The study found that the children of aged parents had fewer externalising behaviour problems, as reported by the parents.
The study's authors noted that they focused only on children's externalising and internalising behaviour problems, so the findings cannot be generalised to other behaviours.
In childhood mental health problems are mainly of two types- Internalising problems (emotionally reactive, anxious, somatic complaints and withdrawn) and externalising problems (attention problems and aggressive behaviour).
 A detailed understanding through the early childhood years of internalising and externalising trajectories compared to the available norms could inform prevention initiatives for mental health.
Gender might also be relevant to agreement; one study found that parent teacher agreement was higher when rating kindergarten boys' externalising
problems than girls' (Gagnon, Vitaro & Tremblay, 1992).
Exploring and deciphering problems are a key theme in NT that refers to the process of externalising
. According to McLeod (2003:235), 'One of the distinctive features of narrative therapy is the procedure' referred to as 'externalising
Researchers from the Bradley Hasbro Children's Research Centre also found that teens with externalising
disorders (which includes attention deficit hyperactivity disorder, conduct disorders and angry, defiant or hostile behaviors like stealing) are more likely to be sexually active than their peers, putting them at higher risk for HIV and other STIs.
Within the study cohort, the prevalence of externalising
disorders was 13.8 percent and 11.1 percent for internalising disorders.
A foster parents' report of externalising
behaviour problems was expected to be a stronger predictor of disruption and negative outcomes than a caseworker's report.
In the model, exposure to sibling violence (perpetration and victimisation), child mental disorder and placement characteristics are risk factors for impaired psychological functioning (internalising and externalising
symptoms) and for disruptions in school competence (scholastic and social competence with classmates).