Vol. 4. pp, 361 to 371 Pcrgarnon Press Lid 1979. Printed in Great Britain
0306-460379, I 101-0361$02.00/0
4 ddktite Bcll,~iors.
PERSONALITY CORRELATES OF CANNABIS DEPENDENCE* JOHN BACHMAN a n d REESE T . JONES Langley Porter Neuropsychiatric Institute University of California~ San Francisco
Abstract--The personality characteristics of 48 male volunteers were measured with the M M P I and were related to measures of cannabis withdrawal symptoms. Personality variables accounted for 25~; of the variance in these symptoms. Neurotic introversion, a tendency not to deny anxiety, absence of sensation seeking and openness were traits found to relate positively to the intensity of cannabis abstinence symptoms.
In addition to pharmacological and environmental determinants of psychoactive drug effects, individual differences in personality characteristics influence reactions to a variety of psychoactive drugs (Von Felsinger et al., 1955; Kornetsky & Humphries, 1957; Shagass, 1957; Klerman et al., 1959; Claridge & Herrington, 1960; Lindemann & Von Felsinger, 1961; Rodnight & Gooch, 1963; Nash & Stone, 1974; Claridge, 1976; Revelle et al., 1976; and Capone et al., 1976). None of these studies, however, evaluated the effect of personality on reactivity to cannabis (i.e. marijuana, hashish, THC, etc.). Several reports describe correlations between personality and levels of cannabis usage. However, the cannabis literature contains few studies of how personality differences affect the subjective experience associated with cannabis intoxication (Naditch, 1974), and very few studies which report cannabis abstinence symptoms (Jones et al., 1976). The correlational studies relating personality and cannabis usage were conducted during the last decade with students, drug treatment patients, and people in prisons and labor unions (McAree et al., 1969; Hogan et al., 1970; Zinberg & Weil, 1970; Brill et al., 1971; Harmantz et al., 1972; Knecht et al., 1972). Conceptual and methodological inadequacies limit the generalizability and validity of the findings but the results are consistent and support the hypothesis that different patterns of cannabis use are associated with different profiles on personality tests. Frequent users score higher on test scales indicative of psychopathy (i.e. impulsive, antisocial non-conformity), extraversion, sensation seeking and psychopathology. Infrequent and non-users are less antisocial and alienated but more introverted, controlled, neurotic and concerned with social achievement. These data suggest a corollary hypothesis: the personality characteristics associated with frequent cannabis use predict greater levels of cannabis withdrawal symptomatology and dependence in these people. Evidence for dependence on cannabis requires that a clear-cut and consistent withdrawal syndrome follow a period of its regular use. The syndrome may include signs and symptoms of abstinence alone and may or may not include drug-seeking behavior. Physical and psychological withdrawal symptoms occurring after abrupt cessation of prolonged cannabis intoxication have been reported in laboratory animals (Deneau & Kaymakcalan, 1971; Kaymakcalan et al., 1977) and human subjects (Williams et al., 1946; Jones et al., 1976; Nowlan & Cohen, 1977). In our laboratory (Jones et al., 1976), THC was administered orally every 4 hr in doses that were increased to 30 mg and given for 11-12 days. Tolerance developed to many of the drug's initial effects. When the THC was replaced by placebo pills under double-blind conditions, virtually every subject experienced mood changes, disturbed sleep, decreased appetite, restlessness, irritability, perspiration, chills, feverish feelings, nausea, abdominal distress, tremulousness, weight loss, loose bowel movements, hemoconcentration, sleep EEG eye movement *Research supported by funds from Contract No. HSM-42-73-181 and Grant No. DA01696 from the National Institute on Drug Abuse and Research Scientist Award No. DA00053 to Reese T. Jones, M.D., from the National Institute on Drug Abuse. 361
362
JOHN BACHMAN and REESE T. JONES
