Medical researchers have long known that placebo treatments
can produce real effects, such as pain relief. Personality traits are also
known to influence a person’s response to treatments for certain conditions. A
recent study
has found that personality traits appear to influence how strongly a person
responds to a placebo treatment for pain. Personality traits associated with
self-control and the regulation of anger in particular were associated with
greater pain relief. This raises the possibility that improving a person’s
self-control and ability to manage anger could also improve their ability to
control pain.
Image courtesy of Michal Marcol at FreeDigitalPhotos.net
In this study, volunteers received a series of four
injections while receiving PET scans to monitor brain activity (Peciña et al., 2012). Two of the injections
were designed to be painless and the other two were intended to be quite
painful. Participants were not told in advance which injection they would
receive so as not to bias their expectations. After receiving one of the
painful injections they were administered a substance that they were told would
relieve the pain but which was actually an inert saline solution with no analgesic
properties. This placebo treatment produced a significant reduction in pain.
Pain was rated both subjectively (by self-ratings of pain intensity) and
objectively (changes in opioid receptor function observed through PET scans).
Pain relief tended to be stronger in participants who rated themselves higher
in the personality traits of ego resiliency and agreeableness and lower in
neuroticism. Agreeableness and neuroticism each consist of a number of narrower
facets that were also examined. The facets that predicted placebo response most
strongly were high altruism and straightforwardness (facets of agreeableness)
and low angry hostility (a neuroticism facet that is also related to low
agreeableness).
Neuroticism is a trait associated with negative emotionality
People high in neuroticism tend to report more physical symptoms and
complaints, such as headaches and muscle tension and so on, than less neurotic
individuals (Ode & Robinson, 2007).
People high in neuroticism cope with pain more poorly than other people
probably because they tend to over-react emotionally. There is evidence linking
physical pain and negative emotions as neuroimaging studies have found that
endogenous opioid activity in a number of brain regions modulate both the
experience of physical pain and of negative emotions. Angry hostility was the
neuroticism facet that most strongly predicted (poor) placebo response in this
study. The authors stated that there is research evidence linking anger to
lower opioid receptor system functioning so this result was not surprising (Peciña, et al., 2012).
Agreeableness is an interpersonal trait associated with
cooperativeness and concern for others. The authors of the study noted that
patients who are highly agreeable tend to have a better relationship with their
doctors as they take a frank and collaborative approach. Agreeable patients may
therefore respond more readily to treatment, even if the treatment is a
placebo. Additionally, agreeableness has been linked to placebo responses to
acupuncture. They also noted that PET scans showed that the placebo response
(that is, opioid receptor function) occurred in brain regions that respond to
observing pain in others, and therefore play a role in empathy. Agreeable
people tend to be empathetic to the suffering of others, so this overlap
between the brain regions associated with the placebo response and with empathy
might help explain the connection with agreeableness, particularly the altruism
facet.
Altruism is associated with selflessness and self-sacrifice
for the benefit of others. Perhaps people who are self-sacrificing are better
able to control pain? Perhaps, being able to suppress pain when needed
facilitates self-sacrifice because the pain and inconvenience of foregoing
one’s own interests for the benefit of another person becomes easier to bear.
Straightforwardness, the other agreeableness facet that predicted the placebo
response, is associated with honesty and openness in one’s communication with
others. One possible explanation for its connection with the placebo effect is
that people who are naturally honest may have been more likely to believe the
researcher when they were told they were being given a treatment that would
provide pain relief.
Agreeableness is also related to effortful self-control, in
particular the ability to control the expression of anger (Ode & Robinson, 2007). As noted
previously, anger has been linked to the opioid system, so this may another
reason that agreeableness is linked to the placebo effect. Another personality
trait linked to both self-control and the placebo effect is ego-resiliency.
Ego-resiliency might be described
as flexibility in self-control. That is, a person can inhibit their impulses
when required by the situation, and yet also allow him or herself to be
spontaneous and uninhibited when this is permitted. That is, the person can
adapt their level of self-expression to the demands of the situation. This in
contrast to people who are either chronically over-controlled – that is, unable
to loosen up when they need to – or under-controlled, unable to restrain their
impulses when expected to do so. Ego-resiliency assists a person in adapting to
stress and adversity as over-controlled individuals tend to respond in a stiff,
repetitive manner, whereas under-controlled people respond in a chaotic and
unfocused manner (Letzring, Block, & Funder,
2005). The researchers argue that ego-resiliency is associated
with positive emotions and adaptive changes in areas of the brain related to
reward and emotional processing. Specifically, there is evidence that this
trait may be associated with lower levels of activation of the dopamine system
during expectation of reward, and lower levels of dopamine in turn has been
associated with greater activation of endogenous opioid receptors during a
painful stressor (Peciña, et al., 2012).
The findings that the placebo effect is linked to
personality traits associated with self-control, i.e. agreeableness and
ego-resiliency, suggests that the placebo effect is influenced by a person’s
capacity to regulate how they respond to adverse experiences. Even though the
placebo effect would seem to be outside of conscious awareness, it appears that
people who have developed the ability to regulate their emotions may also have
a greater ability to regulate pain. This might be because the brain regions
that modulate responses to pain (the opioid receptor systems) also are involved
in regulating negative emotions. Additionally, it could be the case that people
with greater self-control may take an attitude of active engagement to
treatment, even placebo treatment, as opposed to passively waiting to see what
happens. As a consequence they might respond more effectively. Emotional
regulation is a trainable skill. That is, psychologists can teach people
strategies to regulate how they experience and express their emotions to cope
more effectively with stress. Psychologists already teach anxiety management
strategies to people with chronic pain. It seems possible that training in
emotional regulation, such as anger management, could actually effect changes
in the opioid receptor system, resulting in a stronger placebo effect. This
might have implications for how people manage pain. Future research, such as
PET studies could determine whether training could have such an effect on the
brain and whether this assists in coping with pain.
© Scott McGreal. Please do not reproduce without
permission. Brief excerpts may be quoted as long as a link to the original
article is provided.
This article also appears on Psychology Today on
my blog Unique - Like Everybody Else.
References
Letzring, T. D., Block, J., & Funder, D. C.
(2005). Ego-control and
ego-resiliency: Generalization of self-report scales based on personality
descriptions from acquaintances, clinicians, and the self. Journal of Research in Personality, 39(4),
395-422. doi: http://dx.doi.org/10.1016/j.jrp.2004.06.003
Ode, S., & Robinson, M. D. (2007). Agreeableness and
the self-regulation of negative affect: Findings involving the
neuroticism/somatic distress relationship. Personality and Individual Differences, 43(8),
2137-2148. doi: http://dx.doi.org/10.1016/j.paid.2007.06.035
Peciña M, Azhar H, Love TM, Lu T, Fredrickson BL, Stohler CS, & Zubieta JK (2013). Personality trait predictors of placebo analgesia and neurobiological correlates. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 38 (4), 639-46 PMID: 23187726
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