Q 7 Med 1996; 89:313-317
Commentary
QJM
The state of hypnosis: evidence and applications
J. GRUZELIER
From the Department of Psychiatry, Charing Cross and Westminster Medical School, London,
UK
Thoughtful clinicians have always believed that the
alterations in brain function associated with hypnosis
would one day come to be defined. This belief is
inherent in the now outmoded concept 'hypnotic
trance', and was encouraged by the sometimes
uncontrolled observations of physical changes
brought about by hypnosis. These have included
relief from pain, anaesthesia, changes in the skin's
allergen hypersensitivity response, reduction in the
inflammatory responses to burns, control of the rate
of blood coagulation and so forth. 1 " 4 The absence of
proof of reliable alterations in brain activity from
mid-century psychophysiological studies, however,
gave backing to the psychosocial theories of imaginative participation and role-playing, which have
dominated scientific thinking until recently. Over the
past decade, advances have been made in delineating systematic changes associated with hypnosis.
What is more, in the prehypnotic state, highsusceptibility hypnotic subjects have shown neurophysiological differentiation from those with low
susceptibility. Whilst there is no doubt that in the
clinical context a patient must be a willing participant
in hypnosis, recent work suggests that to say that the
influence of hypnosis on pain, blood coagulation,
inflammatory responses, removal of warts, etc. is
simply the result of role-playing or other psychosocial
dynamics, is naive.
This recent change in orientation of hypnosis
theories is largely a consequence of more informed
approaches to the complexities of brain systems, and
greater rigour in the application of scientific methodology and experimental design. Individual differences in hypnosis susceptibility, glaringly obvious
since the technique's discovery a century ago, have
been of particular use here, as responder and nonresponder groups can be selected a priori. We can
be thankful in this selection for the development of
reliable and valid scales of hypnotic susceptibility
such as those from Harvard and Stanford.5'6 The state
and trait nature of hypnotic susceptibility7 means,
however, that it is essential to establish the retest
reliability of group assignment; in our studies we
now do this on three occasions, including one that
is concurrent with electrophysiological recording.
During the late 1970s, when we began our
neuropsychophysiological
investigations,
hemispheric specialization theories suggested striking
parallels between hypnosis and right hemisphere
functions. These functions included motor passivity,
an emphasis on sensory images, slow and simple
speech, and emotionally charged memories.8
Hypnosis was thought to enhance right hemispheric
activity, and hypnotically susceptible subjects were
thought to be characterized by a right hemispheric
functional dominance or 'hemisphericity' in the baseline state.9 Our initial results led to the emergence
of an altogether more complex picture. 10 ' 11
At first, we measured sympathetically-mediated
eccrine sweat-gland activity, via electrodermal
responses to a series of tones interspersed throughout
the hypnotic induction. These responses were
recorded bilaterally from the phalanges of the first
and second fingers of each hand. There are strong
limbic system influences on responses to simple
sensory stimuli and their habituation. In hypnotized
high-susceptibles, we found evidence of asymmetries
in responses indicating dominance of right over left
temporal-limbic influences, a finding in line with the
laterality hypothesis. Further, in the baseline state,
high-susceptibles showed asymmetry in the opposite
direction, with left hemisphere dominance. Neither of
these effects were seen in low-susceptibles, and the
right hemisphere dominance was not seen in high-
Address correspondence to Professor J. Gruzelier, Department of Psychiatry, Charing Cross and Westminster Medical
School, St Dunstan's Road, London W6 8RF
© Oxford University Press 1996
314
J. Gruzelier
susceptibles in conditions without hypnosis which
controlled for focussed attention or relaxation.11 These
studies showed that whilst hypnosis produced an
accentuation of right hemispheric influences, highsusceptibles in the prehypnosis state showed asymmetry favouring the left hemisphere, and hypnosis
brought about a reversal of asymmetry. Highsusceptibles did not manifest right hemisphericity.
The importance of the left hemisphere in hypnosis
has been further highlighted by a series of studies of
tactual discrimination, a task involving contralateral
active touch pathways.10'12 In these experiments,
subjects were blindfolded, and objects placed in
each hand were identified tactually. Results confirmed that there was left-hemisphere dominance in
high-susceptibles in the baseline state. With hypnosis,
subjects displayed a decline in left hemisphere
discriminations. These findings were in keeping with
ideas of a lateralized inhibitory process in the left
hemisphere. The salience of this for the hypnotic
process was further emphasized by a correlation
between the relative reduction in haptic processing
speed and the magnitude of the susceptibility score
monitored during the experiment, shown in Figure 1.
