Laboratory studies have shown that animals exhibit symptoms of drug
withdrawal after cessation of prolonged marijuana administration. Some
human studies have also demonstrated withdrawal symptoms such as
irritability, stomach pain, aggression, and anxiety after cessation of
oral administration of tetrahydrocannabinol (THC), marijuana's principal
psychoactive component. Now, NIDA-supported researchers at McLean Hospital
in Belmont, Massachusetts, and Columbia University in New York City have
shown that individuals who regularly smoke marijuana experience withdrawal
symptoms after they stop smoking the drug.
"These studies suggest that in real-world situations abstinence from
daily marijuana smoking creates withdrawal symptoms similar to those of
other drugs of abuse," says Dr. Jag Khalsa of NIDA's Center on AIDS and
Other Medical Consequences of Drug Abuse. "Marijuana smokers may continue
to use the drug to prevent the irritability and discomfort they experience
when they stop."
Dr. Elena Kouri and her colleagues at the Biological Psychiatry
Laboratory at McLean Hospital found that long-term heavy marijuana users
became more aggressive during abstinence from marijuana than did former or
infrequent users. Previous studies of withdrawal symptoms have relied
largely on patients' subjective reports of a range of symptoms, Dr. Kouri
notes. "We studied measurable changes in one specific symptom-aggression,"
The researchers recruited two groups of male and female volunteers: 17
current long-term users of marijuana and a control group of 20 infrequent
or former users. Current long-term users were smoking marijuana daily at
the time of recruitment and had smoked marijuana at least 5,000 times-the
equivalent of smoking once each day for more than 13 years. The infrequent
or former users had not smoked more than 50 times in their life and had
smoked less than once per month in the past year, or had formerly smoked
at least daily but had not smoked more than once per week for the past 3
"The results demonstrate that abstinence is associated with
unpleasant behavioral symptoms that may contribute to continued drug
At the beginning of the study, all participants were instructed to
refrain from any marijuana use for 28 days. Abstinence was monitored by
analysis of daily observed urine sampling. Cigarette smokers were allowed
to continue their usual tobacco use.
the first weeks of abstinence, long-term current marijuana smokers
made more aggressive responses on a computerized game than did
infrequent or former smokers. The graph shows the average number
of aggressive responses in 17 long-term daily (Solid Square)
and 20 infrequent or former (Open Square) marijuana smokers.
(Star = significantly different from former smokers.)
Aggression was measured on the first day of the study and after 1, 3,
7, and 28 days of abstinence. To measure aggression, the researchers used
a 20-minute computerized test that participants were told would measure
motor skills and other physiological characteristics. Participants were
told that pressing one button in a certain pattern would add points to
their score and that pressing another button would subtract points from
the score of their opponent, who could similarly add or subtract
In fact, Dr. Kouri says, there was no human opponent; the computer was
programed to subtract points randomly in order to give the illusion of a
human opponent. At the end of each session, aggressive responses-those
that subtracted from the supposed opponent's points-were compared with
nonagressive responses-those that added to the participant's points. Dr.
Kouri notes that studies involving parolees with a history of violent
behavior have shown a close correlation between performance on this game
and actual aggression.
After 1, 3, and 7 days of abstinence, current marijuana users
registered significantly more aggressive responses-more than twice as many
on days 3 and 7-than the control group. By the 28th day, there was no
significant difference between groups. Aggressive behavior was limited to
responses in the test situation, Dr. Kouri notes; participants did not
display overt hostility. "At this point we do not know exactly how these
findings reflect changes in aggressive behavior outside the laboratory,"
Dr. Kouri says. "But the results demonstrate that abstinence is associated
with unpleasant behavioral symptoms that may contribute to continued drug
Other Withdrawal Symptoms
Studies at Columbia University in New York City have demonstrated that,
in addition to aggression, marijuana smokers experience other withdrawal
symptoms such as anxiety, stomach pain, and increased irritability during
abstinence from the drug. "These results suggest that dependence may be an
important consequence of repeated daily exposure to marijuana," says
NIDA-supported researcher Dr. Margaret Haney.
Dr. Haney and her colleagues investigated the effects of abstinence on
12 adult males with an average age of 28 years who, in the laboratory,
smoked marijuana with THC concentrations of 3.1 percent or 1.8 percent, or
marijuana cigarettes containing no active THC. All participants smoked
inactive marijuana during the first 4 days of the study followed by either
the high concentration, low concentration, or inactive marijuana on
alternating 4-day periods. Three times each day, the participants
completed a 50-item checklist that rated physical conditions such as
hunger, dizziness, and headache and aspects of their mood, for example,
anxiety, talkativeness, friendliness, or depression.
"The withdrawal symptoms are not as dramatic as those associated
with withdrawal from opiates or alcohol, but are still
Abstinence from either high- or low-concentration marijuana resulted in
reduced hunger, decreased ratings of "friendly" and "content," and
increased ratings of "irritability," "stomach pain," and "anxiety."
Moreover, Dr. Haney notes, participants receiving high-concentration
marijuana rated the drug's effects higher ("good drug effect,"
"stimulated," "high") on the first day of exposure than on the fourth day,
indicating the development of tolerance to THC.
"It appears likely that the onset of the withdrawal symptoms we
observed in this study may contribute to maintaining chronic marijuana
use," Dr. Haney says. "The withdrawal symptoms are not as dramatic as
those associated with withdrawal from opiates or alcohol, but are still
significant to the individual marijuana user. These symptoms must be taken
into account in order to develop effective treatment programs for
Kouri, E.M.; Pope, H.G.; and Lukas, S.E. Changes in aggressive behavior
during withdrawal from long-term marijuana use. Psychopharmacology,
Haney, M.; Ward, A.S.; Comer, S.D.; Foltin, R.W.; and Fischman, M.W.
Abstinence symptoms following smoked marijuana in humans.