The Effects of Cannabis Use in People With Schizophrenia on Clinical, Neuropsychological and Physiological Phenotypes
| Status: | Terminated |
|---|---|
| Conditions: | Schizophrenia |
| Therapuetic Areas: | Psychiatry / Psychology |
| Healthy: | No |
| Age Range: | 18 - 50 |
| Updated: | 4/21/2016 |
| Start Date: | June 2005 |
| End Date: | May 2011 |
Approximately 25% of people with schizophrenia abuse marijuana. These people may be using
marijuana to self-medicate symptoms such as hallucinations (hearing or seeing things that
are not heard or seen by others) or delusions (false beliefs i.e. people are harassing or
persecuting them) or the depressed and anxious feelings brought on by these symptoms.
Currently, it is unknown whether marijuana makes schizophrenia better or worse. Marijuana
intoxication in people without schizophrenia generally causes decreased recall of words, may
decrease reaction time and decrease inhibition. Additionally, marijuana may cause
distractibility as demonstrated by difficulty keeping their eyes on a moving target and
difficulty inhibiting their response to repetitive tones. However, marijuana may have
different effects in schizophrenia. Receptors for cannabis (marijuana) are concentrated in
the brain and maladjustment of the cannabinoid system may be associated with the difficulty
in thinking found in schizophrenia. The proposed research project examines if clinical
symptoms, learning, memory, inhibition and distractibility are improved or made worse by the
acute ingestion of tetrahydrocannabinol (THC).
marijuana to self-medicate symptoms such as hallucinations (hearing or seeing things that
are not heard or seen by others) or delusions (false beliefs i.e. people are harassing or
persecuting them) or the depressed and anxious feelings brought on by these symptoms.
Currently, it is unknown whether marijuana makes schizophrenia better or worse. Marijuana
intoxication in people without schizophrenia generally causes decreased recall of words, may
decrease reaction time and decrease inhibition. Additionally, marijuana may cause
distractibility as demonstrated by difficulty keeping their eyes on a moving target and
difficulty inhibiting their response to repetitive tones. However, marijuana may have
different effects in schizophrenia. Receptors for cannabis (marijuana) are concentrated in
the brain and maladjustment of the cannabinoid system may be associated with the difficulty
in thinking found in schizophrenia. The proposed research project examines if clinical
symptoms, learning, memory, inhibition and distractibility are improved or made worse by the
acute ingestion of tetrahydrocannabinol (THC).
The trial will be a double two period (visit) blind cross-over trial with one arm dronabinol
10 mg one arm a placebo control. The order of doses and placebo will be randomized with the
restriction that half of the subjects will receive each order. This counterbalances possible
visit effects or learning effects associated with the visits. The use of an oral cannabis
analog is not equivalent to smoking as the onset of action is slower. This is why people who
use dronabinol for chronic pain prefer to smoke cannabis. There is no "high" associated with
dronabinol. However, the active ingredients are the same, THC, which will have similar
effects on the cannabinoid 1 receptor. Ethically, we did not feel we could ask people to
smoke cannabis on one day of study. Subjects will present to the GCRC at 5:00 p.m. They will
abstain from use of cannabis overnight. The following morning, at 8:00 a.m., the subject
will provide a urine sample for a toxicology screen and a blood sample for quantitative THC
levels. They will then be administered either 10 mg of dronabinol or an identical placebo on
an alternate day. The subject will then have a baseline assessment of clinical positive and
negative symptoms measured by the Brief Psychiatric Rating Scale (BPRS). The majority
(70-90%) of people with schizophrenia smoke cigarettes. Thus, it is likely that in this
population that smokes cannabis, 100% will also be cigarette smokers. The effects of
nicotine via cigarette smoking on the endophenotypes studied is an acute effect, with a peak
at about 5 minutes. To preclude nicotine effects on endophenotypes, we have the patient not
smoke for 20 minutes prior to and during testing. Nicotine is quickly removed from the body
when inhaled and its effects wear off within 20 minutes. Two hours after administration, the
subject will perform the following tests: P50 auditory evoked potential- the recording will
consist of the presentation of 5 sets of 16 click pairs with an intrapair interval of 500 ms
heard through headphones with a 3-minute rest between sets. Brain wave responses will be
recorded; neurocognitive assessment-the California Verbal Learning Test will measure verbal
memory and the Stroop will measure inhibition; clinical symptom assessment- The BPRS will
again be administered measure positive and negative symptoms; and a blood sample will be
collected for quantitative THC levels. They will then be escorted by a Clinical Research
Center nurse over to a laboratory at Colorado Psychiatric Hospital to perform smooth pursuit
eye movements In performing smooth pursuit eye movements, they will watch a dot moving
across a computer screen while infrared sensors that are placed just in front of their eyes
record their eye movements. Each subject performs 3 trials of one minute each, with 2
minutes rest between each recording. Subjects will be reassessed by the BPRS for drug
exacerbation of symptoms, will have vitals, will be checked for adverse effects, will
perform a sobriety test (the standard test used in roadside testing i.e. walking a straight
line and finger to nose testing) which will be assessed by Dr. Olincy, who is experienced in
assessing sobriety, to assure that the patient is not acutely intoxicated and able to
perform normal functions that require coordination. If they fail the sobriety test, they
will be asked to remain in the (General Clinical Research Center (GCRC) until they can pass
the sobriety test. Otherwise, they will then will be discharged at 5:00 p.m. Transportation
to and from the GCRC will be by a provided cab service. Subjects will be randomized in
blocks of 4 or 6 to the order in which they receive placebo or dronabinol. The interval
between the two days of testing will be 1 week.
