the health of one’s body. The interaction of these drugs with the
reward-reinforcement neural pathways in the brain is believed to
be an important component of the neurobiology of addiction (see
Chapter 21).Psychedelics. This is perhaps the most interesting group of all known
psychoactive substances. Psychedelics produce a variety of complex
effects on the brain and mind, including intensified thoughts and
feelings and altered sensory perception. Reported effects range from
novel and insightful thoughts and feelings, to experiences of awe and
profound connection with nature, to anxiety and panic.
To a greater degree than is the case for other psychoactive drugs,
the effects of psychedelics on behavior and mental experience are
influenced by what is termed “set and setting.” Set (or mental set)
refers to psychological factors such as expectations, memories of
prior experiences, mood, and so on. Setting refers to the physical en-
vironment in which the experience of intoxication takes place—for
example, alone, in a social setting with others, therapeutic context
with a healer, inside a room, or outside in nature. The effects of any
psychoactive drug will be affected by set and setting, but some drugs
are more susceptible to set-and-setting effects than others. Thus,
caffeine may generally have a small set-and-setting effect, and alcohol
an intermediate one, while for the psychedelics the set-and-setting
effect is generally very large.
As their properties came under investigation by twentieth-century
biomedical science, many of these compounds were initially called
psychotomimetics, because it was believed their effects were much
like the symptoms of psychosis. This term was eventually eclipsed
in favor of hallucinogen, highlighting that effects may include alter-