Towards further understanding of the co-morbidity between attention deficit hyperactivity disorder and bipolar disorder: a MRI study of brain volumes.

BACKGROUND: Although attention deficit hyperactivity disorder (ADHD) and bipolar disorder (BPD) co-occur frequently and represent a particularly morbid clinical form of both disorders, neuroimaging research addressing this co-morbidity is scarce. Our aim was to evaluate the morphometric magnetic resonance imaging (MRI) underpinnings of the co-morbidity of ADHD with BPD, testing the hypothesis that subjects with this co-morbidity would have neuroanatomical correlates of both disorders. METHOD: Morphometric MRI findings were compared between 31 adults with ADHD and BPD and with those of 18 with BPD, 26 with ADHD, and 23 healthy controls. The volumes (cm(3)) of our regions of interest (ROIs) were estimated as a function of ADHD status, BPD status, age, sex, and omnibus brain volume using linear regression models. RESULTS: When BPD was associated with a significantly smaller orbital prefrontal cortex and larger right thalamus, this pattern was found in co-morbid subjects with ADHD plus BPD. Likewise, when ADHD was associated with significantly less neocortical gray matter, less overall frontal lobe and superior prefrontal cortex volumes, a smaller right anterior cingulate cortex and less cerebellar gray matter, so did co-morbid ADHD plus BPD subjects. CONCLUSIONS: Our results support the hypothesis that ADHD and BPD independently contribute to volumetric alterations of selective and distinct brain structures. In the co-morbid state of ADHD plus BPD, the profile of brain volumetric abnormalities consists of structures that are altered in both disorders individually. Attention to co-morbidity is necessary to help clarify the heterogeneous neuroanatomy of both BPD and ADHD.

A twin study of alexithymia.

BACKGROUND: Factors contributing to the development of alexithymia and the nature of alexithymia's relation with trait negative and positive affectivity are unclear. In this study, a twin approach was used to examine the degree of genetic and environmental contributions to the different facets of alexithymia, and the nature of their relations to trait negative and positive affectivity. METHOD: Forty-five monozygotic and 32 same-sex dizygotic twin pairs completed the Toronto Alexithymia Scale-20, the Eysenck Personality Inventory, and a zygosity questionnaire. RESULTS: Model fitting analyses indicated that familial influences contributed significantly to all three facets of alexithymia. Parameter estimates and intraclass correlations suggested, though could not confirm, that it was shared environmental factors that contributed to difficulty identifying and communicating emotions (ID and COM), but shared genetic factors that contributed to externally oriented thinking (EOT). Between-twin cross-trait twin analyses revealed strong correlations between ID and neuroticism, and between COM and extraversion, and suggested that it is shared familial influences which account for these associations. CONCLUSIONS: The results of this study indicate that: (a) the different facets of alexithymia are influenced by familial factors; (b) the previously noted associations between ID and COM and trait affectivity are not merely methodological artifacts; and (c) the associations between ID and COM and trait affectivity are influenced by familial factors. The results also suggest that ID and COM are largely influenced by shared environmental factors, but that EOT is influenced by genetic factors.

A twin study of individual differences in perceptual asymmetry.

Individual differences in perceptual asymmetry have been associated with individual differences in cognitive abilities, personality characteristics, and psychiatric symptoms, for which between-person variation appears to be genetically influenced. Perceptual asymmetry scores are also associated with direction of handedness, for which between-person variation does not appear to be genetically influenced. To assess whether between-person variation of perceptual asymmetry scores is genetically influenced, we examined asymmetry on a freevision task of face processing, the Chimeric Faces Task (CFT), in a sample of 31 monozygotic (MZ) and 20 same-sex dizygotic (DZ) twin pairs. MZ and DZ within twin-pair resemblances were compared to assess genetic and familial influences on asymmetric hemispheric function. We found that twins within a pair were no more likely to resemble each other than were unrelated individuals. The results suggest that the between-person variation in CFT perceptual asymmetry is not influenced by genes or shared environment.