rebound, waking EEG changes and increased intraocular pressure. This withdrawal syndrome persisted for 72-96hr with most of the changes returning to pre-drug levels after 5 days. The signs and symptoms were eliminated by administration of smoked or oral doses of cannabis. Cannabis dependence was defined by the appearance of this characteristic withdrawal syndrome. This paper reports an attempt to describe the relationship between personality and variation in responses following the abrupt cessation of prolonged cannabis administration. Personality characteristics of subjects were measured by the Minnesota Multiphasic Personality Inventory (MMPI) and by Eysenck's indicators of extraversion and neuroticism. Subjects' self-reports and nurses' observations of their behavior were used to measure abstinence symptoms. METHOD
Subjects Male subjects with prior cannabis experience were recruited by advertisements in newspapers. Each subject gave his informed consent to participate in this experiment which was approved by the Committee on Human Research of the University of California, San Francisco. Subjects were paid S25.00 for each day of their participation. After thorough screening, 64 healthy and cooperative men were hospitalized and tested for 21-42 day periods. Ages ranged from 20 to 31 yr with a mean of 25 yr. Upon admission into the experiment, their mean body weight was 68.6 kg with a range of from 53.6 to 88.2 kg. Subjects had attended school for an average of 14 yr with a range of from 11 to 18 yr. They reported using marijuana regularly for an average of 5 years with a range of from 1 to 15 yr. During the 3 months prior to their participation in the experiment, they reported using marijuana "nearly every day". These men drank beer or wine on the average of "once or twice a week" and drank whiskey or hard liquor on the average of "about once a month". Many of the subjects used nicotine and caffeine daily. Men with more than infrequent and sporadic hallucinogen, stimulant, barbiturate or opiate use were not included in the experiment. One hundred thirty-three applicants completed Minnesota Multiphasic Personality Inventories (MMPIs) as part of the evaluation used to screen potential subjects. Of these 133 applicants, 64 eventually participated in the experiment. Sixty-nine applicants were excluded from participation on a variety of grounds such as physical illness, excessive polydrug use or leaving San Francisco (i.e. they were not excluded just on the basis of aberrant MMPI profiles). The mean MMPI profiles of (1) all 64 subjects, (2) a subset of 48 subjects included in some of the following analyses, and (3) the 69 excluded applicants are presented in Table 1 and Fig. 1. Forty of 64 subjects completed both M E A N M M P I PROFILES FOR ALL SUBJECTS USED IN THE EXPERIMENT (N : 64) A N D EXCLUDED APPLICANTS (N : 69)
80 -....
ALL SUBJECTSUSED EXCLUDEDAPPLICANTS
70 a
..'z~/
~, 60
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~,
50
40
I L
I F
I K
I Hs
I D
I Hy
I Pd
I Mt
I Pa
I P!
I Sc
I Ma
I Si
M M P I Scales
Fig. 1. Mean M M P I profile for all subjects in the experiment (N = 64) and excluded applicants (N = 69).
Personality correlates of cannabis dependence
+1o~
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363
+1~4
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364
JOHN BACHMAN and REESE T. JONES Table 2. Mean EPI scale scores for a subset of the subjects in this experiment (N = 40)
Extraversion Neuroticism Lie Scale
M
a
M*
a*
27.6 13.0 3.6
6,6 6.6 3.0
28.2 21.5 3.6
6.9 8.4 2.4
* Eysenck & Eysenck (1968) sample means and standard deviations for a group of 236 American college students.
forms of the Eysenck Personality Inventory (EPI; see Eysenck & Eysenck, 1968). The mean (combined) EPI "extraversion" and "neuroticism" scale scores are presented in Table 2. Interpretation of the mean M M P I profiles of these 133 men suggests that as a group they demonstrated (1) aesthetic sensitivity and passivity (i.e. the high Mf--masculine/ feminine--scores); (2) an excessive need for stimulation and excitement (i.e. the elevated M a - - h y p o m a n i a - - s c o r e s ) ; (3) alienated and non-conformist sociopathic tendencies (i.e. the elevated Pd--psychopathic deviant--scores); and (4) an ability to cope and adapt successfully (i.e. the elevated Es---ego strength--scores). The scores on the Eysenck Personality Inventory indicate these subjects were not unlike the group of normative American college students, except they possessed considerably lower neuroticism scores.
