The Effect of Brief Mindfulness Meditation on Cold-Pressor Induced Pain Responses in Healthy Adults

We hypothesised a 10 minute mindfulness based intervention performed by a novice therapist would have a beneficial effect on pain responses in naive participants. Twenty-four participants were randomly assigned to the control group or mindfulness meditation group. The control group sat quietly for 10 minutes in between two cold pressor tasks. The mindfulness meditation intervention group practiced 10 minutes of mindfulness meditation in between cold-pressor tasks following standardised mindfulness of breathing meditation technique instructions provided by a male investigator. A significant interaction effect was found between anxiety towards pain ratings (pre-inter-vention vs. post-intervention) and intervention (F = 6.29, p = 0.02). There was a significant decrease (t = 4.07, p = 0.002) in anxiety towards pain ratings in the mindfulness meditation group following intervention. A significant interaction effect was found between pain threshold times (pre-intervention vs. post-intervention) and intervention (F = 18.45, p < 0.001). There was a significant increase (t = −4.38, p = 0.001) in pain threshold times in the mindfulness meditation group following intervention. A significant interaction effect was found between pain tolerance times (pre-intervention vs. post- intervention) and intervention (F = 18.34, p < 0.001). A significant increase (t = −4.20, p = 0.001) in pain tolerance times in the mindfulness meditation group following intervention was also found. The results suggest a single 10 minute mindfulness meditation intervention administered by a novice therapist can improve pain tolerance, pain threshold and decrease anxiety towards pain in naïve healthy university aged individuals.


Introduction
An increasing interest in the clinical use of mindfulness meditation has led to a surge in recent research that has indicated mindfulness based interventions to be an effective treatment of numerous physical and psychological illnesses [1]. Although mindfulness based interventions are not standardized, mindfulness can be defined as "a set of techniques designed to encourage deliberate, non-evaluative contact with events that are here and now" [2]. Mindfulness meditation can cultivate awareness of the present moment, maintain attention on a single aspect without bias, and encourage detachment from emotions, thoughts, beliefs and any particular outcome [3].
There is a considerable body of research that supports the benefits of mindfulness meditation on pain [1] [3] [4] [5]. Pain can limit movement, function, motivation and psychological well-being of an individual, which are all key factors in the success of the rehabilitation process [6]. Mindfulness meditation can modulate the experience of pain or improve a patients' ability to cope with pain [6]. Attenuation of pain symptoms is seen in experienced meditators and in subjects after many hours of guided practice by experienced meditators [1]. In the clinical setting, patients will not have access to experienced meditators or the time to participate in lengthy mindfulness based interventions. Limited research has explored whether the beneficial effects of mindfulness meditation demonstrated by experienced meditators or many hours of practice can be seen in untrained individuals after a brief intervention.
Most clinicians will have little to no experience in mindfulness meditation training. Presently, the effects of a brief intervention administered to both genders by a therapist without years of mindfulness meditation training experience are unclear. If a brief mindfulness based intervention can replicate the positive effects on pain shown in experienced meditators and longer mindfulness based interventions it could benefit patients and clinicians attempting to improve patients' rehabilitation process and overall well-being.
Our study examined the effects of a single, brief session of mindfulness meditation on multiple aspects of the pain experience.

Methods
This study was approved by the local ethics committee at the Faculty of Health and Social Sciences, Leeds Beckett University and the Ethical Guidelines of the International Association for the Study of Pain were strictly followed during recruitment and conduct of the experiments which lasted from December 2014 to February 2016.

Participants
A power calculation using Harvard University online calculator (http://hedwig.mgh.harvard.edu/sample_size/size.html) revealed that a total of ty is 90 percent that the study will detect a treatment difference at a two-sided 0.05 significance level, if the true difference between treatments is 1.389 times the standard deviation. To be recruited participants had to be over 18 years of age. All participants completed an eligibility form to ensure they were healthy and pain free. Informed consent was gained from each participant prior to data collection. A self-exclusion screening form was completed by all participants to ensure the absence of factors that could contribute to altered pain perception.
These factors included use of any medication, skin sensation disturbances and previous meditation experience. Following standard convention for the coldpress or task, participants that could maintain their hand in the ice water for 3 minutes were excluded from the study. No participants were excluded from the study. All participants completed the study. The final sample contained twenty-four participants, twelve female participants with the average age of 24.25 (SD = 1.21) and twelve male participants with an average age of 24.58 (SD = 2.11).
The participants were randomly divided into a control group or a mindfulness meditation group containing equal numbers of males and females.

Cold-Pressor Task
The cold pressor-task is a reliable and valid method for inducing pain [7]. It has also been shown to generate a reproducible onset of pain sensation and cause an aching pain of a similar clinical nature and intensity [8] [9]. Every participant was provided a familiarisation session to introduce the cold-pressor task and allow participants to get comfortable with the task. A crib sheet with succinct instructions on how to perform the cold-pressor task was used for every participant and every cycle. The cold-pressor apparatus involved two basins. One contained warm water at 36˚C -37˚C. The other contained cold water and ice between 0˚C -2˚C. Before the cold-pressor task, participants placed their hand in the warm water for 2 minutes to maintain a baseline temperature. Their hand was then moved immediately into the ice water. Participants attempted to keep their hand submerged in the ice water for as long as possible. When the pain could no longer be tolerated, participants removed their hand from the ice water.

