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Table 1 Characteristics of studies included

From: Hypnosis in patients with perceived stress – a systematic review

Authors, Year Sample, Sample Size, Gender, Mean Age (SD, range) Design, Number of Groups, Sample points Type of Intervention Type of Control Condition Outcome Measures Results (Between group differences) Study Quality (Strengths, Limitations)
Barling, NR and Raine, SJ (2005) [41] 60 healthy volunteers (14 males, 46 females)
Mean age 41.5 (range 17–63)
No information about further demographic data in the sample
RCT
Three experimental groups,
one control group
Two sample points:
• pre-test before the intervention
• post-test after three weeks of self-practice
1) PMR
2) PMR + guided imagery (GI)
3) PMR + GI + deep trance (DT) with specific mind-body healing language
Tape with recorded intervention for self-practice
No intervention Burnout Assessment Test (BAT) [60]
Depression Anxiety Stress Scales (DASS) [61]
Saliva Immunoglobulin A (sIGA) by “sucking in their mouth”
• Significant condition effect for change in burnout (F(3, 14) = 8.46, p > 0.001), depression (F(3, 14) = 5.13, p > 0.003), anxiety (F(3, 14) = 6.62, p > 0.001) and stress (F(3, 14) = 4.02, p > 0.01);
• Significant differences in changes in burnout, anxiety, and depression between the control group and the DT group (no p-score reported)
+
One-way analysis of variance (ANOVA)
Multiple regression analyses
-
Small sample size
No information about further demographic data and health-related behaviors in the sample
No information about way of random assignment to the experimental groups
No information about results of post hoc-comparisons between groups
Cardena et al. (2013) [42] 56 healthy volunteers
10 males, 46 females
Mean Age 31.13 (SD = 10.00; range 20–61)
44 students, 11 worked, 1 unemployed
21 participants dropped out
RCT
One experimental group
One control group
Three times of measurement:
1. before the hypnotic intervention
2. after two weeks after the hypnotic intervention for group 1
3. after further two weeks after the hypnotic intervention for group 2
Hypnotic intervention: participants were asked to listen to a recording (length 23 min) at least once a day for 14 days.
The tape script consists of an general induction with a focus on breathing, counting a deepening procedure; imagining of specific place of security, peace, and control; creating a personalized “anchor”, posthypnotic suggestions
Waiting list control group Perceived Stress Scale (PSS) [53]
Shirom-Melamed Burnout Questionnaire (SMBQ) [62]
Ways of Coping Questionnaire (WCQ) [63]
General Health Questionnaire 12 (GHQ-12) [64]
• Less stress (t(33) = -2.751, p < .01) and better overall health (t(22.5) = -3.159, p < .004) in hypnosis than in control group +
precise information about exclusion criteria and way of randomization
ANOVAs
-
Many drop-outs
Gruzelier et al. (2001) [43] 28 volunteer pre-clinical medical students
17 males, 11 females
Mean age 20.1
RCT
one experimental group
one control group
Two sample points
• Baseline: four weeks before examination
• Exam: during the exam period
Group hypnosis three weeks before examinations
Tape with recorded intervention for self-practice
Hypnotic induction: visual fixation, relaxation and deepening exercises, instructions aimed at improving immune function and to mobilise resources by increasing alertness, energy and concentration (length 20 min)
No intervention Lymphocyte counts (CD3, CD4, CD8, CD 8/4%, CD 19, NKC)
Cortisol
Life style questionnaire
Emotional state: scales of tension, calmness, energy and tiredness) [65]
State anxiety scale [66]
Activated and withdrawn personality scales [67]
• Immunological measures: reduction in NK cells with exam stress in controls, non-significant increase with hypnosis (F(2, 25) = 6.03, p < .007);
• Mood: no group differences in mood changes (no F- and p-scores reported);
• ratings of energy higher at exam time in hypnosis than in control group (F(1, 26) = 6.16, p < .01)
-
Small sample size
Some results not reaching significance are reported and interpreted as positive results
Kiecolt-Glaser JK et al. (1986) [44] 34 first-year medical students
22 male, 12 female
Mean age 23.5
RCT
One experimental group
One control group
Two sample points:
1. one month before examination
2. on the day of examinations
Hypnotic/relaxation group during lunch hours; 5–10 sessions in 2.5 weeks before the second blood draw
First hypnotic session: overview of hypnosis, group induction;
Each subsequent session: series of deepening exercises used in the initial session, self-hypnosis, progressive relaxation, autogenic training, various imagery exercises, suggestions for greater relaxation throughout the day and enhanced comprehension and retention of academic material (Sessions lasted 25–40 min);
