Cerebellar volumes were measured on structural MRI at adolescence and adulthood in 65 preterm individuals (born before 33 weeks’ gestation), and a term-born comparison group, in a study at King’s College, Great Ormond Street Hospital, and University College, London; and Seoul National University College of Medicine, Korea. Cerebellar volumes in late adolescence and adulthood (mean age 18.6;SD=1.02) were 3.11% and significantly smaller than measurements during early adolescence (mean age 15 years;SD=1.43) in the preterm group (P=0.000), whereas cerebellar volumes increased 0.44%, but did not change significantly with age in the control group (P=0.612). The changes in cerebellar volume correlated with tests of behavior and cognitive function. High General Health Questionnaire (GHQ)-12 scores, a self-reporting wellbeing test (eg feeling worthless, poor concentration), indicative of increased risk of mental health problems, correlated with reduction in cerebellar volume during late adolescence and young adulthood. Cerebellar volume correlated positively with full scale, verbal and performance IQ in early adolescence in the very preterm group but not the term-born group. Correlations with IQ were not maintained after controlling for white matter volume. 
COMMENT. A decrease in cerebellar volume occurring between mean age 15 years and 18.6 years in very preterm individuals is correlated with impaired feelings of wellbeing, but a correlation with IQ deficits is not significant when controlled for white matter volume. These findings corroborate previous reports of cerebellar involvement in cognitive and neurobehavioral disorders.