Mindfulness Meditation Intervention
The mindfulness meditation instructions were read to each participant word for word by the same researcher. The researcher did not have any previous mindfulness meditation training experience. The instructions represent a brief introduction to the mindfulness of breathing mediation technique where an individual focuses their attention and awareness toward their own breathing. This simple practice is based upon traditional Buddhist teachings from the Anapanasati Sutta [10]. After the instructions were read, the participants were encouraged to meditate for the remaining 10 minutes. The mindfulness meditation instructions were as follows: • You might feel funny for a bit. If you need to open your eyes at any point feel free but bring your attention back to the mindfulness meditation.
• Once I am done with the instructions, I will leave you to mindfully meditate for 10 minutes.

Procedure
The study was led by the same researcher in the same University laboratory room for all participants. Participants were randomly allocated to the control intervention or mindfulness meditation intervention groups. Participants in both groups underwent a pre-intervention cycle of the cold-pressor task and a post-intervention cycle of the cold-pressor task separated by a 10 minute interlude. The control intervention group sat quietly for 10 minutes in between coldpressor tasks. The mindfulness meditation intervention group practiced 10 minutes of mindfulness meditation following brief instructions provided by the researcher in between cold-pressor tasks. The 10 minute interval between coldpressor task interventions assisted to control for diffuse noxious inhibitory control, a form of pain control where the perception of one painful stimulus inhibits the perception of a second painful stimulus for an analgesic effect [11]. All participants were blinded to the intervention others participants received and the expected outcomes.

Data Collection
During the experiment the following measurements were collected pre-intervention and post-intervention for both the control and mindfulness meditation groups: Anxiety towards pain: This subjective measurement is the degree of anxiety towards pain. Each participant marked the degree of perceived anxiety prior to each cold-pressor task on a line scaled from 0 mm "no anxiety" to 100 mm "worst anxiety".
Pain Threshold: This objective measurement is the length of time it took for the first sensation of pain after participants submerged their hand in the ice water. Participants stated "pain" verbally on first sensation of pain. The time was recorded using a stop watch.
Pain Tolerance: This objective measurement is the length of time participants were able to keep their hand submerged in the ice water. The time was recorded using a stop watch.
Pain Intensity: This subjective measurement is the degree of perceived pain intensity. Each participant marked the degree of perceived pain intensity on a line scaled from 0 mm "no pain" to 100 mm "worst pain" as soon as they removed their hand from the ice water.
Pain Unpleasantness: This subjective measurement is the degree of perceived pain unpleasantness. Each participant marked the degree of perceived pain unpleasantness on a line scaled from 0 mm "not unpleasant" to 100 mm "extremely unpleasant" as soon as they removed their hand from the ice water. Table 1 lists the descriptive statistics of all the measured variables for both intervention groups. Pre-intervention measures did not differ significantly (all p> 0.1) between intervention groups except for anxiety towards pain ratings. Preintervention anxiety towards pain was significantly higher (p < 0.05) in the mindfulness meditation group compared to the control group. Only pre-intervention pain tolerance times were significantly higher in males compared to females (p < 0.05). All other measurements did not differ significantly (all p > 0.05).

Anxiety towards Pain
Despite the initial difference in anxiety towards pain ratings, repeated-measures analysis of variance (ANOVA) showed a significant main effect for anxiety towards pain across both interventions (F(1,22) = 10.57, p < 0.01). There was also a significant interaction effect for anxiety towards pain x intervention (F(1,22) = 6.29, p < 0.05). A paired-sample t-test was conducted for both the control and mindfulness meditation group due to the significant interaction effect. A significant decrease (t(11) = 4.07, p < 0.005) in anxiety towards pain ratings was demonstrated in the mindfulness meditation group. Anxiety towards pain ratings did not change significantly in the control group (t(11) = 0.53, p > 0.5) (see Figure 1).

Pain Intensity and Pain Unpleasantness
ANOVA analysis showed there was neither significant main effect nor interaction effect between interventions for both pain intensity and pain unpleasantness.

Discussion
The results suggest a single 10 minute mindfulness meditation intervention administered by a novice therapist can improve pain tolerance, pain threshold and decrease anxiety towards pain in naive healthy university aged individuals. The findings demonstrate a potential improvement in the ability to cope with a painful experience after brief mindfulness meditation irrespective of the degree of perceived pain intensity or unpleasantness. Ease of application and cost effectiveness of brief mindfulness meditation may also make it a viable alternative analgesic option for a range of pain management situations (i.e. prior to painful rehabilitative activity) and settings (i.e. clinical waiting rooms).
Our results confirmed earlier reports of Zeidan et al. [5] who demonstrated effective reduction of anxiety, pain unpleasantness and pain intensity ratings following a 3 day mindfulness meditation intervention. However, the intervention in the study of Zeidan et al. [5] required a substantial time commitment from participants and training sessions were conducted by an instructor with more than 10 years of trained mindfulness meditation experience. In a later improvement Liu et al. [12] designed a 25-minute mindfulness based training session consisting of 15 minutes of pre-recorded mindfulness meditation instruction,   followed by 10 minutes of practice. This brief intervention revealed a significant improvement in pain tolerance and distress ratings (p < 0.05) but no significant difference in pain intensity ratings, partially replicating findings of longer inter-ventions [12]. However, only female participants were examined and the study lacked a comparable control group. This intervention also lacked patient-therapist interaction since pre-recorded mindfulness instruction was used.
Clearly, more research is needed to include short mindfulness intervention in the arsenal of pain therapists. The significant results presented here should be approached with caution as the sample size was small and the control group had 10 minutes similar to the intervention group so they may be also had a chance to reflect on their experience. More significantly, all participants were young healthy pain-free students. This research suggested that brief mindfulness intervention can be of benefit in pain relief but should be explored more in clinical setting on chronic pain patients.