Moderate alcohol consumption in pregnancy and subsequent left-handedness

Left-handedness is statistically linked to lifetime experimentation with illicit drugs

Handedness has been linked to an enhanced risk of alcohol abuse, while less is known about other drugs. A convenience sample of 1004 male and female Italian participants (females=58%) from the general community (18 to 65 years old: average age = 30; standard deviation = 10, median = 25) was asked about: handedness (preference in writing); lifetime use of alcohol, tobacco, and illicit drugs; levels of psychological distress, as measured by the General Health Questionnaire (GHQ); and levels of delusion proneness, as measured by the Peters et al. Delusions Inventory (PDI). Overall, 92 individuals (9.2%) were classified as left-handed, with no significant difference reported among genders. Lifetime use of illicit drugs, primarily cannabis, was reported by 20% of the sample. In a multiple logistic regression analysis, after taking into account sex, age, and caseness on GHQ and PDI, left-handed people in the sample were statistically more likely to report lifetime experimentation with heroin, ecstasy/amphetamine, and, marginally, hallucinogens, but not alcohol or tobacco. Different mechanisms might contribute to an explanation of greater lifetime experimentation with some illicit drugs among left-handed people as compared to right-handed people. However, replications with clinical samples are necessary before any definitive statements can be made.

Atypical functional lateralization in children with fetal alcohol syndrome

In order to explore effects of prenatal alcohol exposure on functional lateralization, item tasks measuring preferences of hand, foot, eye, and ear were administered to a sample of 23 children diagnosed with fetal alcohol syndrome (FAS) compared with typically developing (TD) children. In addition, a dichotic listening task was administered to a subsample of 11 children with FAS and a TD group of comparable age, sex and handedness. The children with FAS were characterized by increased nonright-handedness compared with TD children. No differences were evident for preferential use of foot, eye, or ear. Moreover, children with FAS displayed more right ear extinctions during dichotic listening relative to TD children, indicating a lack of right ear advantage. The results add to findings of decreased manual asymmetry and less left-lateralized speech perception in children with developmental disorders, and are further discussed in relation to the high incidence of callosal abnormalities in alcohol-exposed children.

Handedness and time to pregnancy

BACKGROUND

Nonright-handedness, particularly mixed-handedness, has been associated with a number of medical conditions. We examined whether handedness was associated with fecundity, measured by time to pregnancy.

METHODS

We used data on parental handedness and time to pregnancy from 2 regional birth cohorts in Denmark: the Aalborg-Odense Birth Cohort (1984-1987) and the Aarhus Birth Cohort (1990-1992) (n = 5808 and 3426, respectively). We applied discrete-time survival analysis to assess fecundity in relation to handedness.

RESULTS

In both cohorts, we saw a slightly lower fecundity in individuals who reported being mixed-handed.

CONCLUSIONS

Our data showed a modest association between mixed-handedness and subfecundity, which suggests that these traits may share a common etiology, perhaps tracing back to the prenatal period.

Handedness and mortality: a follow-up study of Danish twins born between 1900 and 1910

The declining prevalence of left-handed individuals with increasing age has led to two main avenues of hypotheses; the association is due either (1) to a birth cohort effect and/or an age effect caused by a switch to right-handedness with advancing age or (2) to mortality selection that reduces survival in left-handed individuals, or both. It is uncertain whether a cohort or age effect can explain the decline in age-related prevalence, and conflicting evidence exists in favor of the mortality hypothesis. We compared mortality in a subgroup of 118 opposite-handed twin pairs by counting in how many instances the right-handed twin died first. There was no evidence of differential survival between right-handed and non-right-handed individuals in the entire 1900-1910 cohort. With respect to the number of right-handed twins who died first, there was no material disadvantage among those who were not right-handed. In 60% (95% confidence interval = 49.0-71.5%) of dizygotic pairs, the right-handed twins died first. In 50% of monozygotic pairs, right-handed twins died first. The prevalence of not being right-handed was higher among males (9.2%) than females (6.5%); there was a similar frequency of non-right-handedness in monozygotic (8.0%) and dizygotic (7.8%) twins. We did not find evidence of excess mortality among non-right-handed adult twins in this follow-up study.

Is left-handedness a sensitive marker of prenatal exposures or indicators of fetal growth?

Left-handedness has been suggested as a sensitive marker of neurotoxic exposures or of the hormonal environment in fetal life. The prevalence of left-handedness was the subject of a follow-up study in children aged 5 to 9 years and correlated to exposures recorded by their mothers during pregnancy. Altogether 965 children were studied by means of questionnaires completed by the mothers. The response rate was 91%. Smoking, head circumference, Apgar score and indicators of fetal growth retardation were found not to be associated with increased prevalence of left-handedness.