Saturday, December 18, 2010

The Evidence on Weighted Vests

The Evidence on Weighted Vests
Many kids with identified (and non-identified) special needs such as autism spectrum disorders, sensory processing disorders, ADD/ADHD, developmental delays demonstrate difficulties with initial and sustained attention to task, focus, self-stimulating behaviors, self-abusive behaviors and tactile and sensory defensiveness.  Some kids will also appear not to be ‘grounded’.  That’s not an official diagnosis and it’s hard to describe conclusively, but ‘ungrounded’ kids will frequently crash into objects/walls/people, appear restless and will roam aimlessly, and just don’t seem firmly in place or on the ground (I know that sounds a bit weird but trust me, there are kids who look like this and therapists often know them when they see them).  Although the reasons for these difficulties are varied and many, one intervention that many kids respond very well to is the wearing of weighted vests over a period of time. 

In 2005, my graduate students and I took on the task of looking at the evidence of two very common pediatric interventions: Weighted Vests and the Brushing Protocols.  In this post, I’ll focus on the weighted vests and will address the brushing protocols in another posting soon.  Despite the popularity of using weighted vests, only two actual studies have been completed and published in occupational therapy literature to date.  Interestingly, there are a couple of myths about the weighted vests as well that I’ll address here.  Before we dive into the evidence (don’t worry, it won’t be a boring read!), let me start with some definitions along with ‘the why’ for using weighted vests.

Definitions:
Tactile sensitivity (also known as tactile defensiveness) occurs when the light touch receptors, which are located near the skin surface, are hyperactive or hypersensitive.  These light touch receptors are particularly prevalent in the hands and feet (because there are so many more touch receptors in the hands and feet than the rest of the body with the exception of the lips/mouth – sensitivity of the light touch receptors of the mouth/lips is known as oral defensiveness).  Our light touch receptors alert us to subtle changes in the environment near us and help us know whether some of these changes are dangerous.  For instance, when getting near a stove that is turned on, our light touch receptors alerts us that it is hot and possibly dangerous and our light touch receptors will alert us to when someone enters our personal space.  Hyperactive or hypersensitive light touch receptors will tend to treat all incoming sensations as dangerous and the body will react accordingly (i.e.: the child will move away, become irritable, will sometimes even hit out). 

One of the ways to address tactile defensiveness (and sensory defensiveness in general) is to stimulate deep touch receptors (these are located just under the skin surface).  The cool thing about deep touch receptors is that they will 'turn off' the sensitivity of the light touch receptors and with sustained deep touch, there is an increase in the dopamine neurotransmitters (this is why a great massage - which is deep touch - feels so relaxing and good overall).  Many therapists will use ‘sensory tubs’ and will have a child with tactile defensiveness dig in heavy-ish materials like rice, beans, popcorn kernels (think how heavy a bag of each of those is compared to the same sized bag of pasta or other similar food products) to stimulate the deep touch receptors to help decrease the hyperactive light touch receptors.  Other activities that help are things like clapping our hands or rubbing them vigorously or waving them forcefully or pounding the hands on knees or tabletop (I often started many fine motor activity with these precursors). 

Proprioception is actually another sense (in addition to touch, taste, auditory, vision, smell) and it tells us where our body and body parts (e.g.: arms, hands, legs, etc.) is and what they are doing.  These receptors are located in the muscles of the body and are very prevalent in the tendons (tendons are the ends of the muscle strands that surround and go across joints – you can easily feel these tendons in any joint of your body). The receptors let you know, without you having to look, what your body is doing.  For instance, you do not need to look down to see which direction your feet are pointing and you will know that you have three fingers extended when they are behind your back.   Proprioception is one of the most powerful senses when stimulated and is extremely effective in decreasing sensory defensiveness.  Proprioceptors stimulate the serotonin neurotransmitters (Hanschu, 1998; Reeves, 1998).  If you’ve ever been to an good chiropractor for an adjustment or had joint compression/traction performed by a massage therapist, you know how deeply relaxing and ‘grounding’ these treatments can be and you may feel an increase in attention or focus after such treatments.  In my workshops, I often ask participants to stimulate the proprioceptors of one hand by gently but firmly press relaxed fingers towards the palm of the hands, ten times to each finger.  Participants will report an increase in blood circulation, a sense of ‘heaviness’ but at the same time a sense of ‘lightness’ and lastly a significant increase in awareness of that hand compared to the other hand.  These are ‘grounding’ sensations.  The best way to stimulate proprioceptors is to apply pressure to them either through joint compression or traction or from sustained pressure from ‘heavy work’ like carrying books, pulling a cart or by wearing weighted objects like vests, lap pads, blankets, etc.

