The Hug Machine: How does Hug Therapy Work to Eliminate Stress?

Hug therapy can be applied in various ways such as a hug machine. What are the mechanisms of hug therapy that cause stress relief?

Happy Friday Truhugs Readers! As you’ve read through the plethora of information we’ve laid out for you, have you ever stopped and thought: Why do weighted blankets work well for some people and not others? If you answered yes to this question, then you’ll enjoy today’s article, which stems from a study that sought to determine the components of deep pressure stimulation (hug therapy) — in the form of a hug machine– that cause changes in people who experienced anxiety.

For our new readers, hug therapy is the sensation of physical contact that is somewhere in between the two extremes of a light tickle, and a painful, heavy grasp. Occupational therapists have implemented hug therapy as a way to alleviate symptoms of mental health ailments through various methods such as physical touch (hugs), or mat sandwiches (the act of having a person being squeezed in between two mats), a weighted blanket, or a hug machine. Hug therapy is a sought after technique by therapists because

  • It’s a noninvasive intervention
  • It’s easy to self-apply
  • There are no known harsh side effects
  • It generally feels good, so people are more motivated to utilize the intervention on their own

Research has shown us that hug therapy is useful in attenuating some symptoms of mental health ailments, and other times it is not helpful. So what’s the difference? Is it the temperature? The need for contact? The amount of pressure? A personality trait that makes someone predisposed to being more affected by hug therapy? The study we are dissecting today is a pilot study, so, unfortunately, it does not cover all of these components to answer every single one of our questions; however, it does address the following variables of hug therapy:

  • Confinement
  • Personality Traits
  • Self- control ( the ability for one to control their hug therapy pressure)

The researchers pointed out that it is unclear if hug therapy causes shifts in some people because of the confinement (or swaddling) or if the mentality of the individual having hug therapy forced upon them is forced submission, where they accept that they have no control and give in to the sensations.

In a previous article, we dissected literature on Temple Grandin’s hug machine; a central component of this apparatus was to instill the ability for people to control their own pressure. The majority of people who used her self-developed hug machine reported positive results. Other research that did not allow for self-control, also had positive results. However, there are also studies that resulted in no positive shifts that used a self-controlled apparatus (a weighted blanket). The results for hug therapy are all over the map, which is why we need to understand what component(s) of hug therapy cause the hoped-for changes in symptoms, so we can harness that and create a better success rate for this intervention.

Hug Machine’s Effects on Anxiety

Krauss’ (1987) research served as a pilot study (a pilot study is the first of its kind to get the ball rolling on collecting information on this topic). The researchers used anxiety as a variable to test, as most of the literature available at the time the study was conducted discussed hug therapy as a way to calm, and testing anxiety levels when a hug machine is used is an excellent way to determine if there are any calming effects. To determine if there is a particular type of anxiety condition that hug therapy alleviates more than another, the researchers studied two different levels of anxiety, as described below.

Before diving into how this study was conducted, let’s break down the definition of anxiety. Anxiety is a familiar feeling to many, in fact, everyone experiences some form of anxiety at some point in their lives; it’s human nature. Anxiety is defined as a sensation of tension or apprehension caused by a perceived sense of danger (whether actual or fabricated).

How Anxiety was Measured

Objective measurement: wrist pulse for 60 seconds

Before we get to the limitations section, I need to point out that this is NOT the best way to gather physiological data. Skin Conductance or even a wearable heart rate monitor would have been more valid. By having someone count heart rate for 60 seconds there is a lot of room for error.

Subjective Measurement: STAI Forms X-1 and X-2 (State-Trait Anxiety Inventory Self-Evaluation Questionnaire has statements which people use to describe themselves; it’s used to measure how one feels at a particular moment.) I will caveat that there is emerging evidence to suggest that the STAI-10 is flawed.

Form X-1 measured anxiety in the moment
Form X-2 measured if anxiety was a personality trait

Who Used the Hug Machine in This Study?

From a college campus, 78 students were screened utilizing the STAI Form X-2 (described above). Out of all the students who were screened, researchers randomly chose 12 students whose score reflected a high amount of anxiety embedded into their personality and 14 students whose score aligned with a lower amount of anxiety integrated within their personality.

