Findings suggest that although there were no significant differences in amygdala volumes between groups, familial factors influence amygdala volumes. Discrepancies between studies measuring amygdala volume in MDD may be due to differences in amygdala boundary definitions.

Objective: We examined the etiology of two disordered eating characteristics.Method: Participants included 1,470 female adolescent and young adult twins and their female nontwin siblings. Phenotypic factor analyses of a seven-item eating pathology screening tool yielded two factors: weight and shape concerns and behaviors (WSCB) and binge eating (BE). Univariate and bivariate extended twin analyses (including cotwins and nontwin siblings) were used to estimate the magnitude of genetic and environmental influences on these characteristics.Results: Analyses indicated that individual differences in WSCB and BE could be explained by additive genetic influences (a 2 5 0.43 (95% CI: 0.33-0.52) and 0.49 (95% CI: 0.36-0.58), respectively), with the remaining variance due to nonshared environmental influences. The genetic correlation between WSCB and BE was estimated at 0.64; the nonshared environmental correlation was estimated at 0.27. Discussion: These results corroborate previous findings on genetic and environmental influences on disordered eating characteristics and suggest that findings can be extended to nontwin populations.

The lack of significant differences across birth periods suggests that season of birth effects may not generalize to general disordered eating characteristics in nonclinical samples.

Objectives: Previous studies have found a season of birth effect for women with eating disorders. However, findings regarding the two types of season of birth (i.e. month of birth and temperature at conception) have been conflicting, and few studies have examined relationships between season of birth and general disordered eating in non-clinical populations. The present study sought to examine this relationship more closely by investigating both month of birth and temperature at conception in undergraduate women. Method: Subjects included 427 undergraduate females from a large university in the United States. Disordered eating in the areas of body dissatisfaction, compensatory behaviour, binge eating and weight preoccupation was assessed with the Minnesota Eating Behaviors Survey (MEBS). Results: No significant mean differences in MEBS scores were found between those individuals born in the first versus second half of the year. Furthermore, no significant associations were found between disordered eating and temperature at conception. Discussion: Our findings suggest that disordered eating symptoms do not show a season of birth effect. Discrepancies between these findings and those for clinical samples suggest the possible presence of different aetiological mechanisms for general eating symptoms versus clinical eating disorders.

No abstract