In high-susceptibles, both the left hemisphere advantage in the baseline state, and the loss in hypnosis of
this advantage, the magnitude of which correlated
with the level of susceptibility reached, implied that
left hemisphere dynamics were fundamental to the
induction process.
These findings, along with the enhancement of
highright-sided activity
with
hypnosis
in
susceptibles, have been replicated in other measurement modalities including cortical evoked potentials,
-10
EEG, and psychophysical and neuropsychological
tasks.12"16 These studies have also highlighted the
importance of anterior-posterior relations. In hypnosis
there is an inhibition of frontal functions, more so
on the left side than the right, and when the aim is
to induce relaxation with hypnosis, there is an
accentuation of posterior functions, greater in the
right hemisphere.
The importance of frontal inhibition in hypnosis
is exemplified by recent neurophysiological evidence.17 Cortical evoked potentials were measured to
rare tones presented amongst a series of identical
but lower pitched frequent tones. The cortical evoked
potentials of patients with frontal lobe lesions differentiate poorly between the classes of tones.18 This is
reflected in the negative component at around
120 ms post stimulus, a component mirroring frontal
attentional processes. We compared high- and lowsusceptibles prior to hypnosis and at an early and
late stage of the induction. The differences in N120
amplitude between frequent and infrequent tones are
shown in Figure 2. In high-susceptibles, the magnitude of the difference can be seen to decrease
progressively from baseline to hypnosis, so that at
the later stage of induction the N120 components
were similar to those of frontal lobe patients. Note
also that the opposite change in electrocortical
activity is seen in low-susceptibles. They begin
poorly, as would occur with inattention and distractibility, but improve with practice.
This result raises another finding in our studies.
Changes shown by low-susceptibles to instructions
of hypnosis are often in the opposite direction to
those found in high-susceptibles. The significance of
3
4
Hypnotic susceptibility
Figure 1. The correlation between hypnotic susceptibility score and the slowing in right hand/left hemispheric processing
time with hypnosis.
The state of hypnosis
315
HIGH-SUSCEPTIBLES
F4
LOW-SUSCEPTIBLES
F4
Figure 2. Differences in microvolts between cortical evoked potentials for infrequent and frequent tones at baseline (B), at
an early stage of hypnosis induction (H1), and at a later stage (H2). There is progressive loss of discriminability during
hypnosis induction in high-susceptibles (top) and a progressive increase in discriminability in low-susceptibles. Measurements
at central (Cz), frontal (Fz), and frontal left (F3) and right (F4) locations. See text for full description.
these changes can be interpreted as antithetical to
the induction of hypnosis. Firstly, instructions of
hypnosis have lead to activation of the left hemisphere in low-susceptibles, with one experiment
actually describing a reversal from right hemisphere
activation prior to hypnosis.13'15 This left-sided activation contrasts with the inhibition of left-sided functions in high-susceptibles. Secondly, whereas highsusceptibles have shown fast habituation to irrelevant
tones interspersed with the induction, 11 ' 19 lowsusceptibles have shown slower habituation. Slow
habituation is a known accompaniment of anxiety.20
Consideration of the significance of the changes
observed has lead to a neuropsychological translation
of the induction procedure.21"23 The induction of
hypnosis for a novice subject commonly begins with
focussing attention on a small object. This will
engage frontal supervisory attentional systems;24 focal
attention underpinned by left-sided functions, and
broad attention with right-sided systems. Once attention is engaged, the next step is to suggest that
sustaining attention is tiring and that eyelids feel
heavy, with the aim of producing eye closure.
Accordingly once focal attention systems are
engaged, the process of frontal inhibition is set in
train. The shift of activation to the posterior, predomi-
nantly right-sided functions begins, through emphasis
on imagery, emotion, and simplified speech. The
inhibition of frontal functions is compatible with the
suspension of both reality testing and critical analysis
of the instructions of hypnosis, and giving over the
planning of behaviour to the therapist.