Setting The subjects lived 24 hr per day for the entire 21-42 day duration of the experiment on a 24 bed general psychiatric unit. The unit was staffed so as to both treat psychotic patients and conduct a variety of clinical research studies. Usually, 4 research subjects lived on the ward at any given time. Subjects were permitted to leave the ward or receive visitors only when supervised by research or nursing staff. Periodic blood and urine analyses were performed to screen for non-experimental drugs. There was no restriction placed on cigarette or coffee use. Subjects participated in an extensive set of biochemical and electrophysiologic tests and performed several behavioral and cognitive tasks daily, primarily between 7:00a.m. and 5:00p.m. At other times, they were free to sleep, read, play their musical instruments, etc. Of the 48 subjects from whom withdrawal symptom data were collected and analyzed, 8 were hospitalized for 21 days, 34 stayed for 30 days and 6 spent between 35 and 42 days in the hospital.
Experimental treatments During the hospitalization, subjects received single, opaque gelatin capsules that contained from zero to 30 mg of delta-9-tetrahydrocannabinol (THC) every 4 hr. The T H C was administered in the form of either pure T H C dissolved in a sesame oil vehicle or a crude cannabis extract of 29~o THC, 2.8~o cannabidiol and 1.5% cannabinol dissolved in 0.2~).4 c m - 3 of 95~o ethanol vehicle. No differences in the effects produced by these 2 preparations were observed. The doses administered to subjects were determined on the basis of the T H C content only, which was equated between the 2 preparations. These drugs were provided by the National Institute on Drug Abuse and were assayed periodically throughout the study to determine their T H C content. The capsules were given orally under double-blind conditions by a nurse. All subjects were evaluated initially during a 3-7 day baseline, pre-drug period of placebo (i.e. vehicle) administration. After an initial 10--30mg dose of THC, the dose level was increased rapidly (i.e. over 2-3 days for 24 subjects) or slowly (i.e. over 4-6 days for the remaining 24 subjects) to the maximum amount of 30 mg every 4 hr. Thirtyfive subjects received an additional 10-30mg dose at bedtime or at noon. Thus, the total daily dose administered was between 180 and 210 mg of T H C which amounted to an average of 3.1 mg/kg per day. A rough, but commonly accepted estimate of the equivalence between oral vs smoked T H C states that smoked doses are 3 times as
Personality correlates of cannabis dependence
365
"potent" as oral doses. Thus, in Mendelson et al.'s (1974) study of marijuana selfadministration, the "heavy" users smoked an average of 6 cigarettes per day. Each contained approximately 1 g of marijuana and between 18-23 mg of THC. These subjects therefore smoked about 20 mg x 6 cigarettes, or 120 mg of THC daily. But, given that about one-half of the THC present in a cigarette is lost to the smoker in side-stream smoke and between puffs, Mendelson et al.'s subjects more realistically consumed about 60mg of THC per day. This dose compares with the 180-210mg of THC consumed daily by subjects in our experiment when the smoked dose (60mg) is multiplied by 3 to convert from smoked to oral potency. The major difference between the 2 studies is the schedule of dosage administration. In our study, the THC was administered in 30mg doses given orally every 4hr around the clock. Forty-five of the 48 subjects were maintained on the fixed maximum dose for at least 8 days. Following the period of THC administration, subjects were given placebo capsules again for between 3 and 9 days and then discharged. Cessation effects
In order to study the cannabis withdrawal syndrome, the signs and symptoms following the abrupt cessation of THC administration were measured and analyzed. Cessation effects are defined operationally in two ways: (1) as the difference between the mean values of subjective and behavioral ratings made during the first 3 days immediately following cessation of THC administration and (i.e. minus) the last 3 days of maximum dose THC administration; and (2) as the difference between the mean values of subjective and behavioral ratings made during the first 3 post-THC days and (i.e. minus) the last 3 days of the pre-THC baseline. These two definitions of the cessation effect are referred to as CEF 1 and CEF 2, respectively, in what follows. The first definition emphasizes changes in a subject's state that are associated with THC withdrawal and may only reflect the disappearance of drug