Foster care affects nearly every dimension of a child’s development, from brain structure and emotional regulation to school performance and long-term physical health. About 368,500 children were in the U.S. foster care system at the end of 2022, and the developmental challenges they face stem from a combination of early adversity before placement and the disruptions of the foster care experience itself. The good news: many of these effects can be buffered or reversed when children land in stable, supportive placements early on.
Changes in Brain Structure
The stress of early neglect, abuse, and separation from caregivers leaves measurable traces in the developing brain. Brain imaging studies show that children raised in institutional or out-of-home care have smaller volumes of both white and gray matter compared to children raised at home. Specific reductions appear in the prefrontal areas responsible for decision-making, impulse control, and reading social cues, with lower blood flow and thinner tissue in those regions. The corpus callosum, the bundle of fibers connecting the brain’s two hemispheres, consistently shows reduced volume and structural integrity in these children.
These aren’t abstract findings. A smaller, less connected prefrontal cortex makes it harder for a child to manage emotions, plan ahead, and respond flexibly to new situations. It helps explain why foster children often struggle with behaviors that adults interpret as defiance or inattention, when the underlying issue is that the brain’s self-regulation system developed under chronic stress.
Emotional Development and Attachment
Forming a secure bond with a caregiver is the foundation of healthy emotional development. Children who enter foster care have often experienced broken or harmful attachments, and the process of being removed from a home, however unsafe, can compound that damage. About 5% of children show signs of Reactive Attachment Disorder (RAD) at the time of their initial placement, a condition marked by difficulty forming emotional connections and unusual social behavior. After at least a year in improved care conditions, that rate drops to roughly 2%, suggesting that a stable, responsive caregiver relationship can begin to repair attachment difficulties even after a rocky start.
Beyond the clinical diagnosis, a broader range of children in care show insecure attachment patterns: difficulty trusting adults, fear of abandonment, trouble identifying or expressing their emotions, or a tendency to either withdraw from relationships or cling to them anxiously. These patterns often follow children into adolescence and adulthood, shaping how they form friendships, romantic partnerships, and eventually parent their own children.
Cognitive and Language Delays
About 40% of toddlers in foster care score in the below-average or very low range for general cognitive ability. In the general population, that figure is roughly 16%. Preschool-aged children in care show delays in language, visual-spatial reasoning, and overall cognitive functioning compared to age-matched peers.
These gaps don’t necessarily reflect a child’s innate potential. Early deprivation, inconsistent stimulation, and the chaos of multiple placements can all stall cognitive growth. A child who has moved homes three times by age four may have had three different sets of routines, three different communication styles, and no consistent adult narrating their world in a way that builds vocabulary and reasoning skills. With stable placement and targeted support, many of these children make significant gains, but the window for early intervention matters enormously.
Academic Achievement and School Barriers
The cognitive delays carry forward into the classroom. High school dropout rates for youth in foster care are three times higher than average, and only about 55% graduate from high school compared to 86% of the general population. The barriers are stacked: each time a child changes placements, they often change schools, losing credits, relationships with teachers, and continuity in their learning. Absenteeism, suspensions, and unmet special education needs are all more common among foster youth. Many lack a consistent adult advocate who can push back when schools fail to provide accommodations or properly transfer records.
School instability is especially damaging. A child who switches schools mid-year doesn’t just lose a few weeks of instruction. They lose their peer group, their sense of belonging, and often the one teacher who understood their situation. For a child already primed to distrust adults, starting over in a new classroom can feel like confirmation that no relationship is permanent.
How Placement Stability Shapes Behavior
The number of times a child moves between homes is one of the strongest predictors of behavioral problems in foster care. Children with unstable placements have roughly twice the odds of developing behavioral issues compared to children who achieve early stability. Among lower-risk children, the probability of behavioral problems was 22% for those who stabilized early, versus 36% for those who didn’t. That’s a 63% increase in behavioral difficulties attributable to instability alone, not to the child’s background or temperament.
Even among children who entered care with high baseline risk (more trauma, more complex needs), early stability made a meaningful difference. In this group, 47% of children who stabilized early showed behavioral problems, compared to 64% of those with unstable placements. The pattern held across every risk level: regardless of what a child had been through before entering care, placement instability added a 36% to 63% increase in the likelihood of behavioral difficulties.
Kinship Care Makes a Difference
Where a child is placed matters as much as how often they move. Children placed with relatives (kinship care) consistently show better behavioral outcomes than those placed with unrelated foster families. Three years after placement, an estimated 32% of children in early kinship care had behavioral problems, compared to 46% of those in traditional foster care. This gap persisted even after accounting for the fact that children in kinship placements tended to be lower-risk at baseline and experienced fewer moves.
The reasons are intuitive. A grandparent or aunt already shares the child’s history, culture, and family identity. The child doesn’t have to learn an entirely new household’s rules, foods, and rhythms. They’re more likely to maintain contact with siblings and other relatives. Kinship care also tends to be more stable: children placed with relatives are less likely to experience the disruptive cycle of moving from home to home.
Physical Health Into Adulthood
The effects of foster care don’t stop at emotional or cognitive development. Adults who spent time in foster care as children have higher rates of chronic health conditions than both economically advantaged peers and peers from similarly disadvantaged backgrounds who were not placed in care. Asthma rates are roughly four to five times higher among former foster youth. Hypertension rates are about four times higher. Average BMI is also elevated, with the foster care group showing the highest body mass index of any comparison group studied.
Chronic stress in childhood triggers sustained inflammatory responses that, over years, increase vulnerability to metabolic and cardiovascular problems. Combined with the inconsistent healthcare, poor nutrition, and limited health education that many foster youth experience, these biological changes translate into real health disparities by the mid-twenties.
Aging Out of the System
Youth who leave foster care at 18 without being adopted or reunified face especially steep odds. Between 31% and 46% of young people who age out of the system experience at least one episode of homelessness by age 26. This isn’t simply a matter of not finishing school or not finding work. Research from a large Midwest study found no clear relationship between the risk of homelessness and a young person’s education or employment status, suggesting that the lack of a family safety net, someone to call when rent is short or a lease falls through, plays a central role.
The transition hits so hard because most 18-year-olds, even those with stable families, aren’t ready to manage housing, finances, and healthcare independently. Foster youth are expected to do all of that without the informal support network that most young adults rely on well into their twenties.
What Builds Resilience
Despite these risks, many children in foster care develop remarkable resilience. The strongest protective factor, consistently, is a stable and supportive relationship with a caregiver. When trauma-affected children develop strengths in their relationships, they show greater adaptation: fewer behavioral needs and fewer mental health challenges. Family functioning, both within the foster home and in maintaining connections to the child’s broader network, is the single most important factor in building that resilience.
Research increasingly supports an asset-based approach to working with foster children, one that identifies and builds on a child’s existing strengths rather than focusing exclusively on diagnoses and deficits. In studies grouping foster children by their profiles of needs and strengths, the largest group was consistently a “resilient” group characterized by a high percentage of personal strengths and minimal actionable needs. Their primary area for support was family functioning, reinforcing the idea that the quality of the caregiving environment is the lever that matters most. For children in care, the relationship is the intervention.