Over a year ago I wrote an article about a case report indicating that, for one child, pressure vests were not found to be effective in promoting engagement behavior (see my criticism of using case reports for conditions that are not extremely rare). The same journal just published a slightly larger, and therefore more informative, study examining the effectiveness of weighted vests for reducing stereotyped behaviors  (e.g., hand flapping, sniffing, rocking, spinning objects, echolalia, etc) in children with severe autism. These behaviors can have a negative impact on the child’s social relations and academic functioning, and therefore are often the target of interventions. In the study, Dr. Sandra Hodgettes and her colleagues at the University of Alberta, explained the “homeostatic” theory about stereotyped behaviors in autism. This theory purports that individuals with autism engage in stereotyped behaviors in order to compensate for a state of over or under physiological arousal. That is, stereotyped behaviors are believed to help individuals bring their arousal level back to “normal”. So, how are weighted vests supposed to help?

Pressure or weighted vests are supposed to provide enough sensory stimulation to produce the right amount of physiological arousal so that the person does not need to engage in stereotyped behaviors. If this is true, then the use of weighted vests should have an impact on physiological markers of arousal. For example, if weighted vests reduce physiological arousal, then we should see a change in heart rate. We don’t really know if this is true because the authors indicated that no study had examined the effects of weighted vests on heart rate. Thus, the researchers of this study were interested in examining whether the use of weighted vests would decrease stereotyped behaviors, and whether the vests would impact the heart rate of the participants.

The study involved 6 mostly non-verbal children with severe autism between the ages of 4 and 10 (5 boys and 1 girl). The kids participated in a withdrawal design for 4 weeks, during which they alternated each week between one condition (weighted vest) and the other (no vest). For example, one child would use the weighted vest during week 1, then no vest during week 2, then vest during week 3, and finally no vest during week 4. If the vest is effective, you would see an reduction of stereotyped behaviors during the weeks the child used the vest, and an increase of such behaviors during the weeks he/she didn’t use the vest. Likewise, if the vest had an impact on heart rate, the heart rate would change based on whether or not the child was wearing the vest.

The results:

Below you can see the % of intervals during which the child engaged in stereotyped behaviors in one of the participants during the different weeks of the study.

As you can see, during all weeks stereotyped behaviors were observed between 70 and 100% of the time intervals examined, and there was no change across the different weeks. This indicates that the vest had no impact on the presence of stereotyped behaviors. Also, there was no difference between the week the vest weighed 5% of the child’s body weight and when the vest weighed 10% of the body weight. Unfortunately, this was the general patterns among the participants. Overall, the use of the weighted vest did not result in a reduction of stereotyped behaviors or in a change in heart rate. This is consistent with most of the previous studies that have used the proper research designs and which have also failed to find evidence for the effectiveness of these vests.

There was one exception, however. In one child, the weighted vest resulted in an 18% decrease in stereotyped behaviors, which led to a PND of “questionable effect”. PND is a statistic that examines the likelihood that the effect observed is due to the treatment as opposed to chance or other factors. So sadly, even for the single child for which the vests appeared to be effective, it was unlikely that the effect observed was due to the treatment.

The authors concluded:

This study’s results do not support the use of weighted vests to decrease motoric stereotyped behaviors, nor does it support the theoretical basis for this modality.

Although we need studies with significantly more participants so we can firmly establish whether these vests are effective, the best studies to date have failed to show that this intervention is effective in reducing stereotyped behaviors in most children.

The reference:
Hodgetts, S., Magill-Evans, J., & Misiaszek, J. (2010). Weighted Vests, Stereotyped Behaviors and Arousal in Children with Autism Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-010-1104-x
ResearchBlogging.org

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7 Responses to Weighted vests for children with severe autism: More evidence against them?

  1. Calli Arcale says:

    I know when a vest was tried for my daughter, it wasn’t very useful. However, I’m not convinced this study has really invalidated the vests. It has, rather, invalidated the idea that they reduce stereotyped behaviors. But it may be that we need other markers to properly evaluate the vests or other weighted products. I think we can safely say now that it’s not about increasing the child’s physiological arousal. It could, however, be that pressure is in some way helpful. I’m a little doubtful based on the fact that many people say the vests only work for a while — this would be consistent with a placebo effect, and even if real, would give them little value as a long-term intervention. On the other hand, Temple Grandin got so much peace and comfort out of her squeeze box; it might just give the kid something else to think about for a little while, in which case there’s a huge range of things which might work, and would likely be different for different patients, since they’d probably be working on a more symbolic level — a touchstone in a chaotic life rather than something directly helpful.