effects. The second definition of cessation effects, CEF 2, is included to determine if the subjective and behavioral changes associated with the end of a period of prolonged THC intoxication represent simply the disappearance of drug effects and/or the emergence of abstinence and dependence. If the drug effects were wearing off, subjects' reports of intoxication would be expected to return to basal level and no additional subjective phenomena would be expected to occur. If abstinence were evident during the post-THC period, subjects would be expected to report symptoms different from those of intoxication and at values different than the basal level. CEF 1 represents the difference in subjects' states just before and just after withdrawal of THC while CEF 2 reflects the difference in subjects' conditions before and after the entire period of THC administration. Dependent variables
Among the many measures used to evaluate the effects of THC, one set obtained daily for each subject consisted of self-reports and nurses' reports. These were recorded on the Symptom Check List (SCL-90), the Profile of Mood States (POMS) and the Nurses' Observation Scale for Inpatient Evaluation (NOSIE) (Guy, 1976). These instruments were used in this experiment because of their demonstrated sensitivity to other psychoactive drugs and because they permitted quantification and between-subject comparison. A set of SCL-90, POMS and NOSIE scales that reflect the changes following cessation of THC administration were selected on the basis of the results of repeated measures analyses of variance that showed the temporal changes before, during and after drug administration to be statistically significant. Those scales whose mean scores changed significantly from the baseline or maximum dose administration stages to the post-drug stage were considered to reflect CEF 1 and CEF 2. The scales selected to reflect the cessation effect included "hostility" and "sleep disturbance" from the SCL-90, "anger-hostility" from the POMS and "irritability" from the NOSIE. A listing of scores on the selected scales from (1) the final 3 pre-THC days, (2) the last 3 maximum dose days and (3) the first 3 post-THC placebo days was prepared
366
JOHN BACHMAN and REESE T. JONES MEAN
DALLY
COMPOSITE
FOR THE
CEF
Z SCORES
SCALES
B 7
o
.0
N
.4
5
i' U
2
-I
Z
2
.~
-3
0306-460379, I 101-0361$02.00/0
4 ddktite Bcll,~iors.
PERSONALITY CORRELATES OF CANNABIS DEPENDENCE* JOHN BACHMAN a n d REESE T . JONES Langley Porter Neuropsychiatric Institute University of California~ San Francisco
Abstract--The personality characteristics of 48 male volunteers were measured with the M M P I and were related to measures of cannabis withdrawal symptoms. Personality variables accounted for 25~; of the variance in these symptoms. Neurotic introversion, a tendency not to deny anxiety, absence of sensation seeking and openness were traits found to relate positively to the intensity of cannabis abstinence symptoms.
In addition to pharmacological and environmental determinants of psychoactive drug effects, individual differences in personality characteristics influence reactions to a variety of psychoactive drugs (Von Felsinger et al., 1955; Kornetsky & Humphries, 1957; Shagass, 1957; Klerman et al., 1959; Claridge & Herrington, 1960; Lindemann & Von Felsinger, 1961; Rodnight & Gooch, 1963; Nash & Stone, 1974; Claridge, 1976; Revelle et al., 1976; and Capone et al., 1976). None of these studies, however, evaluated the effect of personality on reactivity to cannabis (i.e. marijuana, hashish, THC, etc.). Several reports describe correlations between personality and levels of cannabis usage. However, the cannabis literature contains few studies of how personality differences affect the subjective experience associated with cannabis intoxication (Naditch, 1974), and very few studies which report cannabis abstinence symptoms (Jones et al., 1976). The correlational studies relating personality and cannabis usage were conducted during the last decade with students, drug treatment patients, and people in prisons and labor unions (McAree et al., 1969; Hogan et al., 1970; Zinberg & Weil, 1970; Brill et al., 1971; Harmantz et al., 1972; Knecht et al., 1972). Conceptual and methodological inadequacies limit the generalizability and validity of the findings but the results are consistent and support the hypothesis that different patterns of cannabis use are associated with different profiles on personality tests. Frequent users score higher on test scales indicative of psychopathy (i.e. impulsive, antisocial non-conformity), extraversion, sensation