A Monozygotic Twin Differences Study of Nonshared Environmental Influence on Adolescent Depressive Symptoms

Abstract

In French, the transcription of the same sound can be guided by both probabilistic graphotactic constraints (e.g., /epsilon t/ is more often transcribed ette after -v than after -f) and morphological constraints (e.g., /epsilon t/ is always transcribed ette when used as a diminutive suffix). Three experiments showed that pseudo-word spellings of 8-to 11-year-old children and adults were influenced by both types of constraints. The influence of graphotactic regularities persisted when reliance on morphological rules was possible, without any falling off as a function of age. This suggests that rules are not abstracted, even after massive amounts of exposure to a rule-based material. These results can be accounted for by a statistical model of implicit learning.

Dependent negative life events and sleep quality: An examination of gene–environment interplay

“…by causing stress to his/ her parents). Although a caveat of the present study, this method of assessment of dependent/ independent life events is standard and well accepted in the life event and depression literature (24,29,33,64,65), and has been used in previous papers from the G1219 study (28,43). An additional consideration is that the distinction between dependent and independent negative life events based on the "controllability" of the items may be confounded by the severity of the items included in the scales.…”

“…Dependent and independent negative life events were classified according to whether it is likely that their occurrence is the consequence of an individual's behaviour (24). This distinction between life events has been used in previous studies as well as other papers from the G1219 study (28,33). Both scales were standardized prior to analysis so that we could interpret changes in variance components across levels of negative life events as deviations from the mean rather than absolute values.…”

“…Although it is clear that both controllable and uncontrollable events have 4 negative consequences on sleep it is possible that these distinct types of negative life event are associated with sleep differentially. Other phenotypes, such as depression, have been found to be associated differentially with dependent and independent negative life events (28,29). Understanding more about the associations between these distinct types of negative life events and sleep quality is important because it may provide an insight into the possible mechanisms acting between sleep and the environment.…”

Nonshared Environmental Influences on Sleep Quality: A Study of Monozygotic Twin Differences

“…Dependent and independent negative life events were classified according to whether it is likely that their occurrence is the consequence of an individual's behaviour (Brown and Harris 1978). This distinction between life events has been used in previous studies (Silberg et al 2001) as well as other papers from the G1219 study Liang and Eley 2005).…”

“…The MZ twin differences design has been used to determine specific nonshared environmental effects for a number of traits, for example behavioural development and adolescent depression (Asbury et al 2003;Caspi et al 2004;Liang and Eley 2005), and is a simple yet powerful method of determining twin discrepancy that is independent of genetics and the shared environment (Pike et al 1996).…”