Written manual that specified the content and order of components within each the sessions and request for daily practice
No intervention Brief Symptom Inventory (BSI) [54]: changes in global stress
State Loneliness Scale [68]
Assessment of the degree of relaxation achieved during each session (self-rating 1–9)
Academic performance
Immunological data
Percentage of helper/inducer cells
Percentage of suppressor/cytotoxic cells
Helper/suppressor-cell ratio
NK activity
Nutritional data: Albumin, TIBC, Transferrin
• BSI: significant increases in anxiety (p < .01), obsessive-compulsive symptomatology (p < .05) and in the global severity index (p < .05) only in no-intervention group
No main effect for group and no group x time interaction in
• Loneliness
• Changes in health-related behaviors
• Academic performance
• Immunological data
• Nutritional data
+
Repeated-measures analyses of variance design
multiple regression analyses
-
Small sample size
Kiecolt-Glaser JK et al. (2001) [45] 34 students who obtained a score of 7 or higher on both scales (HGSHS-A and SHSS-C) among 130 students volunteered for the initial screening session
14 male, 19 female
Mean age 23.48 (SD +/− 1.97)
RCT
One experimental group
One control group
Two sample points:
1. within the first few days of the quarter
2. three days before the first major academic examination of the term
5–10 sessions during lunch hours that began 8 days before the second blood draw
First hypnotic session: overview of hypnosis, group induction;
Each subsequent session: series of deepening exercises used in the initial session, various imagery exercises, suggestions for greater relaxation throughout the day and enhanced comprehension and retention of academic material (sessions lasted 25–40 min);
Written manual that specified the content and order of components within each the sessions and request for daily practice
No intervention Self-rating of anxiety (0–10) prior to each of the group inductions
Current relaxation after completion of group induction
Perceived Stress Scale [53]
Positive and negative Affect Schedule PANAS [69]
New York University Loneliness Scale [70]
Immunological Assays
Blastogenic response to phytohemagglutinin (PHA); blastogenic response to concanavalin A (Con A); T-lymphocytes, NK cells, macrophage/monocytes, IL-1β
No significant group x time interaction, no group effect for
• Stress (PSS) and negative affect (PANAS)
• Loneliness
• Immunological data: stable values for PHA stimulation (F(1, 31) = 4.94, p < .04), Con A concentrations (F(1, 31) = 4.26, p < .05), for CD3 + T-lymphocytes (F(1,31) = 5.76, p < .03)- and CD4+ T-lymphocytes (F(1, 31) = 6.05, p < .03) in hypnosis and declines for control group; no significant group effects or group x time interaction for CD8 + −, NK-cells and IL-1β
-
Small sample size
Naito A et al. (2003) [46] 48 students (39/48 medical students);
22 males, 26 females;
Age range 19–23 years with one participant of 37 years
Participants were paid £30 at the end of the study.
Prospective randomized controlled trial
Three groups
• Stress reduction training with self-hypnosis
• Johrei
• Mock neurofeedback relaxation control
Two sample points:
• Baseline: before training
• Exam: 1–2 months later as exams approached
4 Weekly sessions during a 1-month intervention period
Self-hypnosis training: subjects learnt a Spiegel-type eye-roll for instant relaxation first and then a slower relaxation-type induction; subjects were taught a basic immune imagery, and two anxiety management techniques;
standard tape-recording using a relaxation induction and imagery description and request for self-hypnosis three times a day
Johrei healing method: introduction to Johrei philosophy and the coreprinciples needed such as healing oneself by healing others; the subjects were requested to practice Johrei daily with a partner; the practitioner imagines light entering his body being concentrated through his hands towards the recipient and moves his hands slowly from head down to kidney area without touching the recipient
8 mock neurofeedback sessions over 1 month Self-reported stress [53]
Personalised Emotional Index: practice and mood data
Peripheral blood lymphocytes: CD4+ T cells, CD8+ T cells, CD56+ Natural Killer cell percentages (NK cells) and NK cell cytotoxic activity
Natural Killer cells: increase only in Johrei, no change in hypnosis and relaxation (F(1,33) = 5.86, p = .007)
CD8+ T cells: the extent of increase significant greater in hypnosis than in relaxation, but not than in Johrei (F(1,33) = 3.02, p = .063).
