Clinical Research on the Psychological Effects of Sweating: 1954 to 2004
Research attempting to measure the psychological effects of sweating is rare, especially when it comes to randomized controlled studies. Searching the following data bases (PsychInfo, Eric, Medline), there were no research investigations on the psychological effects of sweating procedures prior to the 1970s. And since the 1970s, the investigations undertaken have been a hodgepodge of different topics rather than a coherent, solid accumulation of knowledge concerning the psychological effects of sweating procedures. Since there is such a wide variability in the literature on the psychological effects of sweating procedures, this review presents a summary in chronological order.
The scientific study of sweating procedures has been almost entirely focused on the Finnish sauna as opposed to other forms, such as the American Indian sweat lodge, Russian bania, Turkish hammam, etc.
In 1954, Dr. Covalt, a physician, wrote “Sauna Baths – A Preliminary Report”. In it, he reported an absence of the sauna in medical literature. His literature review conducted through the Library of Congress resulted in ten reports: Six from Germany; three from Switzerland; and, one from Sweden (Covalt, 1954). These reports, spanning from 1938 to 1950, investigated the physiological effects of sauna bathing. Covalt, calling for a replication of European findings in the United States, conducted a study with five healthy women taking weekly saunas for twelve weeks. In addition to reporting the results of basic measures of body weight, blood pressure, and body temperature, Covalt reported that the sauna caused the women to experience a sense of well-being.
The next study on the psychological effects of sweating does not appear until 1972. Kuusinen and Markuu investigated the immediate aftereffects of the Finnish sauna on psychomotor performance and mood with 20 males. The results indicated that the effects of sauna bathing on performance that required rapid and adequate psychomotor adjustment did not differ from those of merely washing oneself. Slight differential effects on mood were discovered with decreases in anxiety and hostility (Kuusinen & Markuu, 1972).
In another 1970s experiment, this time with five young healthy males, the participants were exposed to a 90º C sauna as three ten-minute sessions separated by rest periods at room temperature in between (Putkonen & Elomma, 1976). During the subsequent night their EEGs were recorded and the recordings compared to their sleep-EEGs taken without a preceding sauna bath. The results were that the post-sauna sleep was deeper; during the first third of the recording period, or the first two hours, there was 72% more delta wave sleep than in the control recordings (1976).
No experimental studies were found to have occurred in the 1980s. Sorri (1988) wrote a psychoanalytic view of sauna bathing and described it as follows (p.236):
Sauna bathing is a pleasant and relaxing experience that combines psychic, physical and social pleasures. A person’s inner feelings about sauna bathing, its essential components are mainly unconscious. The sauna bath reduces the aggressive behavior and enables bathers to forget the commonplace pressures of everyday life. The sauna evokes memories of childhood development, awakening feelings of maternal warmth and paternal power in the bather. The sauna is a positive mental health resource, even though its effects are transitory.
Frankva and Franek (1990) found significant positive effects of sauna baths on immediate mental states for both men and women (N = 100). These effects included improvements in mental satisfaction, energy, relaxation, frustration, and anxiety. Limitations of this study included that all the participants were regular sauna users (1 year minimum) and the absence of a comparison group.
In 2000, Colmant and Merta completed the first investigation into combining group counseling with group sweating with four adolescent boys with disruptive behavior disorders. They suggested that one way in which intense heat exposure is complimentary to the counseling process is that “sweat therapy” offers physiological and psychological stress whereby the patient is provided psychosocial support to learn better coping (2000). The heat during sweat therapy was described as a dynamic force. They explained that, for the first ten minutes the average participant will likely experience the heat as pleasurable but this gradually changes to an effort of endurance as time passes. When the experience changes to an effort of endurance, those with problems of frustration tolerance are especially challenged (Colmant, 2003). Similarities between anxiety/anger provoking situations and sauna are that body temperature rises, heart rate is increased, sweating is induced, and negative self-talk begins, thus, people with problems of aggression or anxiety who have difficulty remaining calm and/or prosocial when in a physiologically escalated state may especially benefit from sweat therapy. Recent research supports that those with higher neurotic personality traits have greater difficulty coping with heat stress (LeBlanc, Ducharme, Pasto, & Tompson, 2003).
