wants to refuse; and pleasing feelings, such as guilt or anxiety at the thought of disappointing someone.
The researchers found that higher scores across these three dimensions were consistently associated with worse mental health outcomes in their sample, including more neuroticism and lower self-worth. This is one study, in one cultural context, using one newly developed measure, so the specific numbers should not be treated as a universal formula. But the three-part structure the researchers describe, thought, behavior, and feeling, offers something more useful than a personality label: a description of what is actually happening in the moment someone fails to say no, not just a name for the pattern afterward.
Why this connects specifically to self-respect rather than confidence
It would be easy to read this research as simply saying confident people set better boundaries, but that oversimplifies what these studies actually describe. A boundary is not primarily an act of confidence. It is an act that depends on a person’s sense of worth holding steady even after they disappoint someone else, which is a narrower and more specific requirement than confidence in general. Someone can feel entirely sure of their abilities at work and still struggle to tell a family member no, because the two situations draw on different, more specific versions of self-regard.
This lines up with a broader distinction researchers have drawn between self-esteem that is stable and self-esteem that depends on specific outcomes, including how others respond to a given request. A person whose sense of worth depends heavily on being seen as agreeable or helpful has, in effect, a built-in cost every time they say no. A person whose sense of worth does not hinge on that particular approval has a much lower cost to pay for the same refusal. Read this way, “self-respect” is less a trait some people simply have and others lack, and more a description of how much a specific refusal is allowed to threaten someone’s overall sense of worth.
What the research says boundaries are not
None of this research treats a boundary as a synonym for being blunt, cold, or uncooperative, and the assertiveness training literature Speed and colleagues reviewed specifically distinguishes assertive communication from aggressive communication, describing assertiveness as stating a need clearly without either suppressing it or attacking the other person. The Kuang team’s questionnaire similarly does not treat every instance of accommodating someone else as unhealthy; it measures a persistent pattern of neglecting one’s own needs and feeling unable to do otherwise, not the ordinary, occasional choice to help a friend out.
What this looks like when it is working
Put together, these two bodies of research point toward a fairly concrete signature of a boundary that is coming from a stable sense of self-worth rather than a fragile one. The refusal is stated plainly, without an elaborate justification built to preempt the other person’s disappointment. It does not require repeated apologizing once it has been said. And critically, based on the pleasing-feelings dimension in the Kuang team’s questionnaire, it is not followed by a lingering surge of guilt that has to be managed afterward. That last piece is worth underlining, because a boundary that technically gets stated but leaves the person who stated it anxious for the rest of the day looks, on the surface, like assertiveness, while functioning, underneath, much more like the pattern the people-pleasing research describes.
None of this means the discomfort of disappointing someone should disappear entirely before a boundary counts as healthy. Both bodies of research describe a matter of degree, not an all-or-nothing switch: some contextual awareness of how a refusal lands for someone else is ordinary and not itself a sign of fragile self-worth. What the research points to is the difference between a brief, appropriate discomfort and a persistent, disproportionate one that shapes decisions well beyond the specific request being declined.
What this does not prove
The people-pleasing questionnaire study surveyed university students in China at a single point in time, which cannot establish that people-pleasing causes worse mental health rather than the reverse, that struggling mental health makes it harder to set boundaries in the first place. The assertiveness training review, meanwhile, draws on decades of older studies conducted under different research standards than are common today, and the authors themselves frame their paper as a call to revisit and modernize this evidence, not as a claim that the original findings are beyond question. Setting a boundary well is also not, on its own, a guarantee of anyone’s underlying well-being; it is one visible, measurable behavior that these two bodies of research link to how stable a person’s sense of self-worth is underneath it.
What is left, once the oversimplified version is set aside, is a modest but well-supported account: the difficulty many people feel when refusing a request is not primarily a communication problem to be solved with better phrasing. It is more often a sign of how much that specific refusal is being allowed to cost someone’s sense of their own worth, and that cost, the research suggests, is something that can genuinely change.