LONGITUDINAL PREVALENCE OF STEREOTYPIES IN AUTISTIC VS.NON-AUTISTIC DEVELOPMENTALLY DISABLED CHILDREN

Objectives: This longitudinal study examines the effect of autism and developmental disabilities on the prevalence and characteristics of stereotypies, defined as repetitive, rhythmic and purposeless movements, in a group of children evaluated during pre-school and again at 9 years of age.

Methods: Stereotypies were coded from 15 minutes of videotaped standardized play sessions in 208 preschoolers (mean age 4½ years): 95 autistic children (61 LowIQ [<80], 34 HighIQ [=80]) and 113 controls (44 LowIQ nonautistic, 69 HighIQ developmentally language disordered) and 99 nine year olds (75 of them seen at both ages), 58 autistic (38 LowIQ, 20 HighIQ) and 41 non-autistic controls (14 LowIQ, 27 HighIQ).

Results: Of the 208 preschoolers, 104 had stereotypies, of which 75% were autistic (p<. 0001). Cognitive level did not affect the prevalence of stereotypies in either autistic or non-autistic pre-school children (p=0.16), but was significantly associated with the number of stereotypies per child (p=0.0016). At age 9, 34/99 had stereotypies, of whom 88% were autistic (p=<0.0013). At the older age, low cognitive level increased the prevalence of stereotypies (p=0. 0003). Across all groups most stereotypies were complex, non-dystonic movements involving multiple body parts. Autistic children had higher numbers of hand movements.

Conclusions: More autistic than non-autistic children at preschool and age 9 exhibit stereotypies. Over time, fewer children with IQ=80, whether autistic or not, have stereotypies. Few characteristics of stereotypies seem to be specific to autism. Temporarily suppressible like tics, stereotypies may index prefronto-striatal dysfunction. Further research will investigate their trajectories with maturation and their correlation with brain imaging and neurotransmitter activity. Study supported by NINDS program project #20489 and by a grant from NAAR.