seeking and psychopathology. Infrequent and non-users are less antisocial and alienated but more introverted, controlled, neurotic and concerned with social achievement. These data suggest a corollary hypothesis: the personality characteristics associated with frequent cannabis use predict greater levels of cannabis withdrawal symptomatology and dependence in these people. Evidence for dependence on cannabis requires that a clear-cut and consistent withdrawal syndrome follow a period of its regular use. The syndrome may include signs and symptoms of abstinence alone and may or may not include drug-seeking behavior. Physical and psychological withdrawal symptoms occurring after abrupt cessation of prolonged cannabis intoxication have been reported in laboratory animals (Deneau & Kaymakcalan, 1971; Kaymakcalan et al., 1977) and human subjects (Williams et al., 1946; Jones et al., 1976; Nowlan & Cohen, 1977). In our laboratory (Jones et al., 1976), THC was administered orally every 4 hr in doses that were increased to 30 mg and given for 11-12 days. Tolerance developed to many of the drug's initial effects. When the THC was replaced by placebo pills under double-blind conditions, virtually every subject experienced mood changes, disturbed sleep, decreased appetite, restlessness, irritability, perspiration, chills, feverish feelings, nausea, abdominal distress, tremulousness, weight loss, loose bowel movements, hemoconcentration, sleep EEG eye movement *Research supported by funds from Contract No. HSM-42-73-181 and Grant No. DA01696 from the National Institute on Drug Abuse and Research Scientist Award No. DA00053 to Reese T. Jones, M.D., from the National Institute on Drug Abuse. 361
362
JOHN BACHMAN and REESE T. JONES
rebound, waking EEG changes and increased intraocular pressure. This withdrawal syndrome persisted for 72-96hr with most of the changes returning to pre-drug levels after 5 days. The signs and symptoms were eliminated by administration of smoked or oral doses of cannabis. Cannabis dependence was defined by the appearance of this characteristic withdrawal syndrome. This paper reports an attempt to describe the relationship between personality and variation in responses following the abrupt cessation of prolonged cannabis administration. Personality characteristics of subjects were measured by the Minnesota Multiphasic Personality Inventory (MMPI) and by Eysenck's indicators of extraversion and neuroticism. Subjects' self-reports and nurses' observations of their behavior were used to measure abstinence symptoms. METHOD
Subjects Male subjects with prior cannabis experience were recruited by advertisements in newspapers. Each subject gave his informed consent to participate in this experiment which was approved by the Committee on Human Research of the University of California, San Francisco. Subjects were paid S25.00 for each day of their participation. After thorough screening, 64 healthy and cooperative men were hospitalized and tested for 21-42 day periods. Ages ranged from 20 to 31 yr with a mean of 25 yr. Upon admission into the experiment, their mean body weight was 68.6 kg with a range of from 53.6 to 88.2 kg. Subjects had attended school for an average of 14 yr with a range of from 11 to 18 yr. They reported using marijuana regularly for an average of 5 years with a range of from 1 to 15 yr. During the 3 months prior to their participation in the experiment, they reported using marijuana "nearly every day". These men drank beer or wine on the average of "once or twice a week" and drank whiskey or hard liquor on the average of "about once a month". Many of the subjects used nicotine and caffeine daily. Men with more than infrequent and sporadic hallucinogen, stimulant, barbiturate or opiate use were not included in the experiment. One hundred thirty-three applicants completed Minnesota Multiphasic Personality Inventories (MMPIs) as part of the evaluation used to screen potential subjects. Of these 133 applicants, 64 eventually participated in the experiment. Sixty-nine applicants were excluded from participation on a variety of grounds such as physical illness, excessive polydrug use or leaving San Francisco (i.e. they were not excluded just on the basis of aberrant MMPI profiles). The mean MMPI profiles of (1) all 64 subjects, (2) a subset of 48 subjects included in some of the following analyses, and (3) the 69 excluded applicants are presented in Table 1 and Fig. 1. Forty of 64 subjects completed both M E A N M M P I PROFILES FOR ALL SUBJECTS USED IN THE EXPERIMENT (N : 64) A N D EXCLUDED APPLICANTS (N : 69)
80 -....
