Objective To report the parent-reported behavioural outcomes of infants included in the Systemic Hydrocortisone To Prevent Bronchopulmonary Dysplasia in preterm infants study at 2 years’ corrected age (CA).

Design Randomised placebo-controlled trial.

Setting Dutch and Belgian neonatal intensive care units.

Patients Infants born <30 weeks’ gestation and/or birth weight <1250 g, and ventilator dependent in the second week of life.

Intervention Infants were randomly assigned to a 22-day course of systemic hydrocortisone (cumulative dose 72.5 mg/kg; n=182) or placebo (n=190).

Main outcome measures Parent-reported behavioural outcomes at 2 years’ CA assessed with the Child Behavior Checklist (CBCL 1½−5).

Results Parents completed the CBCL of 183 (70% (183/262)) infants (hydrocortisone group, n=96; placebo group, n=87). Multiple imputation was used to account for missing data. Infants with critically elevated T-scores (>55) were found in 22.9%, 19.1% and 29.4% of infants for total, internalising and externalising problems, respectively; these scores were not significantly different between groups (mean difference −1.52 (95% CI −4.00 to 0.96), −2.40 (95% CI −4.99 to 0.20) and −0.81 (95% CI −3.40 to 1.77), respectively). In the subscales, we found a significantly lower T-score for anxiety problems in the hydrocortisone group (mean difference −1.26, 95% CI −2.41 to –0.12).

Conclusion This study found high rates of behaviour problems at 2 years’ CA following very preterm birth, but these problems were not associated with hydrocortisone treatment initiated between 7 and 14 days after birth in ventilated preterm infants.

Trial registration number NTR2768; EudraCT 2010-023777-19.