Adverse life circumstances in early childhood, such as poverty, homelessness, family conflict, parental separation, harsh parental discipline, parental mental illness, parental violence, or chronic illness in the family, can impact mental health throughout childhood, and this in turn has adverse consequences for the development of cognitive abilities at least up to age 14. These are the alarming conclusions of a new study from the University of Cambridge that offers fresh insights into how these known effects of early-life adversity interact and evolve over time.
"It is likely that the associations between early-life adversity, cognitive functioning and mental health arise, at least in part, due to developmental interactions,” the researchers said. Their study, published in the Journal of Child Psychology and Psychiatry, used data on 13,287 children in the ongoing prospective Millennium Cohort Study of children born in UK between 2000 and 2002.
The children were assessed on measures of early-life adversity (classified as taking place before age 3) and administered a variety of tests of mental health and cognitive functioning at ages 3, 5, 7, 11, and 14. Mental health was assessed by parent-completed scores on scales of emotional symptoms, peer problems, conduct problems, pro-social behaviour, and hyperactivity domains. Cognitive function was assessed by tests of spatial working memory at age 11 and vocabulary performance at age 14.
The researchers, from the MRC Cognition and Brain Sciences Unit at the University of Cambridge, used a statistical technique designed to tease out the extent to which mental health affects the relationship between early-life adversity and cognitive functioning later in childhood. They reported that early-life adversity at age 3 "strongly predicted poorer mental health" across all ages from 3-14 years.
'Developmentally Sensitive Time'
Although the association was strongest at age 3 and got progressively weaker over time, "this suggests that exposure to early-life adversity at this developmentally sensitive time has a negative long-term impact on mental health", the team said. They cited other research showing that this developmental period, characterised by rapid neuronal changes, may be particularly sensitive to environmental stressors, whereas after this it would require a more substantial exposure to stress to have similar impact on the neural system.
Early-life adversity also predicted cognitive functioning decrements over the course of childhood, based on poorer performance on tests of working memory at age 11 and of vocabulary at age 14.
Furthermore, analysis showed that most of the effects of early adversity on cognition were mediated by mental health changes. The impact on mental health resulting from early adversity accounted for 59% of the variance in poorer working memory performance at age 11, and explained 70% of poorer performance in vocabulary at age 14.
"The impact of adversity on cognition was partially due to its negative effects on mental health during development," said the authors. "In other words, children who experienced early-life adversity were most likely to experience mental health difficulties from age 3 to age 14, although poorer mental health was greater at age 3 than in the later years."
'Lasting Effects on Cognitive Performance'
"Early-life adversity can lead to prolonged periods of poor mental health, which in turn may have lasting effects on cognitive performance, such as working memory and vocabulary," said lead author Dr Tochukwu Nweze from the MRC Cognition and Brain Sciences Unit, recipient of a Cambridge Africa Scholarship, whose research explores the neural and cognitive developmental trajectories of individuals exposed to early psychosocial risks.
"Our findings not only highlight the deleterious effects of adversity on mental health and cognitive abilities but also reveal one of the mechanisms through which these effects manifest and persist over a long period of time," he explained. "Prolonged periods of poor mental health as a result of early-life adversity may have lasting or partially cumulative effects on cognitive abilities of working memory and vocabulary."
More sanguinely, the team also found that reductions in mental health difficulties over time were associated with improvements in working memory and vocabulary.
"This suggests that if behavioural and psychological difficulties can be addressed when children are young, the effects of early-life adversity on later cognition could be alleviated," the researchers said. "These findings have important potential clinical and educational implications, because they suggest that academic and cognitive resilience may be supported through early mental health interventions in vulnerable children."
Interventions Could Mitigate Effects of Early Adversity
They suggested that interventions should "focus on building resilience in children who have experienced early-life adversity", particularly at a time of "rising mental health challenges" among teenagers and young people.
Dr Nweze said: "We already know that poor mental health and cognition are associated with numerous behavioural problems which affect life quality and satisfaction. This reinforces the need for early interventions to give children the best possible life-outcomes.
"We suggest that educators in collaboration with clinicians could foster greater resilience by attempting to break this vicious cycle of persistent and self-sustaining mental health difficulties faced by individuals who experienced early adversity through some sort of deliberate and targeted clinical intervention."
Asked to comment by Medscape News UK, George Hosking OBE, founder of the WAVE Trust, which campaigns to reduce the impact of adverse childhood experiences on children's physical health, mental health, and life chances, said: "The research does not surprise us, and reinforces multiple previous studies with similar findings."
The research was funded by Cambridge Trust under the Cambridge African Scholarship scheme.