The average age of the students was 21.9 years; There were 20 females, and 3 men; None of the participants had any injuries, pain, or were on any medication.

How were Data Collected for Hug Therapy?

Data were collected during midterms, on purpose, because midterms cause stress, and the researchers wanted there to be present stress. Remember that there were two levels of anxiety being studied: anxiety as a personal trait, and situational anxiety.

Each student participated in the experimental treatment and control so that their data could be compared against themselves. They first completed the STAI Form X-1 (to test their anxiety level before beginning), and then laid on their back inside the Hug’m apparatus pictured below.

Hug Machine
(Krauss, 1987)

The participant laid in the apparatus without using it for exactly 3 minutes, then their pulse data was collected. After the heart rate data were collected, the participant began either the experimental or control condition. This study was counterbalanced, meaning the condition (experimental or control) order was randomized for each participant.

Experimental Condition: The participant controlled the intensity of the hug therapy pressure. The participant remained in the apparatus for 15 minutes, and when that time was up, their pulse data was collected again, and they completed the STAI Form X-1 again.

Control Condition: The participant entered into the same apparatus, but was not able to apply hug therapy pressure. Rather, the participant was enclosed within the device, but in a way where there was no skin contact (other than the participant’s back of course!). Data (the STAI Form X-1 and pulse) were collected at the same time

Can a Hug Machine Reduce Certain Types of Anxiety better than others?

Anxiety In The Moment Results

No significant changes found from within the objective (pulse) data. There was a significant decrease in subjective data (STAI Form X-1 scores), though.

Anxiety As A Personality Trait Results

No significant changes were found in objective (pulse) data; however, there was a significant decrease in STAI Form X-1 scores between the baseline (before the condition was initiated) and after the condition for both experimental and control.

Alright, so that was a bust. The researchers hypothesized that hug therapy would alleviate anxiety and that there would be different results based on how anxious of a personality a person had, but alas, these hypotheses were rejected because the objective and subjective data did not align or they did align and there was just no significance!

So what happened? Here are some theories:

  • It was too hot, as the temperature was not controlled for, which increased the pulse and caused a sensation of anxiety.
  • The participants could not choose where the pressure was applied, thus preventing full control of hug therapy pressure in the way the weight is applied or how much weight is applied. The participants later stated that they felt most of the pressure on their thighs/ legs and they would have preferred more pressure on their chest/ shoulder area.
  • Again, the pulses were collected by the primary investigator, and accuracy cannot be verified.
  • Both groups were confined, confinement may be the component that elicits the calming effect, as evidenced by the significant decrease in STAI Form X-1 scores between baseline and post-condition, for both the control and the experimental condition.

The data does show though, that there was a greater significant decrease in pulse scores from baseline to post-condition within the experimental session, so this is evidence that there is some component of hug therapy that does something!

Here’s what the participants had to say about the Hug’m:

Hug Machine responses
(Krauss, 1987)

What Do We Think?

If you guys are like me, then this opened up a can of even more questions. This study doesn’t really answer many of the questions that I prefaced you may have. This study did set-up a solid foundation for future research to examine the mechanisms of action for hug therapy. Stick with us, as we uncover more truths on hug therapy as an intervention for common ailments.

Why do you think hug therapy works for some and not others? Put your thinking cap on and let’s come up with our own hypotheses!


Krauss, K. (1987). The effect of deep pressure touch on anxiety. The American Journal of Occupational Therapy, 41(6), 366-373.


Veronica is a mental health professional who is pursuing a doctorate in Clinical Psychology. She has earned her master’s degree in Clinical Mental Health Counseling and now provides therapy to children and youth in the community agency setting. She has been a part of several studies withiфn the field of psychology, including cognitive psychology, sports psychology, and health psychology. Her current research interests revolve around utilizing mindfulness meditation techniques and how they can impact the health of individuals in various socio-economic settings. She also has research interests revolving around developing and implementing interventions to aid in recovery from substance abuse within the primary care setting.

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