examine individual characteristics, characteristics of the treatment and characteristics
of the health professional, or interactive theories in that they involve an examination of
the processes involved in the interactions between patients, the treatment and the health
professionals.Non-interactive theories
Characteristics of the individual
Individual trait theories suggest that certain individuals have characteristics that
make them susceptible to placebo effects. Such characteristics have been described as
emotional dependency, extraversion, neurosis and being highly suggestible. Research has
also suggested that individuals who respond to placebos are introverted. However, many
of the characteristics described are conflicting and there is little evidence to support
consistent traits as predictive of placebo responsiveness.Characteristics of the treatment
Other researchers have focused on treatment characteristics and have suggested that
the characteristics of the actual process involved in the placebo treatment relates to the
effectiveness or degree of the placebo effect. For example, if a treatment is perceived by
the individual as being serious, the placebo effect will be greater. Accordingly, surgery,
which is likely to be perceived as very serious, has the greatest placebo effect, followed by
an injection, followed by having two pills versus one pill. Research has also looked at the
size of the pill and suggests that larger pills are more effective than small pills in eliciting
a change.Characteristics of the health professional
Research has also looked at the characteristics of the health professional suggesting that
the kind of professional administering the placebo treatment may determine the degree
of the placebo effect. For example, higher professional status and higher concern have
been shown to increase the placebo effect.Problems with the non-interactive theories
Theories that examine only the patient, only the treatment or only the professional
ignore the interaction between patient and health professional that occurs when a
placebo effect has taken place. They assume that these factors exist in isolation and
can be examined independently of each other. However, if we are to understand
placebo effects then perhaps theories of the interaction between health professionals and
patients described within the literature (see Chapter 4) can be applied to understanding
placebos.PLACEBOS AND THE INTERRELATIONSHIP BETWEEN BELIEFS, BEHAVIOUR AND HEALTH 311