Same Family. Same Stress. Different Child.
The developmental science behind why children respond differently to the same stress
Two siblings. Same family. Same divorce, same cross-country move, same parent deployed, same hard season.
One becomes quieter. Withdrawn. Tearful in ways that are hard to name. The other gets louder — more defiant, more explosive, harder to reach.
Same stress. Different child.
If you’ve ever watched this happen in your own home, you’re asking one of developmental science’s most important questions: Why does the same adversity produce such different outcomes?
The answer has everything to do with something researchers call regulation pathways.
Research Spotlight
Before the science, two terms worth knowing:
Internalizing: distress that turns inward
Anxiety, sadness, worry, withdrawal
The child who seems fine at school but cries at bedtime
Stomachaches before hard days, going quiet when overwhelmed
Externalizing: distress that moves outward
Irritability, aggression, defiance, risk-taking
The child who picks fights, pushes limits, seems to be looking for a reaction
Big emotions that land on everyone around them
Neither is a character flaw. Both are ways a developing nervous system responds to stress.
And here’s what research increasingly shows: adversity doesn’t produce one outcome. It produces different outcomes depending on the child, the type of adversity, and the world surrounding them.
Lee et al. (2025) conducted a meta-analysis, which synthesized 127 studies and over 163,000 children. They found that the type of adversity matters in important ways. Researchers distinguished between:
Threat: experiences of harm or danger (abuse, violence in the home or community)
Deprivation: the absence of expected care or stimulation (neglect, emotional unavailability, food insecurity)
Both create risk, but they don’t create the same risk. Threat-based adversity had stronger associations with emotional and fear-based problems. Deprivation more specifically disrupted cognitive development, which over time shaped different patterns of behavioral difficulty. Same broad category of “hard childhood.” Meaningfully different developmental fingerprints.
Bista et al. (2025) made this concrete by tracking over 2,300 children from age 5 through age 17 using data from the Raine Study. Researchers mapped actual developmental trajectories and found five distinct patterns:
29%: consistently low problems across both dimensions
26.5%: primarily externalizing problems, low internalizing
17.5%: primarily internalizing problems, low externalizing
17%: both internalizing and externalizing co-occurring at high levels
10%: very high externalizing and high internalizing combined
Crucially, different combinations of individual, family, and maternal risk factors predicted each trajectory. The same broad category of family adversity didn’t uniformly push children in the same direction. That’s multifinality in action (this is the idea that one risk can branch into genuinely different developmental paths; aka multiple outcomes).
And the above data make that visible: even in the same population, followed from the same starting point, children sorted into five meaningfully different trajectories. That’s not randomness. That’s development doing exactly what it does.
Which brings us to context. A recent longitudinal study following nearly 10,000 children from ages 8 to 17 (Ferschmann et al., 2026) found that biological timing, specifically, when and how fast puberty unfolds, created real windows of vulnerability for both internalizing and externalizing problems. But when researchers accounted for the quality of children’s relationships (e.g., how openly they talked with parents, how satisfied they were in their friendships) those risks were largely absorbed. The biological risk was real but the relational buffer was more important.
Why This Matters
Parents often carry quiet versions of the same questions:
Why is one of my kids struggling more than the other?
Did I cause this?
Why are they reacting so differently when they went through the same thing?
The research doesn’t answer these with blame, so I hope we can stop the self-blame and parent-shaming that can occur with ‘misbehavior’. The science answers these questions with biology, context, and developmental nuance. Two children can go through the same experience and land in very different places not because one is weaker or more damaged, but because the type of stress, each child’s temperament, and the relationships available to them during that stress all interact in ways that are fundamentally individual.
The most actionable piece may also be the simplest. Children who talked openly with their parents, who shared what they were up to, who they were spending time with, and what was on their minds, showed fewer behavioral problems, even when biological risk was present. That openness doesn’t come from surveillance. It comes from a relationship warm enough that a child wants to share. And that relationship gets built in thousands of small, low-stakes moments long before the hard ones arrive.
You don’t have to be a perfect parent to be a buffering one. You just have to stay present long enough to be the person they talk to.
The Science Behind the Good Enough Parent
You’ve likely heard about Dr. Donald Winnicott’s concept of the “good enough” parent: a caregiver who doesn’t have to be perfect, just reliably attuned, especially when distress hits. Introduced in 1953, it was a radical shift from the dominant parenting advice of the late 1940s/early 1950s. What’s remarkable is that decades of research now show this im…
Long Story Short
Kids don’t experience stress the same way because development is not a formula and is not linear. The type of adversity matters, each child’s individual makeup matters, and the relationships surrounding them as they grow matter enormously. The same hard thing can look completely different in two different children — and that’s not a mystery or a failure. It’s development doing exactly what it does, one child at a time.
Quick Takeaways
Internalizing and externalizing are simply different ways kids respond to stress.
Not all adversity works the same way — experiences of threat (harm, danger) and deprivation (absence of care or warmth) shape development through different pathways
The same adversity can lead to very different outcomes depending on a child’s temperament, biology, and family context
Children in the same family can end up on completely different developmental trajectories.
Supportive relationships buffer biological and environmental risk.
Presence and openness are the intervention.
Development Decoded is built on a simple belief: science should be clear, practical, and accessible to anyone who cares about kids. I write, research, and create resources outside of my day job and family life to make that happen. If you’d like to help fuel the work, you can do so with one coffee at a time.
References
Bista, S., Tait, R. J., Straker, L. M., Lin, A., Steinbeck, K., Graham, P. L., Marino, J. L., & Skinner, S. R. (2025). Joint developmental trajectories of internalizing and externalizing problems from mid-childhood to late adolescence and childhood risk factors: Findings from a prospective pre-birth cohort. Development and Psychopathology, 37(1), 176–191.
Ferschmann, L., Dobbelaar, S., Tamnes, C. K., Tsotsi, S., Toenders, Y. J., & MacSweeney, N. (2026). Longitudinal associations between pubertal development and youth behavioral adjustment in the context of parent and peer relationships. Social Development, 35, e70068.
Lee, A. H., Kitagawa, Y., Mirhashem, R., Rodriguez, M., Hilerio, R., & Bernard, K. (2025). Do dimensions of childhood adversity differ in their direct associations with youth psychopathology? A meta-analysis. Development and Psychopathology, 37, 871–901.
Every child is genetically different at birth. Their temperament traits drive their first respond/reaction to change, new experiences, persistence, distractibility, activity, body clock, mood, and intensity as well as the way each of us collects data from our senses. It is measurable within the first few weeks after birth. The genes half from mom and half from dad drives our behavior and learning. It would be puzzling if they didn’t react differently. Expecting the environment to change our genes is like believing a certain parenting style can change eye color.