10 mg one arm a placebo control. The order of doses and placebo will be randomized with the
restriction that half of the subjects will receive each order. This counterbalances possible
visit effects or learning effects associated with the visits. The use of an oral cannabis
analog is not equivalent to smoking as the onset of action is slower. This is why people who
use dronabinol for chronic pain prefer to smoke cannabis. There is no "high" associated with
dronabinol. However, the active ingredients are the same, THC, which will have similar
effects on the cannabinoid 1 receptor. Ethically, we did not feel we could ask people to
smoke cannabis on one day of study. Subjects will present to the GCRC at 5:00 p.m. They will
abstain from use of cannabis overnight. The following morning, at 8:00 a.m., the subject
will provide a urine sample for a toxicology screen and a blood sample for quantitative THC
levels. They will then be administered either 10 mg of dronabinol or an identical placebo on
an alternate day. The subject will then have a baseline assessment of clinical positive and
negative symptoms measured by the Brief Psychiatric Rating Scale (BPRS). The majority
(70-90%) of people with schizophrenia smoke cigarettes. Thus, it is likely that in this
population that smokes cannabis, 100% will also be cigarette smokers. The effects of
nicotine via cigarette smoking on the endophenotypes studied is an acute effect, with a peak
at about 5 minutes. To preclude nicotine effects on endophenotypes, we have the patient not
smoke for 20 minutes prior to and during testing. Nicotine is quickly removed from the body
when inhaled and its effects wear off within 20 minutes. Two hours after administration, the
subject will perform the following tests: P50 auditory evoked potential- the recording will
consist of the presentation of 5 sets of 16 click pairs with an intrapair interval of 500 ms
heard through headphones with a 3-minute rest between sets. Brain wave responses will be
recorded; neurocognitive assessment-the California Verbal Learning Test will measure verbal
memory and the Stroop will measure inhibition; clinical symptom assessment- The BPRS will
again be administered measure positive and negative symptoms; and a blood sample will be
collected for quantitative THC levels. They will then be escorted by a Clinical Research
Center nurse over to a laboratory at Colorado Psychiatric Hospital to perform smooth pursuit
eye movements In performing smooth pursuit eye movements, they will watch a dot moving
across a computer screen while infrared sensors that are placed just in front of their eyes
record their eye movements. Each subject performs 3 trials of one minute each, with 2
minutes rest between each recording. Subjects will be reassessed by the BPRS for drug
exacerbation of symptoms, will have vitals, will be checked for adverse effects, will
perform a sobriety test (the standard test used in roadside testing i.e. walking a straight
line and finger to nose testing) which will be assessed by Dr. Olincy, who is experienced in
assessing sobriety, to assure that the patient is not acutely intoxicated and able to
perform normal functions that require coordination. If they fail the sobriety test, they
will be asked to remain in the (General Clinical Research Center (GCRC) until they can pass
the sobriety test. Otherwise, they will then will be discharged at 5:00 p.m. Transportation
to and from the GCRC will be by a provided cab service. Subjects will be randomized in
blocks of 4 or 6 to the order in which they receive placebo or dronabinol. The interval
between the two days of testing will be 1 week.
Inclusion Criteria:
- Male and females
- 18 and 50 years of age
- Diagnosis of schizophrenia
- Chronic cannabis users who have used for at least 1 year
- Using cannabis at least once weekly
- Currently being treated with antipsychotic medication
- Must be on a the same dose of antipsychotic medication for at least 3 months.
- Females of childbearing potential must use an adequate form of birth control while
participating.
- Participants will be required to have blood pressures greater than 90/60 and less
than 140/90.
Exclusion Criteria:
- Use of illicit drugs other than cannabis
- Any psychiatric hospitalizations within 3 months
- pregnancy in females
- taking clozapine
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