LeBlanc, Ducharme, Pasto, and Tompson (2003) investigated the relationship of personality traits to people’s responses to warm and cold environments with 20 young healthy adults. The personality measure used was the Big Five Personality Inventory (BFPI). Higher scores on each of the five scales are related to higher self-reported levels of extraversion, agreeableness, conscientiousness, neuroticism and openness. For both the cold and the hot environments, the researchers found that people who scored high for neuroticism (tendency to be anxious, fearful, sensitive, and self-critical) had both a higher discomfort rate and a lower autonomic nervous system (ANS) response. In other words, when in the cold environment (10º C) they reported it to be highly uncomfortable and shivered less than normals. In the hot environment (40º C), they found it highly uncomfortable and sweated less.
Since 1997, Dr. Emilio Gutierrez, a clinical psychologist at the University of Santiago in Spain, has been investigating the use of heat treatment for people with anorexia nervosa (AN). Three types of heat treatment that Dr. Gutierrez and his colleagues are investigating include continuous exposure to a warm environment, wearing a thermal vest, and sauna. Heat treatment was developed with the specific aim of helping patients to control strenuous exercising and other manifestations of hyperactivity. Excessive activity is a recurrent characteristic observed in people with AN since the first modern descriptions of the illness (Gutierrez et al. 2002).
The main instigation for the development of heat-treatment for hyperactivity was an extrapolation from animal research where the effect of ambient temperature (AT) on the behavior of rats exposed to restricted feeding schedules has been investigated. This research describes decrease in feeding behavior and the "self-starvation" observed in rats when the animals are simultaneously exposed to a restricted feeding schedule and given free access to an activity wheel (Routtenberg & Kuznesof, 1967). Because of the numerous parallels with behavioral features of AN patients (such as hyperactivity, hypothermia, self-starvation, and weight loss), this animal model has been proposed as a potentially useful analogy of AN (Epling & Pierce, 1996). In this research, it is suggested that hyperactivity in rats (wheel running) serves a compensatory function in support of thermoregulatory homeostasis, impaired by loss of weight brought about by the interaction between restrictive food schedule and physical activity (Sherwin, 1998). However, the interaction between restricted feeding and activity in the rats is heavily dependent on ambient temperature. Just running the experiment 6 °C above standard temperature is sufficient to inhibit excessive running in the rats. Accordingly, they do not lose weight, do not self-starve, and survive the experiment (Lambert, 1993). In warmer temperatures, Rats improve their meal efficiency and gain weight in spite of the experimental conditions of restricted feeding and free access to the running wheel (Morrow et al. 1997).
Gutierrez et al. (2002) also found sauna use suspiciously not listed in the medical literature as a weight loss strategy used in AN. They explain that the absence of sauna use in AN is unusual because it is very effective at causing rapid fluid loss like other commonly used weight loss methods in AN such as diuretic and purgative abuse. These researchers speculate that sauna use may prevent people from developing the full-blown syndrome and may accelerate their recovery. The researchers describe their successful clinical experience and case study using a sauna with AN. They report that as activity receded, the patients did not report anxiety, depression, or other unpleasant experiences, but on the contrary they repeatedly emphasized the calming and relaxing effect of heat. These psychological changes were followed by a progressive normalization of eating. Furthermore, those changes were maintained during follow-up after the discontinuation of sauna use (2002). However, Gutierrez et al. have not yet produced a randomized controlled study using sauna for patients with AN. In an interview with Dr. Emilio Gutierrez in July 2004, he made the following comments (Colmant, 2004):
Colmant: Can you say more about your plans for a study using a sauna with people with AN? One of the things I am curious about is if you are planning a randomized controlled study using a sauna?
Dr. Gutierrez: Of course, this is the study I am most interested to perform. However, I can’t give you a definite answer at the moment. Actually, I am in Vancouver to check out this possibility. I know that there would be a lot of difficulties to perform the ‘first’ study with sauna and AN patients. The ethics committee could pose a lot of difficulties. Four years ago, I managed to send Prof. Peter Beumont in Sydney, an infrared sauna. This was a very expensive enterprise and the sauna is still there. Regretfully, after the death of Prof. Peter Beumont, I think that this sauna cabin will never be used. It is easier to do trials with new drugs, no matter how ineffective they happened to be, or how feeble the theoretical foundation could be. A problem with the sauna is that, in comparison with drugs, it seems half mysterious, half esoteric. Probably, we will need to move slowly and accumulate more direct and indirect evidence about the beneficial, preventative, protective effect of heat, and their risks too. An important clue in this respect will be what Anu Vähäsoini will find in her study in Finland about the current practice of sauna use by real AN patients. The whole idea about the role of heat in the treatment of AN will then be more ample than just performing a one-shot study (sauna, or whatever other device). Probably our next step after the first randomized trial with thermal vests here in Vancouver, will be a dose-response study with this strategy of heat application.
