Adolescent mental health is shaped by a constantly shifting conversation between biology and experience, according to a new study examining how genes and environments interact in the development of internalising and externalising psychopathology. Published in Translational Psychiatry, the research by A. Musial, A. G. Allegrini, R. Cheesman and colleagues focuses on two broad but clinically important patterns of behaviour. Internalising problems include symptoms such as anxiety, depression, social withdrawal and emotional distress, while externalising problems involve behaviours directed outward, including aggression, impulsivity, rule-breaking and substance-related risk. The study’s central message is that adolescent mental-health outcomes cannot be understood by looking at inherited vulnerability or environmental adversity in isolation.
The distinction between internalising and externalising psychopathology is widely used in developmental psychology because it captures two major pathways through which psychological difficulties appear. Internalising symptoms are often less visible to parents, teachers and health professionals, even when they severely affect sleep, concentration, relationships and academic performance. Externalising symptoms may attract attention sooner because they disrupt classrooms, families or peer groups. Yet the two domains frequently overlap. An adolescent experiencing chronic anxiety may become irritable and impulsive, while persistent conduct problems can be accompanied by depression, shame or emotional isolation. By examining both patterns together, the research addresses the possibility that apparently different disorders may share biological and environmental foundations.
Genes do not function as fixed instructions that determine a child’s future. Instead, genetic variation can influence sensitivity to stress, emotional regulation, reward processing, attention and social information. These influences are probabilistic: they may raise or lower the likelihood of a particular outcome without making that outcome inevitable. Environmental conditions, meanwhile, include far more than dramatic trauma. Family conflict, socioeconomic hardship, bullying, educational pressure, neighbourhood safety, digital experiences, friendship networks and access to supportive adults can all contribute to developmental trajectories. Gene–environment research investigates how these forces combine, asking whether genetic differences alter responses to experience and whether environments influence how biological predispositions are expressed.
One technical concept relevant to this field is gene–environment interaction, often abbreviated G×E. A statistical interaction occurs when the relationship between an environmental exposure and a mental-health outcome differs according to genetic liability, or when the influence of genetic liability changes across environmental conditions. For example, a stressful environment might be associated with a much stronger increase in symptoms among adolescents with one level of inherited sensitivity than among those with another. This does not mean that a single “risk gene” causes a disorder. Modern psychiatric genetics shows that mental-health traits are highly polygenic, meaning that thousands of genetic variants, each usually exerting a very small effect, contribute to susceptibility.
The study also speaks to the growing use of genetic indicators such as polygenic scores. These scores combine the effects of many DNA variants to estimate a person’s statistical liability for a trait identified in large genetic studies. They are not diagnostic tests and cannot predict an individual’s future with certainty. Their value in developmental research lies in helping scientists examine broad patterns across populations. When combined with detailed information about family life, peer relationships, education and other exposures, polygenic measures can help researchers test whether inherited vulnerability is amplified, buffered or redirected by the environments in which adolescents grow up.
A major challenge is separating genuine biological interplay from confounding factors. Families transmit both genes and environments, a phenomenon known as genetic nurture. Parents may pass on genetic tendencies associated with impulsivity or emotional sensitivity while also creating environments that reflect those tendencies. For instance, parental stress or behavioural difficulties can influence household routines and conflict, while inherited liability is simultaneously passed to the child. Researchers must also consider passive, evocative and active gene–environment correlation. Young people may inherit traits that lead them to seek particular settings, evoke specific responses from others or select experiences compatible with their temperament. These processes can make genes and environments appear intertwined even when they are not interacting in the strict statistical sense.
Adolescence is an especially important period for studying these relationships because it combines rapid biological, cognitive and social change. Puberty alters hormonal systems and brain networks involved in reward, threat detection and self-control. At the same time, peer approval becomes more influential, academic demands increase and young people begin making more independent decisions. Brain systems involved in motivation and emotional response mature at a different pace from systems supporting long-term planning and impulse control. This developmental imbalance does not doom adolescents to poor outcomes, but it can increase sensitivity to both harmful and protective experiences. Supportive relationships, stable routines and timely mental-health care may therefore have effects that differ across developmental stages.
The implications extend beyond the debate over nature versus nurture, a framework that scientists increasingly regard as too simplistic. If vulnerability is shaped through dynamic feedback between biology and experience, prevention should not be limited to identifying supposedly high-risk individuals. School-based emotional-skills programmes, anti-bullying interventions, family support, safer digital environments and accessible psychological treatment may reduce symptoms even when inherited liability is substantial. Conversely, genetic information must be handled with caution. Labelling a young person as genetically “at risk” could create stigma, affect expectations or divert attention from changeable environmental conditions. The most responsible interpretation is that genetic findings may eventually improve population-level understanding, not define an adolescent’s identity or destiny.
The findings and framework presented by Musial, Allegrini, Cheesman and colleagues reinforce a broader shift in psychiatric research toward developmentally informed, integrated models of mental health. Internalising and externalising symptoms are not simply isolated categories, and neither genes nor environments operate as independent causes. Their effects unfold across time, within families, schools and peer groups, and through biological systems that remain responsive to experience. Understanding these interactions could help explain why two adolescents exposed to similar adversity follow different paths, or why a modest change in support can have a major effect for one young person but not another. The research ultimately points toward a more precise and humane view of adolescent psychopathology—one in which vulnerability is real, but outcomes remain shaped by context and open to intervention.
Subject of Research: Gene–environment interplay in internalising and externalising psychopathology during adolescence
Article Title: Gene–environment interplay in internalising and externalising psychopathology in adolescence
Article References: Musial, A., Allegrini, A.G., Cheesman, R. et al. “Gene–environment interplay in internalising and externalising psychopathology in adolescence.” Translational Psychiatry (2026). https://doi.org/10.1038/s41398-026-04383-x
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41398-026-04383-x
Keywords: adolescence, adolescent mental health, gene–environment interaction, internalising psychopathology, externalising psychopathology, psychiatric genetics, developmental psychology, polygenic risk, mental-health research