ALL SUBJECTSUSED EXCLUDEDAPPLICANTS
70 a
..'z~/
~, 60
~.__j"J
~,
50
40
I L
I F
I K
I Hs
I D
I Hy
I Pd
I Mt
I Pa
I P!
I Sc
I Ma
I Si
M M P I Scales
Fig. 1. Mean M M P I profile for all subjects in the experiment (N = 64) and excluded applicants (N = 69).
Personality correlates of cannabis dependence
+1o~
il
-FI~
363
+1~4
z
~.-+ ~ ~ +'~ ~: +'o
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364
JOHN BACHMAN and REESE T. JONES Table 2. Mean EPI scale scores for a subset of the subjects in this experiment (N = 40)
Extraversion Neuroticism Lie Scale
M
a
M*
a*
27.6 13.0 3.6
6,6 6.6 3.0
28.2 21.5 3.6
6.9 8.4 2.4
* Eysenck & Eysenck (1968) sample means and standard deviations for a group of 236 American college students.
forms of the Eysenck Personality Inventory (EPI; see Eysenck & Eysenck, 1968). The mean (combined) EPI "extraversion" and "neuroticism" scale scores are presented in Table 2. Interpretation of the mean M M P I profiles of these 133 men suggests that as a group they demonstrated (1) aesthetic sensitivity and passivity (i.e. the high Mf--masculine/ feminine--scores); (2) an excessive need for stimulation and excitement (i.e. the elevated M a - - h y p o m a n i a - - s c o r e s ) ; (3) alienated and non-conformist sociopathic tendencies (i.e. the elevated Pd--psychopathic deviant--scores); and (4) an ability to cope and adapt successfully (i.e. the elevated Es---ego strength--scores). The scores on the Eysenck Personality Inventory indicate these subjects were not unlike the group of normative American college students, except they possessed considerably lower neuroticism scores.
Setting The subjects lived 24 hr per day for the entire 21-42 day duration of the experiment on a 24 bed general psychiatric unit. The unit was staffed so as to both treat psychotic patients and conduct a variety of clinical research studies. Usually, 4 research subjects lived on the ward at any given time. Subjects were permitted to leave the ward or receive visitors only when supervised by research or nursing staff. Periodic blood and urine analyses were performed to screen for non-experimental drugs. There was no restriction placed on cigarette or coffee use. Subjects participated in an extensive set of biochemical and electrophysiologic tests and performed several behavioral and cognitive tasks daily, primarily between 7:00a.m. and 5:00p.m. At other times, they were free to sleep, read, play their musical instruments, etc. Of the 48 subjects from whom withdrawal symptom data were collected and analyzed, 8 were hospitalized for 21 days, 34 stayed for 30 days and 6 spent between 35 and 42 days in the hospital.