    They are definitely oversold; I’m pretty sure of that, and this research does help support my opinion.

    • Thanks Calli for the comment. You are correct that this study only speaks to the effectiveness of these vests for reducing stereotyped behaviors and affecting heart rate. It is indeed possible that there may be other outcomes that the vest are effective for, but which were not examined in the study.

  2. We use weighted snakes, (ten of them, sewn for us by a parent) in our Stage Play Acting Classes for children with autism. Our young acting students, age five to nine years, are told that if they have a hard time sitting in the audience they can ask for a snake or go out with an Acting Buddy (volunteer) and jump ten times on a trampoline then come back. Most kids choose the snakes more often than they choose the trampoline even though the kids love jumping on the mini-tramp before class starts. They enjoy the class, we think, and don’t want to miss anything. There is no way for us to know why the snakes seem to help the kids sit but we and the kids are convinced that they do help. We never did a study to prove it though. We do know it goes better if we offer a snake rather than tell the child to “sit still and wait for a turn.” We don’t know if the children are engaged mentally in what is going on because of the snakes. We are happy if children don’t distract other children as much when holding a snake. It does seem like holding a snake keeps kids from doing things like standing up and flicking the theater type chairs up and down or running back behind the theater curtains. The volunteers like having something to offer a child who seems agitated or bored. It may be that weighted items have been over-sold as a learning support but once a strategy is in the tool box of a teacher, there are any number of creative ways the teacher may then use the strategy.

    I continue to hear from many parents that their child will only fall asleep or stay asleep all night if sleeping under a weighted blanket. The explanation that I have heard for this is that in the dark the child has more body awareness than he or she would without the blanket. Is that the same explanation as the one being tested in this study?

  3. Sadly the conclusions reached in this blog posting appear over-reaching although I am in agreement with the statement that larger studies are needed before determining whether the weighted vest is helpful or not. Also, remember that the only conclusions one can reach in any single subject design study is the effectiveness of an intervention for that particular study participant; these results cannot be generalized beyond the that particular study participant (Gliner & Morgan, 2000). As I read the original article, it was clear that the vests were not used appropriately or with the understanding of the purpose of the vests. May I refer you to two studies (both single subject designs – one was ABA and the other was AB). Both studies clearly defined the measures used (observations) and both showed significant improvement in attention and behaviors. I have reviewed both articles in my blog at http://www.delanah.com/2010/12/evidence-on-weighted-vests.html#more. My own anecdotal experience in using weighted vests for 300+ kids in my 16 year career is consistent with these two studies as well as one that I conducted but have not published as yet. I hope this comment is helpful in further understanding the use of weighted vests. :)
    DeLana Honaker, PhD, OTR
    Reference:
    Gliner, J. & Morgan, G. (2000). Research methods in applied settings. Mahwah, NJ: Lawrence Erlbaum Associates, Inc.

    The Two Studies Using Weighted Vests:
    Fertel-Daly, D., Bedell, G., & Hinojosa, J. (2001). Effects of a weighted vest on attention to task and self-stimulatory behaviors in preschoolers with pervasive developmental disorders. The American Journal of Occupational Therapy, 55(6), 629-640.

    VandenBerg, N.L. (2001). The use of a weighted vest to increase on-task behavior in children with attention difficulties. The American Journal of Occupational Therapy, 55(6), 621-628.

  4. CHRISTY says:

    CAN WE SAY CRUEL, CRUEL, CRUEL. I THINK ALL YOU PEOPLE ARE NUTS!

  5. vikki says:

    the weighted vest helps keep the child somewhat grounded. autistics feel “lost in space” its just a simple way to help keep them grounded. When they have a tantrum, and, or for the high functioning child, these vests can help. I have personally seen my autistic 3 year old go from running wild, and screaming, not transitioning, not focusing on the task as hand, and then we put the vest on, and within a minute he’s calmer, and then we can get him to focus, and transiiton with less problomatic behaviors. It makes me wonder how they were testing these kids….

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