CD4+ T cells: decline only in Johrei, no change in hypnosis and relaxation (F(2, 32) = 4.71, p = .016)
+
Repeated-measures ANOVA followed by paired comparisons with non-parametric tests
-
Small sample size
No information about health-related behaviors in the sample
Due to very small samples it is impossible to draw reliable conclusions of results of ANOVA with three factors
Stanton HE (1989) [47] 40 high school teachers
No information about further demographic data in the sample
Prospective randomized controlled trial
One experimental group
One control group
Three sample points:
• Before treatment
• Immediately after treatment
• 12 months after treatment
4 weekly sessions involving a hypnotic induction and 10 positive suggestions derived from key elements of Rational-Emotive Therapy based on a reformulation of Ellis’s challenges to his clients’ irrational ideas (Ellis and Grieger, 1977)
• 1. Session (1 h): hypnotic training and introduction to the 10 suggestions
• 2.-4. Session (0.5 h): standardized induction (breath, counting, body relaxation, pleasant scene imagery) and five repetitions of the suggestions
4 weekly sessions with discussingstress reduction methods Face Valid Stress Test
Level of reasonable thinking: Teacher Idea Inventory [71]
• Teacher Idea Inventory: significant less irrational thinking in hypnosis than in control group after treatment (F(1, 19) = 32.61, p < .01) and at 12-month follow-up (F(1, 19) = 30.65, p < .01).
• Face Valid Stress Test: significant lower stress level in hypnosis than in control group
at 12-month follow-up (t(19) = 5.08, p < .001)
+
Repeated-measures ANOVA followed by paired comparisons with non-parametric tests
-
Stanton HE (1991) [48] 30 secretaries from a large business firm
Age range 27–43
RCT
One experimental
one control group
Three sample points:
• Before treatment
• Immediately after treatment
• 2 months after treatment
Two sessions (1. 50 min, 2. 25 min) while participants listened to an standardized tape which guided them through five stress-reduction steps:
• physical relaxations induced by concentration upon the breath
• mental calmness induced by imagining the mind as a pond into which one can drop concepts such as calmness, confidence as stones
• disposing of “rubbish” as fears, doubts, and worries down a chute
• removal of a barrier of self-destructive thoughts, fears of failure
• enjoyment of a special place and remake the day
Two sessions of the same duration discussing stress management procedures
(stage 1)
After the 2 months follow-up of the experimental group the control group experienced the same two treatment sessions (stage 2)
Stress thermometer [72]
Anecdotal reports
• Significantly greater stress reduction in hypnosis than in control group immediately after the treatment (Scheffé F(14) = 3.64, p < .01) and at 2-month follow-up (Scheffé F(14) = 3.47, p < .01) +
Repeated measures ANOVA
-
Small sample size
No standardized, validated self-report measures
Whitehouse et al. (1996) [49] 35 first-year medical students
14 male, 21 female
Mean age 24.8
Prospective randomized controlled trial
One experimental group
One control group
Four sampling points:
• Orientation
• Late semester
• Exam stressor,
• Recovery
19-week investigation
Self-hypnosis training condition (n = 21)
14 sessions à 90 min around the noon hour, one day per week
request for self-hypnosis exercises at least 15 min each day.
No treatment
Subjects filled out the same daily diaries
Psychosocial data
Profile of Mood States [73]
Brief Symptom Inventory (BSI) [54]
UCLA Loneliness Scale [74]
Immunologic data
• T, B, monocyte, granulocyte, NK, T4, T8, helper-inducer, and suppressor-inducer cells
• Mitogen-induced lymphocyte stimulation by ConA, PHA and PWM
• BSI: significant less anxiety to exam period in hypnosis than in control group (F(3, 96) = 2.96, p < .05)
No between group differences
• UCLA loneliness scale
• Immunologic data
+
Immunological data: repeated-measures multivariate analyses of variance (MANOVAs)
Psychosocial data: univariate repeated-measures ANOVAs