Early adversity linked to faster biological aging in teens via fear responses

When children grow up surrounded by danger, their bodies and brains appear to adapt in ways that can leave lasting fingerprints on their biology. A new study published in the Journal of Behavioral Medicine suggests that two fundamentally different kinds of childhood adversity—threat and deprivation—shape the developing fear system in strikingly different ways, with one dimension blurring the line between safety and danger while the other may actually sharpen it. The findings offer some of the most detailed evidence yet that the type of hardship a child experiences matters as much as how much of it they endure.

The research, led by Leah Cha of the University of California, Los Angeles, together with Craig K. Enders, Shiloh Cleveland, Katie A. McLaughlin of the University of Oregon, and Jennifer A. Sumner, examined 168 children and adolescents between the ages of 8 and 16 recruited from schools, after-school programs, medical clinics, food banks, and the broader Seattle community. Rather than treating adversity as a single undifferentiated burden, the team separated it into two dimensions that have become central to modern developmental science. Threat-related adversity encompasses experiences involving harm or the risk of harm, including physical abuse, sexual abuse, emotional abuse, and domestic violence. Deprivation-related adversity refers to the absence of expected inputs from the environment, such as emotional or physical neglect, food insecurity, and low cognitive stimulation. Youth and their caregivers both reported on lifetime experiences, and the researchers combined these accounts to construct continuous composites for each dimension.

The central question was whether these two dimensions of early life adversity relate differently to fear-related processes measured across multiple levels of analysis—neural, physiological, and subjective—and whether fear responses might explain why threat, in particular, has been linked to accelerated biological aging in young people. Prior work by the same team had shown that experiences of threat, but not deprivation, were associated with advanced pubertal development and advanced epigenetic age relative to chronological age in this cohort. Biological age, unlike chronological age, captures the pace of physiological development and decline, and accelerated biological aging is thought to be a key driver of age-related diseases such as cardiovascular disease and of heightened mortality risk.

To probe fear responding, the researchers used a fear conditioning and extinction task adapted and validated for children. In the task, images of blue and yellow bells served as conditioned stimuli: one bell signaled danger, because in 80 percent of its presentations it co-terminated with an aversive 96-decibel alarm, while the other bell signaled safety and was never paired with the alarm. The task unfolded in phases—preconditioning, conditioning, and extinction—allowing the team to track how children learned to distinguish danger from safety and how they updated that learning when the danger cue no longer predicted the alarm. Fear responses were captured in two ways during this task: skin conductance response, a well-established psychophysiological index of sympathetic arousal measured continuously through the fingertips, and self-reported fear ratings collected after each phase. In a separate functional magnetic resonance imaging session, participants viewed negative and neutral images while the researchers measured activation in the amygdala, the almond-shaped brain region central to detecting and responding to threat.

The results revealed a clear dissociation between the two adversity dimensions. Greater threat-related adversity was associated with impaired discrimination between the danger and safety cues during conditioning, as measured by self-reported fear—a finding that remained significant even after the researchers applied statistical correction for multiple comparisons. Youth with high levels of threat exposure showed the smallest gap in fear between the cue that predicted the alarm and the cue that predicted nothing, suggesting that their fear had generalized to cues that were actually safe. On the physiological side, threat also moderated skin conductance responses during early extinction, when neither cue was followed by the alarm. Strikingly, youth with the highest levels of threat exposure showed greater skin conductance to the safety cue than to the danger cue during this phase, a pattern consistent with difficulty updating threat associations when circumstances change.

Complementing these behavioral and physiological findings, threat-related adversity was associated with heightened activation of the left amygdala when youth viewed negative compared with neutral images. This association, too, survived correction for multiple comparisons. It extends earlier work in the same cohort showing that children with histories of maltreatment exhibit elevated left amygdala activation, and it does so using a continuous measure of threat while statistically accounting for co-occurring deprivation. Taken together, the authors argue, these converging patterns suggest that threat-related adversity may correspond to heightened neural sensitivity to negative stimuli alongside a reduced ability to distinguish danger from safety—a combination that could keep the fear system chronically engaged even under objectively safe conditions.