One of the most consistent descriptions of the effects of sauna is that it causes feelings of relaxation and stress relief (Colmant & Merta, 2000; Gutierrez, Vazquez, & Beumont, 2002; Sorri, 1988; and Sudakov, Sinitchkin, & Khasanov, 1988). Specific descriptions concerning the use of intense sweating in counseling include that intense heat exposure creates an altered state of consciousness for the participant, creates a challenging activity in which to improve coping, and requires no movement and therefore lends itself well to process facilitation.
Some writers have described the sweating experience as creating an altered state of consciousness (ASC) for the participant. An ASC is defined as a transient state characterized by time distortion, disinhibition from social constraints, altered sense of self, or a change in focused attention. Typical examples of activities thought to cause an ASC include dreaming, endurance running, meditation, daydreaming, hypnosis, and various drug-induced states (Dietrich, 2003). Michael Winkelman, an anthropologist from the University of Arizona, describes group sweating as a shamanic practice used worldwide to promote ASCs (2000). Barbara Kerr, Ph.D. is a professor of counseling psychology at Arizona State University and recipient of the American Psychological Association Presidential Citation. She is a leader in the fields of Gender and Giftedness, Spiritual Intelligence, Creativity, and Counseling Gifted Students. In her most recent book, Letters to a Medicine Man: The shaping of spiritual intelligence, she wrote extensively about her experience using the American Indian sweat lodge (2002). In an interview in February, 2004 Dr. Kerr made the following comments about the role of the heat in the sweat lodge in psychological healing:
Eason: What is the role of the heat in the sweat lodge in psychological healing, from your perspective?
Dr. Kerr: It's just a vehicle. I think that the heat moves people into an altered state much more rapidly than other techniques. It raises arousal level and when people are in high state of arousal, when they are a bit frightened and uncomfortable they tend to be more open to interpretations that will help resolve that arousal. They can attribute their resolution of the arousal to that interpretation, so that in the sweat lodge, within 5 minutes, people are sweating and hot and kind of scared and in that state, they are looking - remember it is dark, so in that state of almost no stimulation except the heat and the closeness, they are looking for a way of resolving their anxiety and fear. Often, the particular prayers and interpretations that are made give the person a way out, a way out of that state of fear and arousal, so that if something as simple as telling a story of Atomi and the 49 warriors, there is an interpretation-at the end of the story- it says: and so we realize that Atomi's warriors of fear and doubt are merely illusions. This statement of fear and doubt are illusions if it is timed exactly right, the person has a euphoria sometimes, a catharsis where they recognize not only the fear of the sweat lodge, the fear of the heat and darkness. Somehow it generalizes to their other fears and they recognize their fears are illusionary in their lives.
Eason: Fear becomes a very powerful emotion.
Dr. Kerr: In a way we turn fear back on itself, we turn Atomi's warriors and get them into retreat by showing the illusionary nature of fear. We also show we have control. We have power to control our fear. People learn that the singing and drumming also helps that and they learn a number of ways of managing their fear. In therapy of course, there are procedures like Gestalt techniques that are very confrontive that do the same thing. They raise arousal level to the point the people are just casting around looking for some way for resolving this horrible state that they are in, in fear. And when an interpretation comes around they will often grab at it.
Eason: You mentioned singing and dancing, are they other ways, that you are aware of that you think have the same power that heat, singing and dancing have?
Dr. Kerr: Yes. I think any kind of rigors that we expose ourselves to, again within a safe environment, that essentially make our brain chemicals and our body more ready for change. That is why fasting tends to put people in very receptive states, fasting, various kinds of deprivation and rigors such as running, dancing, these kinds of things. Of course, the dancing is changing heart rate and that sort of thing. So, some rigors sort of just prepare us to be more receptive and some rigors that we encounter just flip the consciousness. One thing I am very interested in looking at is the flip from sympathetic to parasympathetic, there seems to be some sort of move from sympathetic to parasympathetic response that seems to be a very fertile and fruitful time for change to occur.
