Down Syndrome Abstract
of the Month:
May 1998
Behaviour phenotype for Down's syndrome.
Collacott RA; Cooper SA; Branford D; McGrother C
Br J Psychiatry 1998 Jan;172:85-9
Western Isles Hospital, Isle of Lewis, Scotland.
Abstract:
BACKGROUND: For more than a century, the idea of particular personality/behavioural characteristics being associated with people with Down's syndrome has been explored, but with inconclusive results.METHOD: The Disability Assessment Schedule was used to ascertain the behavioural profiles of 360 adults with Down's syndrome and 1829 adults with learning disabilities of other etiologies, who were the whole identified population within a defined geographical area. Comparison was made between the two total groups and additionally for the subgroups aged < 35 years and aged > or = 35 years. Comparison was also made with regards to cluster analysis findings.
RESULTS: Despite an equal age and developmental quotient, the Down's syndrome group were less likely to demonstrate maladaptive behaviours. The behaviour characteristics of the adults with Down's syndrome remained constant in the younger and older age groups. Cluster analysis demonstrated adults with Down's syndrome to have an increased prevalence in cluster groupings with lower rates of maladaptive behaviours.
CONCLUSIONS: This study confirms there to be a behaviour phenotype among adults with Down's syndrome. The reasons for this (e.g. genetic/psychological/social) require further research. Such research may establish a better understanding of the etiologies of maladaptive behaviours among people with learning disabilities in general.
My comments:
In genetics, a "phenotype" refers to a category or group that can be assigned to an individual on the basis of features or characteristics that reflect that individual's genetic make-up. For instance, a phenotype may describe something as simple as eye color or as complex as a behavior pattern. The purpose of the above paper was to answer the often asked question: "Does the presence of the third 21st chromosome give people with Down syndrome a specific behavior or personality pattern?" (How many times have you parents heard the "sweet and loving disposition" remark?)In comparing the adults with Down syndrome (DS), the authors looked at 13 maladaptive behaviors, as described by the standardized Disability Assessment Schedule questionnaire. These behaviors were: aggression, antisocial behavior, property destruction, disturbing others at night, scattering objects, attention-seeking, sexual delinquency, self-injury, uncooperativeness, untruthfulness, excessive activity, excessive noise and hiding ("absconsion"). Of these, the adults with DS had a significantly lower rate of all behaviors except sexual delinquency and uncooperativeness. (Note that the adults without DS were chosen from a registry of those with learning disorders, and psychiatric diagnoses weren't available to the authors. This is a limitation on the study.)
The authors then broke this comparison down into two groups: adults 35 years old and older, and those younger than 35. Under 35 years, the adults with DS had significantly less maladaptive behavior for all categories except antisocial behavior, sexual delinquency, and untruthfulness. For those 35 and older, the adults with DS had significantly less maladaptive behavior for all categories except disturbing others at night, scattering objects, sexual delinquency, uncooperativeness, untruthfulness and hiding.
From these results, the authors conclude that there is a behavioral phenotype in which adults with DS are less disruptive. The authors acknowledge that most of the behavioral studies in the past were on children, but state that they used adults because the personalities are "shaped and developed" by that time.
Personally, I'm going to have to see a few more studies before I'm convinced. I'm reminded of the mother of a girl with DS who would respond to the comment about children with DS being so sweet and loving with: "I'll call you the next time she puts the cat in the dryer".