View Full Version : is not having ADHD genetic


daveddd
11-12-15, 10:42 PM
is this information useful ???or have some genetic researchers starting grasping at straws after 3 decades without being able to replicate a single study to prove ADHD is a genetic condition ?


http://www.ncbi.nlm.nih.gov/pubmed/26474816

The opposite end of the attention deficit hyperactivity disorder continuum: genetic and environmental aetiologies of extremely low ADHD traits.
Greven CU1,2,3, Merwood A3,4, van der Meer JM1,2, Haworth CM5, Rommelse N2,6, Buitelaar JK1,2.
Author information
Abstract
BACKGROUND:
Although attention deficit hyperactivity disorder (ADHD) is thought to reflect a continuously distributed quantitative trait, it is assessed through binary diagnosis or skewed measures biased towards its high, symptomatic extreme. A growing trend is to study the positive tail of normally distributed traits, a promising avenue, for example, to study high intelligence to increase power for gene-hunting for intelligence. However, the emergence of such a 'positive genetics' model has been tempered for ADHD due to poor phenotypic resolution at the low extreme. Overcoming this methodological limitation, we conduct the first study to assess the aetiologies of low extreme ADHD traits.
METHODS:
In a population-representative sample of 2,143 twins, the Strength and Weaknesses of ADHD Symptoms and Normal behaviour (SWAN) questionnaire was used to assess ADHD traits on a continuum from low to high. Aetiological influences on extreme ADHD traits were estimated using DeFries-Fulker extremes analysis. ADHD traits were related to behavioural, cognitive and home environmental outcomes using regression.
RESULTS:
Low extreme ADHD traits were significantly influenced by shared environmental factors (23-35%) but were not significantly heritable. In contrast, high-extreme ADHD traits showed significant heritability (39-51%) but no shared environmental influences. Compared to individuals with high extreme or with average levels of ADHD traits, individuals with low extreme ADHD traits showed fewer internalizing and externalizing behaviour problems, better cognitive performance and more positive behaviours and positive home environmental outcomes.
CONCLUSIONS:
Shared environmental influences on low extreme ADHD traits may reflect passive gene-environment correlation, which arises because parents provide environments as well as passing on genes. Studying the low extreme opens new avenues to study mechanisms underlying previously neglected positive behaviours. This is different from the current deficit-based model of intervention, but congruent with a population-level approach to improving youth wellbeing.
2015 The Authors. Journal of Child Psychology and Psychiatry published by John Wiley & Sons Ltd on behalf of Association for Child and Adolescent Mental Health.
KEYWORDS:
Attention deficit hyperactivity disorder; extremes; positive genetics; quantitative trait; twin

Amtram
11-16-15, 03:27 PM
The primary author is trying to separate out the various characteristics of ADHD into genetic and non-genetic types in order to establish one or more stable phenotypes for ADHD. She's got her hands in a lot of different pots, though, and it seems like she's testing a lot of research that's already been done in slightly different ways. She may come up with something worth exploring more deeply, but I didn't see anything novel enough to ask for full-text versions of the research.