Comparison of the developmental trajectories of childhood internalising and externalising problems between children born in the late 20th century versus early 21st century in the UK

Children’s mental health is a significant public health concern. Internalising problems, such as anxiety and depression, are inward-directed difficulties that cause distress within the individual. Externalising problems, including conduct problems and hyperactivity, are externally directed difficulties that create conflict or distress in others. Parental mental health difficulties are a well-established risk factor for internalising and externalising problems in children. The negative consequences of these problems during childhood on later outcomes are well documented.

Research has documented generational differences in the prevalence of internalising and externalising problems among children and adolescents, with more recent cohorts showing higher levels compared to earlier cohorts. Despite this, few studies have examined how internalising trajectories have changed over time and none have explored changes over time in externalising trajectories.