Are twins’ behavioural/emotional problems different from singletons’?

Abstract

We compared twins with singletons in the National Epidemiological Child Psychiatric Study, which included 122 twins and 5455 singletons, born in 1981 and selected at random. Behavioural and emotional symptoms were assessed in 1989 on the basis of questionnaires filled in by the parents (Rutter Parent Questionnaire) (RA2), teachers (Rutter Teacher Questionnaire) (RB2) and the children themselves (Children's Depression Inventory) (CDI). Parents' reported proportions of probable behavioural/emotional disorders did not differ between the twin and singleton girls, but among the twin boys there was a nonsignificant trend of being more often probably disturbed. Twins were reported to be less disturbed than singletons according to the teachers' assessments. No difference was found between twins and singletons in their self-reports. When analysing parents' reported values of various sum scores, the twin boys obtained slightly higher scores than singletons, while twin girls scored significantly lower on total and emotional disturbances. Twin boys obtained lower mean scores than singletons for probable disorder in the teachers' evaluations, the differences arising mostly in the emotional area. The same type of trend, however nonsignificant, was found among the teachers' evaluations of girls. No significant difference was found in the mean scores for hyperactivity. This large population-based sample suggests that twins may have a lower rate of behavioural problems in childhood than singletons, a finding that has to be taken into account in behavioural genetic studies.

Physical and mental decline and yet rather happy? A study of Danes aged 45 and older

“…Nevertheless, differences in well-being between twins and singletons were less than 0.05 SD and thus very small (Johnson, Krueger, Bouchard, & McGue, 2002). Furthermore, both lower suicide risk in twins and similarity in the self-report of depression have been found in other studies comparing twins and singletons (Moilanen et al, 1999; Tomassini, Juel, Holm, Skytthe, & Christensen, 2003). …”

Genetic and environmental contributions to the association between ADHD and affective problems in early childhood—A Swedish population‐based twin study

“…A further consideration regards the generalizability of results from twins to singletons. However, previous studies seem to indicate that twins and singletons are comparable with regard to ADHD symptoms and affective problems [Angold et al, 2002;Moilanen et al, 1999], indicating that it is possible to generalize our results from twins to singletons. Moreover, family studies have shown that relatives of individuals with ADHD have a higher risk of depression, and vice versa, indicating that our findings would likely extend to singletons [Faraone and Biederman, 1997], although these designs are not able to tease apart genetic and environmental influences.…”

Genetic relations between effortful and attentional control and symptoms of psychopathology in middle childhood

“…Angold, Erkanli, Silberg, Eaves, and Costello (2002) found no differences in depression scores for twins and single born children between the ages of 8 and 17, while Moilanen et al (1999) found nonsignificant trends suggesting lower rates of emotional and behavioral problems in twins. Studies with larger, population-based samples usually find no differences between twins and singletons in internalizing and externalizing (Lytton & Gallagher, 2002).…”