راهکارهای درمانی خاص در درمان لکنت زبان کلینیک تخصصی لکنت کرج ضلع شمال شرقی میدان والفجر-روبروی دارایی

راهکارهای درمانی خاص در درمان لکنت زبان کلینیک تخصصی لکنت کرج ضلع شمال شرقی میدان والفجر-روبروی دارایی

 

single gene and polygenetic components exist for persistent and recovered stuttering.

Genetic predisposition and environmental factors

One weakness in using family studies to support a genetic hypothesis to the onset of stuttering is that it is difficult to exclude alternative explanations of the data, and particularly nongenetic cultural transmission. Whether stutter¬ing is eventually discovered to reflect a single or multigene disorder, environ¬ment too will play a significant part. Some studies have looked not only at a genetic predisposition in stuttering, but also at the relationship between pos¬sible genetic components and developmental influences. Eaves, Kendler and Schultz (1986) argued for the possibility of two completely separate bipolar groups. At one end there is a group whose target behaviour can be considered genetically determined with little or no evidence of environmental influence; at the other, a nongenetic (or sporadic) group whose behaviour appears strongly related to environmental stressors, in the absence of genetic factors. Within these polar opposites, the expression (or lack of expression) of the disorder might be determined by the interaction of genetic and stress com¬ponents. Where there are low environmental stress factors, then a higher genetic loading would be needed to activate the disorder. In turn, a weaker susceptibility to a predisposition would require an increase in environmental effects to activate the problem (Monroe & Simmons, 1991).

There is tentative evidence for this type of interaction within the area of stuttering too. Poulos and Webster (1991) divided a group of 169 adolescents and adults who stutter into two: those with a positive family history for stuttering and those without. No between-group differences were found with regard to age of onset, type of stuttering behaviours and emotional factors, but a significantly higher number of the group with negative family history reported physical neurological trauma at birth, or in early childhood (37 percent as opposed to 2 percent). So here the bipolar states are: (a) stutter¬ing with a predisposition and no trauma; (b) stuttering without predis¬position but with neurological trauma. However, caution is needed when considering these data, because over 20

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