Perhaps the most unexpected result involved deprivation. Contrary to the prevailing expectation that deprivation-related adversity would show no relationship to fear learning, the researchers found that greater deprivation was associated with enhanced discrimination between danger and safety cues during the late phase of conditioning, based on skin conductance response. Youth with the highest levels of deprivation showed the largest differential response between the two bells, indicating more precise learning about which cue predicted danger. This pattern was specific to the physiological measure and did not extend to self-reported fear, hinting that the effects of deprivation may be more visible in the body’s automatic responses than in conscious experience. The authors interpret this finding through evolutionary-developmental frameworks such as the “hidden talents” model, which proposes that harsh and unpredictable early environments may compromise some cognitive skills while strengthening others. Attention regulation, which is critical to fear learning because it determines how strongly a cue becomes associated with an aversive outcome, may be one such strengthened capacity.

The theoretical backdrop for these divergent patterns comes from dimensional models of adversity advanced by McLaughlin, Sheridan, and colleagues. Threat-related adversity is theorized to selectively alter neural circuitry involved in detecting danger, fear learning, and emotion regulation—notably the amygdala and fronto-amygdala circuits—whereas deprivation is thought to affect the development of circuits supporting language, executive function, and the frontoparietal network. The new findings fit this framework: threat reshapes the machinery of fear itself, promoting rapid danger detection at the cost of safety discrimination, while deprivation appears to leave fear learning largely intact and may even refine cue learning under certain conditions.

The study also set out to answer a more ambitious question: whether fear-related responses could statistically explain the previously documented link between threat and accelerated biological aging. The researchers measured two aging metrics—Horvath epigenetic age, estimated from DNA methylation profiles at more than 850,000 sites across the genome using saliva samples, and self-reported pubertal stage using Tanner staging, both residualized on chronological age. Contrary to their hypotheses, the analyses revealed no significant indirect effects. Fear responses did not account for the connection between threat and accelerated aging, suggesting that other pathways—such as inflammation, neuroendocrine dysregulation, oxidative stress, sleep, diet, or social isolation—may be the more likely biological intermediaries linking early threat to faster aging.

The researchers are careful to note the limits of their evidence. Adversity was assessed retrospectively through youth and caregiver reports, which are vulnerable to underreporting; the composites did not capture the timing or duration of adversity; and the sample, drawn from a community with high representation of severe adversity—nearly half of participants had experienced physical abuse or domestic violence, and over 20 percent had experienced sexual abuse—may not generalize to lower-risk populations. Several findings, particularly those involving skin conductance and deprivation, did not survive false discovery rate correction, so replication is essential. The epigenetic clock used, while validated for saliva and for youth, was trained on chronological age rather than on disease and mortality outcomes, and pediatric-specific clocks may offer additional insight in future work.

Even with these caveats, the study represents a methodological advance. By modeling fear responses with multilevel techniques that track how learning at one phase shapes responding in later phases, and by examining the neural, physiological, and subjective levels simultaneously, the team moved beyond the single-measure snapshots that have characterized much of the prior literature and produced results that sometimes converge in ways single measures cannot. The finding that danger and fear can bleed into safety cues among youth exposed to threat is clinically resonant: overgeneralized fear and poor safety learning are hallmarks of anxiety and post-traumatic stress, and extinction learning is a core target of exposure-based therapies. Meanwhile, the possibility that deprivation may sharpen certain kinds of associative learning reframes adversity not solely as damage but as adaptation, opening the door to strengths-based approaches to prevention and intervention.

The broader message is one for scientists and clinicians alike: childhood adversity is not a monolith. The experiences that threaten a child’s safety and the experiences that deprive a child of expected care appear to sculpt the developing fear system in different directions—one heightening sensitivity to danger while eroding the capacity to recognize safety, the other possibly honing the ability to learn which is which. Understanding those differences, the authors argue, is essential for tailoring interventions to the diverse forms of adversity young people actually face, and for tracing the biological pathways through which early hardship becomes embodied as accelerated aging and disease.