OK, now that we have covered some basic definitions and ‘the why’, let’s look at the evidence that supports the use of weighted vests.

The Evidence:
As I noted earlier, there have only been two published studies on the effectiveness of using weighted vests in improving children’s behaviors and functioning at school.  First, I’ll do a summary of each study’s findings and then I’ll get into the recommendations based on this evidence.

Article:  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.
Study Objective: Examined effectiveness of using a weighted vest for increasing attention to fine motor tasks and decreasing self-stimulatory behaviors in preschool children with pervasive developmental disorders (PDD).
Who:
  • Five preschool children with Pervasive Developmental Delays (PDD); 3 boys & 2 girls
  • Aged 2 yrs 7 mon to 3 yrs 1 months
  • Weighed 25.5 lbs to 37 lbs
  • ·All were enrolled in 5-day-a-week preschool class in New York city for 3 hours daily; program used an Applied Behavior Analysis approach
The Intervention:
  • All vests were the same brand
  • All vests were weighted with 1 lb of weight evenly distributed in the front/back pockets of the vest
The Study Approach:
  • Quasi-Experimental, Single Subject ABA Design; in this design, the children are observed without wearing the vests, then observed wearing the vests, and then observed a final time without wearing the vests.  In this design, the individual child’s performance during each stage is compared but the children are not compared to each other.  In other words, the child serves as both his/her own control ‘group’ and as his/her own experimental ‘group’; this is a strong research design because most of the typical variables in any experimental study are eliminated since the child is the same person in each stage and in each ‘group’.
  • Each stage (baseline – before wearing the vest, intervention – wearing the vest, withdrawal – no longer wearing the vest) lasted 2 weeks. 
  • During the intervention stage, the vests were worn for 2 hours straight, then taken off and not worn again during the rest of the day in the class
  • Observation sessions during each stage took place during a familiar, structured fine motor activity & at the same time of day 
  • There were no reported changes in home or school routines
The Results:
Intervention phase (2nd two-week period):
  • Decrease in number of distractions for all five children
  • Increased focused attention for all five children
  • Decrease in self-stimulatory behaviors for four children.
  • One child, who did not demonstrate a decrease in self-stimulatory behavior, did demonstrate less self-abusive behaviors
  • Greatest improvement in all three measures were noted for smallest child who weighed 25.5 lbs
Withdrawal phase (3rd two-week period):
  • Decrease in duration of attention
  • Increase in distractibility (but not to the baseline levels)
  • Self-stimulatory behaviors increased (but not to the baseline levels)
Possible Implications to Practice:
  • Weighted vests appear to have a very positive effect for pre-school children with PDD who have difficulties attending to tasks and exhibit self-stimulatory behaviors
  • Proportion of the child’s weight and to the weight amount in the vest may be a factor; all the children wore the same weight (1 lb) in their vests but the smallest child demonstrated the most improvement suggesting that weight proportions should be considered.
  • Withdrawal phase indicated regression but not to the extent demonstrated in the baseline phase, possibly suggesting that weighted vests may have long-term effect even when it’s not worn for a period of time.
  • Although  this study was specific to pre-schoolers in New York city with PDD, it is possible that these positive results may occur for other children, who have difficulties attending to task and demonstrate self-stimulating behaviors, in other locations and settings.
Article:  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.
Study Objective: Investigated the effects of wearing a weighted vest on on-task behaviors in the classroom in children identified with ADHD
Who:
  • Children receiving school-based occupational therapy in a Midwestern rural school
  • All have ADHD diagnosed by physician or scored as high/problem range on hyperactivity and attention area of the Conners’ Teacher Rating Scales
  • Aged 5 yrs 9 mon to 6 yrs 10 months
  • 2 girls eligible for special education as speech and language impaired
  • 2 boys eligible for special education as physically or otherwise health impaired
  • All demonstrate sensory modulation difficulties
The Intervention:
  • Weight of vests were calibrated to close to 5% of the child’s weight as possible
  • Children were given the vests to wear at times when they weren’t being observed so they did not associate the vests with observation periods
The Study Approach:
  • Quasi-Experimental, Single Subject AB Design; in this design, the children are observed without wearing the vests and then observed wearing the vests.  In this design, the individual child’s performance during each stage is compared but the children are not compared to each other.  In other words, the child serves as both his/her own control ‘group’ and as his/her own experimental ‘group’; this is a good research design because most of the typical variables in any experimental study are eliminated since the child is the same person in each stage and in each ‘group’.
  • Each stage (baseline – before wearing the vest, intervention – wearing the vest,) lasted 15 days (unclear whether these were 5-day weeks or actual 15 days). 
  • Each child was observed for 6 baseline and 6 intervention observations each for 15 minutes at a time
  • Vest was put on the child 5 minutes prior to the beginning of the timing and were taken off after the completion of the 20 or 30 min activity
  • There were no reported changes in home or school routines
The Results:
  • All 4 children showed significant increases in on-task behavior while wearing a weighted vest.
  • Student 1 demonstrated a 25% increase in the amount of time on task while wearing the vest.
  • ·Students 2, 3, & 4 demonstrated a 17% to 18% increase in the amount of time on task while wearing the vest.
  • Teachers report more cooperation and decreased signs of hyperactivity during the intervention stage
  • Students 1, 3 & 4 asked to wear the vest at times other than the timed observation periods
Possible Implications to Practice:
  • Weighted vests appear to have a positive effect on the amount of on-task behavior for 5-6 year old children with attention deficit hyperactive disorder (ADHD)
  • Children requested to wear the vests outside the timed observations and reported that the vests “feel good” “feel comfortable” indicating insight regarding the benefits of the vests.  
  • Although this study was specific to 5-6 year olds with ADHD in the Midwest, it is possible that these positive results may occur for other children, who have difficulties attending to task, in other locations and settings.
The Myths About Wearing Weighted Vests:
In my years of practice and teaching and in my communications via listservs, conferences and in my workshops with other therapists across the country, I’ve heard two primary instructions regarding weighted vests:
  • Weighted vests should only be worn for a maximum of 15 or 20 minutes (depending on which version one hears) because there’s an ‘acclimation’ effect.
  • Weighted vests should never exceed 5% of a child’s body weight.
Despite a thorough search by my graduate students and me, we could not find any evidence in occupational therapy or neurology literature to support either claim.  It is my opinion that these notions are actually ‘OT urban myths’. ;) 

