Most of the genetic covariation between major depressive and alcohol use disorders is explained by trait measures of negative emotionality and behavioral control.

BACKGROUND: Mental health disorders commonly co-occur, even between conceptually distinct syndromes, such as internalizing and externalizing disorders. The current study investigated whether phenotypic, genetic, and environmental variance in negative emotionality and behavioral control account for the covariation between major depressive disorder (MDD) and alcohol use disorder (AUD). METHOD: A total of 3623 members of a national twin registry were administered structured diagnostic telephone interviews that included assessments of lifetime histories of MDD and AUD, and were mailed self-report personality questionnaires that assessed stress reactivity (SR) and behavioral control (CON). A series of biometric models were fitted to partition the proportion of covariance between MDD and AUD into SR and CON. RESULTS: A statistically significant proportion of the correlation between MDD and AUD was due to variance specific to SR (men = 0.31, women = 0.27) and CON (men = 0.20, women = 0.19). Further, genetic factors explained a large proportion of this correlation (0.63), with unique environmental factors explaining the rest. SR explained a significant proportion of the genetic (0.33) and environmental (0.23) overlap between MDD and AUD. In contrast, variance specific to CON accounted for genetic overlap (0.32), but not environmental overlap (0.004). In total, SR and CON accounted for approximately 70% of the genetic and 20% of the environmental covariation between MDD and AUD. CONCLUSIONS: This is the first study to demonstrate that negative emotionality and behavioral control confer risk for the co-occurrence of MDD and AUD via genetic factors. These findings are consistent with the aims of NIMH's RDoC proposal to elucidate how transdiagnostic risk factors drive psychopathology.

Disentangling the relationships between maternal smoking during pregnancy and co-occurring risk factors.

BACKGROUND: Maternal smoking during pregnancy (SDP) has been studied extensively as a risk factor for adverse offspring outcomes and is known to co-occur with other familial risk factors. Accounting for general familial risk factors has attenuated associations between SDP and adverse offspring outcomes, and identifying these confounds will be crucial to elucidating the relationship between SDP and its psychological correlates. METHOD: The current study aimed to disentangle the relationship between maternal SDP and co-occurring risk factors (maternal criminal activity, drug problems, teen pregnancy, educational attainment, and cohabitation at childbirth) using a population-based sample of full- (n=206 313) and half-sister pairs (n=19 363) from Sweden. Logistic regression models estimated the strength of association between SDP and co-occurring risk factors. Bivariate behavioral genetic models estimated the degree to which associations between SDP and co-occurring risk factors are attributable to genetic and environmental factors. RESULTS: Maternal SDP was associated with an increase in all co-occurring risk factors. Of the variance associated with SDP, 45% was attributed to genetic factors and 53% was attributed to unshared environmental factors. In bivariate models, genetic factors accounted for 21% (non-drug-, non-violence-related crimes) to 35% (drug-related crimes) of the covariance between SDP and co-occurring risk factors. Unshared environmental factors accounted for the remaining covariance. CONCLUSIONS: The genetic factors that influence a woman's criminal behavior, substance abuse and her offspring's rearing environment all influence SDP. Therefore, the intergenerational transmission of genes conferring risk for antisocial behavior and substance misuse may influence the associations between maternal SDP and adverse offspring outcomes.

Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis.

The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with lambda max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530-540 nm. The cornea and oil droplets were found to be transparent across a range from 350-700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.