Small for gestational age and poor fluid intelligence in childhood predict externalizing behaviors among young adults born at extremely low birth weight

Although infants born at extremely low birth weight (ELBW; birth weight < 1000 g) are at increased risk for developing later psychopathology, the mechanisms contributing to this association are largely unknown. In the present study, we examined a putative cognitive link to psychopathology in a cohort of ELBW survivors. These individuals were followed up prospectively at age 8 and again at ages 22-26. At 8 years, participants completed measures of fluid and general intelligence. As young adults, a subset of ELBW survivors free of major neurosensory impairments provided self-reports of personality characteristics related to psychopathology. Data from 66 participants indicated that, as predicted, the association between ELBW and externalizing behaviors was moderated by fluid intelligence. Specifically, ELBW individuals with poor fluid intelligence who were born small for gestational age (birth weight < 10th percentile for gestational age) showed the highest level of externalizing behaviors. These findings provide support for a cumulative risk model and suggest that fluid intelligence might be a cognitive mechanism contributing to the development of psychopathology among nonimpaired individuals who were born at ELBW and small for gestational age.