Weighted Vest Recommendations:
In my experience in using weighted vests with over 300 kids over the course of my career and based on the evidence presented here, my recommendations are the following:
  • Use weighted vests calibrated to 5% of a child’s body weight at least initially.  In my experience, some children benefitted from more weight – most in the 6 to 7% range with a few benefitting most from 10%.  In these circumstances, I increased the weight 1% at a time and until the final weight determination, I closely observed the child for a period of days (usually 3-5 days), relied on teacher report and most importantly, asked the child for their impressions of the increased weight until we reached desired benefit.  Again, most increases were only to the 6 to 7% range.
  • I often had difficulties with adherence to a wearing schedule of X minutes (ie: 20 minutes, 30 minutes, etc.).  Teachers are so busy and must meet the needs of all the children in their classrooms that it is hard for them to remember when the vest was put on or sometimes to even remember to put on the vest.  But I’ve had excellent success by pairing the vest with the activity.  For instance, many times a weighted vest is used during table/desk activities as that is when the child generally needs increased attention to tasks (which the evidence supports is improved by wearing weighted vests).  Thus, I would often recommend that the child wear the vest when he or she is sitting at his/her seat/desk and the vest should remain on the chair when the child is away (for recess or PE).  Even if the time-at-desk might be for 40 minutes (or longer), I’ve seen no detrimental effect in any child for wearing the vest for a longer period of time.  In fact, some children have benefitted from wearing the vest all day; again, the length of vest-wearing time is closely monitored by me and the teacher and very importantly, the child is asked for his input about the wearing schedule.
  • My final recommendation is to be aware of the social implications of having a child wear a vest in his classroom (particularly for children included in general education classrooms).  Thus, when I would make a recommendation for a child to wear a weighted vest, I would also provide 2-3 other non-weighted vests (these I would pick up at garage sales or the local Goodwill store) and the teacher would assign the non-weighted vests to certain class roles such as one for the Birthday Girl/Boy or the Lunch Counter or the Door Holder or she would simply randomly assign the vests to other children.  This approach has been very successful in vest-wearing compliance by the child and ensuring that the child does not feel or look ‘different’.
I hope this information has been helpful – feel free to share your own experiences or thoughts about weighted vests by commenting to this post.