Conceptualizing the sweating experience as an altered state of consciousness, however, creates additional assumptions and many complexities in terms measurement. The existence of ASCs is still considered controversial and research with ASCs is typically conducted with complex neurological instruments that are costly and require highly specialized training such as in electrophysiological and neuroimaging. Conceptualizing the sweating experience simply as a form of exercise is more parsimonious, makes sense and seems to have better practicality.
In a study with 24 college students exploring the effects of sweat therapy on group dynamics and affect, the researchers attempted to measure the effects of the sweating experience using the Critical Incidents Questionnaire (CIQ) and the Positive and Negative Affect Scale (PANAS) (Colmant, Eason, Winterowd, Jacobs, & Cashel, in press). For both the men and women’s sweat groups, statements classified as Experiential Features on the CIQ indicated that the sweating process promoted relaxation, a relief from stress, and/or a feeling of accomplishment. In fact, the sweating process was noted by participants as one of the most important aspects of their experience as the sweating process was the second most frequently identified factor by women after Acceptance/Cohesion and ranked third for men after Acceptance and Interpersonal Action. Relaxation, stress relief, and/or a feeling of accomplishment were not reported as benefits by any of the non-sweat participants on the CIQ.
These findings, however, were not supported by the results with the PANAS. Participants completed the PANAS at the end of each session. The PANAS measures positive and negative feelings and emotions. It consists of ten positive adjectives and ten negative adjectives. Positive Affect (PA) reflects the extent to which a person feels enthusiastic, active, and alert. In contrast, Negative Affect (NA) is a general dimension of subjective distress and unpleasurable engagement that, “subsumes a variety of aversive mood states,” (Watson et al., p. 1063). Participants are asked to rate the adjectives based on how they feel using a five-point Likert scale (1 = Very Slightly or Not At All, 5 = Extremely). The PANAS is scored by totaling one score for the ten positive adjectives and one score for the ten negative adjectives.
No differences were found between sweat and non-sweat groups in the experience of affect. Timing of administration of the PANAS may have been problematic. In this study, participants were tested immediately after each session and were compared for affect measured after the second session to affect measured after the seventh session. Since measures were not taken before each session, acute changes in affect were not ascertained. Colmant et al. (in press) recommended that it will be important for future researchers to measure subjects’ response at multiple times: before-sweat, during-sweat, and post-sweat. From clinical experience with sweat therapy, people often report feeling their best about an hour after the experience, report sleeping better, and experiencing noticeable positive effects into the following day. In addition, the PANAS may not be sufficiently sensitive to effects of the sweating experience on affect. The domains of the PANAS have been criticized as too restrictive and containing items irrelevant to intense physical activity (McAuley & Courneya, 1994; Gauvin & Rejeski, 1993). Measures of acute exercise-induced changes in affect may be more sensitive to the sweating experience.
McAuley and Courneya (1994) and Gauvin and Rejeski (1993) argue that existing measures of mood and affect such as the POMS and the PANAS do not do well to measure the stimulus properties of the subjective experiences unique to physical activity. McAuley and Courneya argue that the PANAS is problematic from both a conceptual and theoretical perspective as a result of it being a single-item affect scale that presumes that affect is simply bipolar and unidimensional (1994). From their research, the stimulus properties of physical activity include Revitalization, Tranquility, Positive Engagement, and Physical Exhaustion (Gauvin & Rejeski, 1993) and Positive Well-Being, Psychological Distress, and Fatigue (McAuley & Courneya, 1994). The Exercise Induced Feeling Inventory (EIFI) measures Revitalization, Tranquility, Positive Engagement, and Physical Exhaustion (Gauvin & Rejeski, 1993). The Subjective Exercise Experiences Scale (SEES) measures Positive Well-Being, Psychological Distress, and Fatigue (McAuley & Courneya, 1994). Both the EIFI and the SEES were designed to (a) be employed during activity if necessary, (b) be capable of being used in multiple administrations, and (c) be sufficiently sensitive to experiences unique to physical activity (Gauvin, L. & Spence, 1998).
