Adolescence is a time of social and cognitive development associated with changes in brain structure and function. These developmental changes may show an altered path in individuals born before 33 weeks' gestation (very preterm; VPT). The cerebellum is affected by VPT birth, but no studies have yet assessed the adolescent development of this structure, or whether developmental changes in cerebellar structure are associated with cognitive and behavioural outcome. We measured cerebellar volumes on structural magnetic resonance images in 65 adolescents who were born before 33 weeks' gestation (VPT) and 34 term-born adolescents (mean age VPT = 15.09, SD = 1.43/mean age term-born = 15.43, SD = 0.56) and again in adulthood (mean age VPT = 18.61, SD = 1.02/mean age term-born = 19.17, SD = 0.95). Participants also underwent neuropsychological tests; the Wechsler Abbreviated Scale of Intelligence and the Controlled Oral Word Association Test and completed the General Health Questionnaire-12. Repeated measures ANOVA showed a main effect of time-point (F = 4.59, df = 1, P = 0.035) and a time-point by group interaction (F = 8.03, df = 1, P = 0.006) on cerebellar growth. By adulthood, cerebellar volumes were 3.11% smaller in the preterm group than they had been in early adolescence (P = 0.000). Cerebellar volume did not change significantly in the control group (P = 0.612). There were significant negative correlations between change in cerebellar volume and GHQ-12 in the VPT group; total score (r = -0.324 P = 0.028) and several subscales; concentration (r = -0.378 P = 0.010), feeling useful (r = -0.311 P = 0.035), decision-making capability (r = -0.348 P = 0.018), overcoming difficulties (r = -0.331 P = 0.025), feeling confident (r = -0.309 P = 0.037) and feeling worthless (r = -0.329 P = 0.026). In the VPT group there were positive correlations between cerebellar volume and full-scale IQ (adolescence; r = 0.471, P = 0.002/adulthood; r = 0.309, P = 0.047), performance IQ (adolescence; r = 0.434, P = 0.004/adulthood; r = 0.345, P = 0.025) and verbal IQ (adolescence; r = 0.401, P = 0.008) which were not maintained after controlling for white matter volume. We have demonstrated a reduction in cerebellar volume between adolescence and young adulthood in VPT individuals, which is correlated with reduced self-reported wellbeing.

The corpus callosum grows dramatically in VPT adolescents, and this growth is associated with neuropsychological outcome. This may represent a delay of a normal maturational process in VPT individuals.

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