Inter-twin Relationships and Mental Health

Abstract

W e evaluated dominance-submissiveness between cotwins and its relationship to mental health in a cohort study of 419 twins followed from pregnancy to 22-30 years of age. Dominance-submissiveness between co-twins was assessed from three separate perspectives: physical dominance, psychological dominance, and verbal dominance. Depressive, nervous, and psychosomatic symptoms were analyzed in different twin groups. In the physical domain, males were more commonly dominant than females at school age and in adulthood. Before and at school age, girls were more dominant than boys in the psychological and verbal domains, as well as in total dominance. These differences disappeared in adulthood, and 81% of adult twins felt themselves equal to their co-twin in total dominance. Submissiveness in the psychological domain seemed to be associated with increased depressiveness, nervous complaints and psychosomatic symptoms in males of male-female twin pairs. Verbally submissive males in same-sex twin pairs had more depression and psychosomatic symptoms. Among females of same-sex twin pairs, submissiveness in the psychological domain was most clearly associated with depressive symptoms, whereas psychological or verbal dominance-submissiveness among females from male-female twin pairs was not associated with symptoms. Psychologically dominant males and females of same-sex twin pairs expressed greater nervousness than did their co-twins. We conclude that being submissive, especially in the psychological domain, to a female twin partner seems to be stressful, whereas it is easier, especially for females, to be submissive to a male twin partner.

Depressive and Psychosomatic Symptoms in Twins With Special Reference to Co-Twin Dependence

“…It could be that being dependent on a female twin partner might protect from depressiveness. This situation concerning co-twin dependence appeared to be different from the situation of co-twin submissiveness to a twin sister, which was previously found to be stressful (Ebeling et al, 2003). Dependence on a twin partner thus may indicate a feeling of being well cared for by the twin sister (Bryan, 1992).…”

“…The twins have been followed at 10-year intervals: at 2-10 years, 12-20 years and now at 22-30 years of age. The data collection has been described in detail previously (Ebeling et al, 2003).…”

“…These analyses were performed separately in males and females. Moreover, as twinship has been suggested to constitute a different growing environment for same-sex (SS) and oppositesex (OS) twin pairs as well as for monozygotic (MZ) and dizygotic (DZ) twin pairs (Allen et al, 1976;Ebeling et al, 2003;Pulkkinen et al, 2003), we evaluated the differences in symptom reporting between different twin pairs and in different zygosity groups.…”

How Long Do the Consequences of Parental Preference Last: A Study of Twins From Pregnancy to Young Adulthood

“…The twins have been followed at 10-year intervals, at 2 to 10 years of age, 12 to 20 years of age and now at 22 to 30 years of age. The data collection has been described in detail previously (Ebeling et al, 2003).…”

Social Comparison Orientation in Monozygotic and Dizygotic Twins

“…Because MZ twins share nearly all their genes while DZ twins share on average 50% of their segregating genes, people expect MZ twins to be more similar than DZ twins for any trait that is influenced by genes. The label 'identical' when talking about MZ is a good illustration of this expectation that leads parents, other family members, teach-ers, and friends to compare the twins on various characteristics, such as height, weight, skills and abilities, and social behavior (Ebeling et al, 2003;Stewart, 2000). Although these pressures towards uniformity may encourage and even force the twins to compare with their co-twin, this comparison did not receive much attention in twin research.…”