Substance Use Disorders 415skills (Ramaekers et al., 2006). THC ultimately activates the dopamine reward sys-
tem (NIDA, 2000).
Like the effects of LSD, marijuana’s effects depend on the user’s mood, expecta-tions, and environment. For example, one study found that participants who were
given THC and knew that they were receiving THC liked the effects and wanted
more than did participants who were told they were receiving an antinausea drug
but actually received THC (Kirk, Doty, & de Wit, 1998).
A user of marijuana who develops abuse or dependence will experience with-drawal symptoms after he or she stops using marijuana; such symptoms include
irritability, anxiety, depression, decreased appetite, and disturbed sleep (Budney
et al., 2004; Kouri & Pope, 2000). Studies have found that chronic marijuana use
adversely affects learning, memory, and motivation—even when the user has not
taken the drug recently and is not under its direct infl uence (Lane et al., 2005;
Pope et al., 2001; Pope & Yurgelin-Todd, 1996). Smoking marijuana is also asso-
ciated with an increased risk of heart attack (Mittleman et al., 2001). One survey
found that of the approximately 7 million Americans who abuse or are dependent
on an illegal substance, over half of them abuse or are dependent on marijuana
(SAMHSA, 2004).
Dissociative Anesthetics
Adissociative anesthetic produces a sense of detachment from the user’s surroundings—
adissociation. The word anesthetic in the name refl ects the fact that many of these
drugs were originally developed as anesthetics to be used during surgery. Disso-
ciative anesthetics act like depressants and also affect gluamate activity (Kapur &
Seeman, 2002). These drugs can distort visual and auditory perception. Drugs of
this type have been referred to as “club drugs” because they tend to be taken before
or during an evening of dancing at a nightclub. The most commonly abused mem-
bers of this class of drugs are phencyclidine and ketamine, which we discuss in the
following sections.
Phencyclidine (PCP)
Phencyclidine (PCP, also known as “angel dust” and “rocket fuel”) became a street
drug in the 1960s. It can be snorted, ingested, or smoked, and users can quickly be-
gin to take it compulsively. PCP abusers may report feeling powerful and invulner-
able while the drug is in their system, and they may become violent or suicidal, at
which point they may end up in an emergency room (NIDA, 2007f). Possible medi-
cal effects of high doses include a decrease in breathing and heart rates, dizziness,
nausea and vomiting, seizures, coma, and death; coma and death are more likely
if PCP is used along with one or more other drugs. With abuse can come memory,
speech, and cognitive problems, even up to a year after the last use (NIDA, 2007f).
PCP has deleterious effects even when taken at low to moderate doses. Medicaleffects include increased blood pressure, heart rate, and sweating, coordination prob-
lems, and numbness in the hands and feet. At higher doses, PCP users may experience
symptoms of hallucinations, delusions, paranoia, disordered thinking, and other
symptoms of schizophrenia (see Chapter 12), which may bring them to the attention
of mental health professionals, as occurred for the man in Case 9.6. Repeated PCP
use can lead to craving for, and compulsive use of, the drug (NIDA, 2008d).
CASE 9.6 • FROM THE OUTSIDE: PCP Abuse
The patient is a 20-year-old man who was brought to the hospital, trussed in ropes, by his four
brothers. This is his seventh hospitalization in the last 2 years, each for similar behavior. One
of his brothers reports that he “came home crazy,” threw a chair through a window, tore a gas
heater off the wall, and ran into the street. The family called the police, who apprehended him
shortly thereafter as he stood, naked, directing traffi c at a busy intersection. He assaulted the
arresting offi cers, escaped from them, and ran home screaming threats at his family. There his
brothers were able to subdue him.
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