Experimental treatments During the hospitalization, subjects received single, opaque gelatin capsules that contained from zero to 30 mg of delta-9-tetrahydrocannabinol (THC) every 4 hr. The T H C was administered in the form of either pure T H C dissolved in a sesame oil vehicle or a crude cannabis extract of 29~o THC, 2.8~o cannabidiol and 1.5% cannabinol dissolved in 0.2~).4 c m - 3 of 95~o ethanol vehicle. No differences in the effects produced by these 2 preparations were observed. The doses administered to subjects were determined on the basis of the T H C content only, which was equated between the 2 preparations. These drugs were provided by the National Institute on Drug Abuse and were assayed periodically throughout the study to determine their T H C content. The capsules were given orally under double-blind conditions by a nurse. All subjects were evaluated initially during a 3-7 day baseline, pre-drug period of placebo (i.e. vehicle) administration. After an initial 10--30mg dose of THC, the dose level was increased rapidly (i.e. over 2-3 days for 24 subjects) or slowly (i.e. over 4-6 days for the remaining 24 subjects) to the maximum amount of 30 mg every 4 hr. Thirtyfive subjects received an additional 10-30mg dose at bedtime or at noon. Thus, the total daily dose administered was between 180 and 210 mg of T H C which amounted to an average of 3.1 mg/kg per day. A rough, but commonly accepted estimate of the equivalence between oral vs smoked T H C states that smoked doses are 3 times as
Personality correlates of cannabis dependence
365
"potent" as oral doses. Thus, in Mendelson et al.'s (1974) study of marijuana selfadministration, the "heavy" users smoked an average of 6 cigarettes per day. Each contained approximately 1 g of marijuana and between 18-23 mg of THC. These subjects therefore smoked about 20 mg x 6 cigarettes, or 120 mg of THC daily. But, given that about one-half of the THC present in a cigarette is lost to the smoker in side-stream smoke and between puffs, Mendelson et al.'s subjects more realistically consumed about 60mg of THC per day. This dose compares with the 180-210mg of THC consumed daily by subjects in our experiment when the smoked dose (60mg) is multiplied by 3 to convert from smoked to oral potency. The major difference between the 2 studies is the schedule of dosage administration. In our study, the THC was administered in 30mg doses given orally every 4hr around the clock. Forty-five of the 48 subjects were maintained on the fixed maximum dose for at least 8 days. Following the period of THC administration, subjects were given placebo capsules again for between 3 and 9 days and then discharged. Cessation effects
In order to study the cannabis withdrawal syndrome, the signs and symptoms following the abrupt cessation of THC administration were measured and analyzed. Cessation effects are defined operationally in two ways: (1) as the difference between the mean values of subjective and behavioral ratings made during the first 3 days immediately following cessation of THC administration and (i.e. minus) the last 3 days of maximum dose THC administration; and (2) as the difference between the mean values of subjective and behavioral ratings made during the first 3 post-THC days and (i.e. minus) the last 3 days of the pre-THC baseline. These two definitions of the cessation effect are referred to as CEF 1 and CEF 2, respectively, in what follows. The first definition emphasizes changes in a subject's state that are associated with THC withdrawal and may only reflect the disappearance of drug effects. The second definition of cessation effects, CEF 2, is included to determine if the subjective and behavioral changes associated with the end of a period of prolonged THC intoxication represent simply the disappearance of drug effects and/or the emergence of abstinence and dependence. If the drug effects were wearing off, subjects' reports of intoxication would be expected to return to basal level and no additional subjective phenomena would be expected to occur. If abstinence were evident during the post-THC period, subjects would be expected to report symptoms different from those of intoxication and at values different than the basal level. CEF 1 represents the difference in subjects' states just before and just after withdrawal of THC while CEF 2 reflects the difference in subjects' conditions before and after the entire period of THC administration. Dependent variables
Among the many measures used to evaluate the effects of THC, one set obtained daily for each subject consisted of self-reports and nurses' reports. These were recorded on the Symptom Check List (SCL-90), the Profile of Mood States (POMS) and the Nurses' Observation Scale for Inpatient Evaluation (NOSIE) (Guy, 1976). These instruments were used in this experiment because of their demonstrated sensitivity to other psychoactive drugs and because they permitted quantification and between-subject comparison. A set of SCL-90, POMS and NOSIE scales that reflect the changes following cessation of THC administration were selected on the basis of the results of repeated measures analyses of variance that showed the temporal changes before, during and after drug administration to be statistically significant. Those scales whose mean scores changed significantly from the baseline or maximum dose administration stages to the post-drug stage were considered to reflect CEF 1 and CEF 2. The scales selected to reflect the cessation effect included "hostility" and "sleep disturbance" from the SCL-90, "anger-hostility" from the POMS and "irritability" from the NOSIE. A listing of scores on the selected scales from (1) the final 3 pre-THC days, (2) the last 3 maximum dose days and (3) the first 3 post-THC placebo days was prepared
366
JOHN BACHMAN and REESE T. JONES MEAN
DALLY
COMPOSITE
FOR THE
CEF
Z SCORES
SCALES
B 7
o
.0
N
.4
5
i' U
2
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Z
2
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