Objective: To determine pre-injury prevalence and post-injury incidence of DSM-III-R oppositional defiant disorder (ODD) and conduct disorder (CD), increase in disruptive symptoms after severe paediatric traumatic brain injury (TBI) and risk factors associated with development of these disturbances.

Methods: Ninety-four children were followed 1 one year after severe TBI. Assessments of pre-injury and 1-year psychiatric status were ascertained by parent report. The 1-year incidence of disruptive behaviour disorders/symptoms was the main outcome measure.

Results: The pre-injury prevalence of ODD and CD in the TBI sample was 6% and 8%, respectively, the prevalence of pre-injury CD being significantly higher than in a reference population. The incidence of new-onset ODD and CD 1-year post-injury was 9% and 8%, respectively, the incidence of new-onset CD being significantly higher than in a reference population. ODD symptoms and total number of disruptive symptoms increased significantly over the first post-injury year. Significant risk factors for disruptive disorders/symptoms included higher pre-injury psychosocial adversity, delinquency ratings and affective lability.

Conclusions: Pre-injury conduct disorder is a significant risk factor for post-injury disruptive behaviours. New-onset CD and disruptive symptoms are consequences of TBI at 1-year post-injury. Risk factors for these post-injury disturbances are similar to risk factors in non-TBI populations.