Children who spend time in a neonatal intensive care unit (NICU) at birth have a higher risk of mental health issues later


Children who spend time in a neonatal intensive care unit (NICU) at birth have a higher risk of mental health issues later, regardless of their birth weight, say McMaster University researchers.

The study examined the mental health of NICU graduates in childhood (four to 11 years) and adolescence (12 to 17 years), using data from parent and youth psychiatric interviews.

The research builds on previous studies that suggest extremely low birth weight babies who are admitted to the NICU are more likely to develop mental health issues during those years.

The results were published in Archives of Disease in Childhood.

“Advancements in the medical care of patients admitted to the NICU have led to improved outcomes for infants and families, and the need for NICUs has increased in Canada and the U.S.,” said study senior author Ryan Van Lieshout, associate professor of psychiatry and behavioural neurosciences at McMaster.

“However, little has been known about the mental health of the broader population of NICU graduates, particularly as they enter late childhood and adolescence.”

The study used a provincially representative cohort from the 2014 Ontario Child Health Study, led at McMaster. Parents provided data on psychiatric disorders for 3,141 children aged four to 11 and in 2,379 adolescents aged 12 to 17. Additionally, 2,235 adolescents aged 12 to 17 completed the interview themselves

Children aged four to 11 who had a NICU admission were nearly twice as likely to have any mental disorder or have more than one mental illness. The risk of separation anxiety disorder, specific phobia, attention deficit hyperactivity disorder, or oppositional defiant disorder also increased.

At the age of 12 to 17 years, NICU graduates remained at nearly twice the risk for developing any psychiatric problem, multiple psychiatric problems and oppositional defiant disorder as reported by adolescents and their parents.

Van Lieshout added that additional research and more data are needed to better understand potential causal factors, and further identify at-risk individuals.

“Existing follow-up guidelines of preterm infants suggest monitoring for mental health issues, and this study provides preliminary evidence that in the future it may be prudent to expand this to all infants who stay in a NICU regardless of birth weight status,” said Van Lieshout.

Van Lieshout added that additional research and more data are needed to better understand potential causal factors, and further identify at-risk individuals.

Funding: The study was funded by the Canadian Institutes of Health Research; Ontario Ministry of Health and Long-Term Care; Ontario Ministry of Children and Youth Services, and Ontario Ministry of Education.

While preterm infants now have high rates of survival,1 they continue to experience significant neurodevelopmental impairments linked to preterm birth.

Even ‘mature’ preterm infants born at 28–36 weeks’ gestation have significantly higher rates of behavioural, cognitive and psychiatric deficits compared with term-born peers.2–7 

Beyond neurodevelopmental abnormalities, children born preterm demonstrate elevated rates of lung disease8 9 and maladaptive growth.10 11 ‘Prematurity’, however, is not uniformly predictive or well-understood in the causal pathway of morbidity.

The heightened risk of lifelong multisystem dysfunction associated with prematurity is only partially explained by severity of illness in infancy.9–15 

In fact, traditional perinatal risk factors—gestational age (GA), for example—have little prognostic value.16 

Although children born at the limits of viability or who suffer severe neonatal illness often have predictably poor outcome, the aetiology of significant deficits seen in the large population of moderately preterm infants with benign medical history remains poorly understood.

Alterations in developmental trajectory, rather than focal end organ injury following preterm birth, are implicated.6 17

Early-life environmental exposures can alter developmental trajectories in critical and often unexpected ways to produce clinically important outcomes years later.

Numerous prospective birth cohorts, often drawn from communities with high pollutant burden, have used maternal biomarkers as estimates of fetal exposure to explore the influence of the third trimester environment on long-term child health outcomes.

Third trimester fetal life, a critical period for brain and lung development as well as for metabolic programming, is now known to be particularly sensitive to environmental perturbations.

Whether the normal developmental trajectory is impacted by environmental toxicants in the neonatal intensive care unit (NICU) has not been rigorously studied.

In addition to providing life-sustaining treatments, the NICU confers significant exposure to chemical plasticisers, heavy metals, potentially toxic stress, social isolation and other environmental factors shown to be detrimental to brain development in studies of term-born fetuses and infants.18–

21 We believe that opportunities exist to improve outcomes of preterm infants by optimising the NICU from an environmental health perspective.

Cohort description

The NICU Hospital Exposures and Long-Term Health (NICU-HEALTH) longitudinal preterm birth cohort is based in the premise that modifiable environmental exposures in the NICU contribute to developmental deficits in children born preterm.

The NICU-HEALTH infrastructure facilitates detailed study of the NICU exposome and comprehensive assessment of early developmental progress, allowing us to measure the impact of modifiable environmental exposures during the preterm period on multisystem outcomes.

McMaster University


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