*This information was originally published in the following two articles: 
  • Honaker, D. & Rossi, L. (2005, December).  Proprioception and participation at school: Are weighted vests effective? Appraising the evidence Part Two.  Sensory Integration Special Interest Section Quarterly.  Bethesda, MD: AOTA 
  • Honaker, D. & Rossi, L. (2005, September).  Proprioception and participation at school: Are weighted vests effective? Appraising the evidence Part One.  Sensory Integration Special Interest Section Quarterly.  Bethesda, MD: AOTA.
(c) 2010 by DeLana Honaker, PhD, OTR

9 comments:

  1. This was a great read! Do you have any idea of the history of the weighted vest? Im writing a paper for class, and cant seem to find anything.

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  2. I also have seen excellent results in children wearing vests as needed, and not strictly adhering to the "15-20 minute rule". Great post!

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  3. Thank you for this post. My child has ADHD and we chose not to medicate, but to use herbs. The herbs are fabulous, but there are times at school during a test or in centers that some extra 'calming and focusing' techniques are needed.

    I will be looking into this for my child.

    Thank you.

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  4. Hi DeLana,
    My son is 5 yrs with ADHD diagnosis.His weight is 20 kgs.

    For classroom usage, his OT guys have recommended to use 2kg vest and increase weight upto 5 kg, depending on benefits observed and activity in which he is involved. vest is having provision to increase weight.

    From your article above, it seem that weight recommendation of our OT guys is on higher size.

    Would appreciate your advise/comment.

    Thanks,
    Deepak

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    Replies
    1. HI Deepak -

      Some kids benefit from greater weight and it sounds like your son's OT is starting with 10% and possibly may move to 25% of your son's weight; I think 25% might be on the very high end but I do not know your son but I believe your OT is approaching this process correctly by starting with the 10% weight and then observing to see how well that level of weight helps in achieving the desired outcomes. As long as you and the OT work together, I have no doubt that you both find the right weight that best benefits

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  5. The comment above about kids not wanting to look or feel different while wearing a weighted vest in school...where I work, we make a shoulder pillow that looks like a cute kitty cat that is not only weighted, but can be warmed in the microwave to help with those sensory difficulties. There is also a flat, rectangular one that resembles a turtle designed to be used across the lap while at school or at night to help sleep. With these helpful items, they would be the envy of the other kids. www.michaeltorie.com under "Pre-Loved" category. Hope this is a help to someone.

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  6. Where can I read your texts about wight vests?

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  7. Thank you for the information on the weighted vest. The preschool that my grand son goes to in New Jersey is recommending that he get one. They are pricey and I don't think insurance pays for them so I was wondering if there were any studies that showed their use actually helped children with ADHD to stay on task..

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  8. Thank you for the information on weighted vests. The preschool in New Jersey that my grandson goes to is recommending that he wear a weighted vest. I don't think that insurance will pay for them and they are pricey. If they work as described in the studies above,the money will be well spent.

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