Thinking about intense heat exposure through use of a sauna, steam room, or sweat lodge as a form of exercise provides a useful analogy. The definition of “Exercise”, according to the American Heritage Dictionary, includes “activity that requires physical or mental exertion, especially when performed to develop or maintain fitness” (1976, p. 459). The sweating experience produces profound physiological changes and perceptions of physical symptoms. Both exercise and sauna cause the stimulation of the sympathetic nervous system and the activation of the hypothalamus-pituitary-adrenal hormonal axis and both cause an increase in noradrenaline (E. Guiterrez, personal communication, July13, 2004). However, there does seem to be some notable differences between exercise and the effects of sweating procedures. Unlike in typical exercise activities, sauna causes an increase in β-endorphins and does not increase the concentration of adrenaline in the blood stream (E. Guiterrrez, personal communication, July13, 2004). Sauna also causes muscle relaxation, whereas, typical exercise activities require muscle tension and the movement of large muscle groups.
In recent years, there has been a growing recognition of the role of physical activity in the maintenance and promotion of mental health, psychological well-being, and health-related quality of life (Gauvin & Spence, 1998). Gauvin and Spence explain that, in this regard, a focal point for researchers has been to study the outcomes of acute bouts of physical activity on transient psychological states (1998). They report that, “the literature shows that acute vigorous physical activity results in decreased state anxiety and depression and improved feelings of energy, calmness, and hedonic tone,” (Gauvin & Spence, 1998, p. 325). Furthermore, other researchers have demonstrated that single bouts of physical activity can dampen the reactivity associated with psychosocial stressors that may contribute to the etiology of cardiovascular disease (Blumenthal et al. 1991).
A unique feature of sweating compared to other forms of exercise is that it does not require movement. The fact that sweating does not require movement makes it especially conducive to being combined with counseling and psychotherapy. A noteworthy difference between sweat therapy and experiential activities used in adventure therapy such as ropes is that in ropes, processing mainly takes place after the challenging activity and in the sweat therapy sessions, processing takes place during the challenging activity. In ropes, therapist facilitated processing typically takes place initially with goal-setting and presentation of activities, immediately after an activity in the form of debriefing, and at the end of the session to provide consolidation of learning, evaluation of the group, and closure (Blanchard, 1993). In sweat therapy sessions, therapist facilitated processing takes place while the participants face the challenging activity of enduring the heat. This provides the opportunity for the therapist and other group members to better enter into an individual’s psychology while they struggle. This opportunity can be especially advantageous when working with people who often minimize, deny, or have poor insight. For example, a question stated in the present tense such as, “What are you thinking about right now?” often produces more elaborate information than one asked in the past tense. Few rigorous physical activities are conducive to therapist facilitated processing while an individual is engaged in the activity due to the individual’s attention being required to safely perform the necessary movements. Another advantage to group sweating being a strenuous physical activity that does not require movement is that many people often excluded from participating in activities like ropes, rock climbing, or backpacking because of ambulatory problems can participate in sweat therapy. Heart problems and acute respiratory diseases are of the few conditions that might make intense sweating medically contraindicated.
Research currently underway at Oklahoma State University attempts to replicate the Colmant et al. (in press) study on the effects of sweat therapy on group therapeutic factors and feeling states with a larger sample (N = 85), better control including comparable session times between sweat and non-sweat groups, and a more effective measurement strategy by including more sensitive and comprehensive measures (Therapeutic Factors Inventory, Exercise Induced Feeling Inventory, & Subjective Exercise Experiences Scale) and a repeated measures design (pre – during –post – 2 hr post –next day post) with feeling state measures. The purpose of this study is to investigate the effects of sweat therapy on group therapeutic factors and feeling states with a group of college students. The feeling states investigated will include Revitalization, Tranquility, Positive Engagement, Physical Exhaustion, Positive Well-Being, Psychological Distress, and Fatigue.
In summary, the previous literature on the psychological effects of sweating procedures is sketchy and includes a wide variety of topics. There is a lack of randomized controlled studies and many of the studies were conducted with a small number of participants and lacked adequate comparison groups. However, there have been some interesting findings that have important implications for therapeutic and preventive mental health purposes. These findings include that sweating promotes positive effects on sleep, mood and affect, and on hyperactivity, specifically for people with anorexia nervosa. One of the most consistent descriptions is that sweating facilitates relaxation and stress relief. Preliminary research with sweat therapy finds the process of group sweating to be complimentary to group counseling. There is a strong need for replication of studies to better solidify these findings. Utilizing measures of acute exercise-induced changes in affect offers a pragmatic approach at this point in the development of investigating the psychological effects of sweating procedures.
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