Initial studies of other methods of inducing deep
relaxation, such as floatation with restricted environmental stimulation, disclose that these methods fail
to share the hypnosis properties of left-sided (frontal)
inhibition. Right-sided functions, however, may be
enhanced.11'25 Differentiation of hypnosis from states
of physical relaxation has been demonstrated by
having subjects ride a bicycle ergometer while hypnotized, 12 ' 26 a procedure which in our study produced evidence of right-sided enhancement and leftsided inhibition in haptic processing.
This body of evidence of reproducible changes in
brain function with hypnosis is currently being augmented with evidence from functional brain imaging
procedures. These include EEG and metabolic measures.13'27"29 There is also a small body of knowledge
accruing from intracranial recording.30"32
Evidence that hypnosis is, after all, a state of
altered brain function will give new impetus to
research on medical applications. This will encour-
316
J. Gruzelier
age studies to verify important observations of organic
changes and therapeutic benefits, many of which
have awaited controlled investigations and replication. The work above offers markers of the depth of
hypnosis, as well as insight into the processes that
underlie low susceptibility, such as broadened
instead of narrowed attention, or focussed attention
without the ability to suspend reality testing.
Applications of hypnosis to immunology (to mention just one medical field) now warrant a greater
investment of effort. There is virtually unequivocal
evidence that hypnosis can modulate inflammatory
processes such as immediate and delayed skin hypersensitivity reactions to injections of histamine or
tuberculin protein derivative. Pioneering work by
Black and colleagues,1'33 has been replicated, 34 " 36
with one negative study.37 In children, increases in
salivary IgA over baseline have been found with
hypnosis. They were randomly assigned to two
hypnosis groups which differed in imagery content
or to a control group matched for staff interaction.
Only when the imagery content involved specific
suggestions to control salivary immunoglobulins was
the effect of hypnosis observed, raising the importance of imagery content.38
Prophylactic influences on immunity have been
claimed for hypnosis used to ease exam stress in
medical students, as the more hypnotic relaxation
was practised before exams, the higher were helper
T-lymphocyte percentages (over baseline) during
exam time. 39 While an alternative explanation may
reside in personality factors associated with a greater
enthusiasm for hypnosis in those that practised the
most—a range of between 5 and 50 sessions, this
does not necessarily diminish the importance of the
result, or its basis in biological factors. We found in
asymptomatic men at early stages of HIV-1 infection
that there were prospective associations between EEG
and neuropsychological profile on first testing and
immune status (CD4 and CD8 counts) up to 30
months later.40 The neuropsychophysiological profiles associated with good and poor immune status
have been associated with differences in personality
and temperament.41'42 Consistent with this, a liveliness—listlessness dimension has been related to the
hypersensitivity skin reaction.36
A landmark study in the field of cancer research
further illustrates the involvement of hypnosis with
immune functioning. Spiegel et al. 43 showed that in
women with metastatic breast cancer, those that
received hypnosis training for pain relief lived 18
months longer on average than the control group.
As Walker44'45 concluded in a recent review, this
evidence of increased longevity is preliminary; however, the efficacy of hypnosis in improving quality
of life, alleviating pain and distress, and ameliorating
the effects of chemotherapy is beyond doubt.
The application of hypnosis to immunity is in its
infancy, as it is with other medical applications
outside of analgesia, childbirth and psychiatry.
Applications that warrant closer scrutiny involve
psoriasis,46 control of seizures47'48 neurological
rehabilitation, 49 chronic fatigue syndrome,50 rheumatoid arthritis,51 reduction of the inflammatory
response to burns4 and asthma52 to mention a few.
Now that we are equipped with the seeds of
neurophysiological validation, a new era in hypnosis
research is just beginning. Undoubtedly the neurophysiological model requires further elucidation and
refinement, but this can be expected to follow access
to new brain-imaging facilities. We can now acknowledge that hypnosis is indeed a 'state' and redirect
energies earlier spent on the 'state-nonstate' debate.
We have gained neurophysiological insights about
the induction of hypnosis, and in so doing have
developed potential markers of stages in the induction process. Equipped with this knowledge we can
proceed to investigate the therapeutic potential of a
unique, safe and non-invasive psychological therapy.
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