Cannabis Flashcards
What plant is Cannabis derived from?
Hemp - Cannabis Sativa. Also used for rope, cloth and paper and the seeds are used for birdfeed.
What is the psychoactive agent in cannabis?
Delta9 Tetrahydocannabinol (THC)
Where is THC concentrated?
In the sticky resin secreted by the flowing tops of female plants.
In what three main forms is cannabis obtainable?
- Marijuana (dried and crumbled leaves, smoked)
- Hashish (solid, prepared from resin, different concentrations)
- Hash oil (reduced alcoholic extract, single drop placed in joint)
Why does the THC content in cannabis vary?
Due to sinsemilla - if pollination is prevented it increases potency.
In what ways was cannabis first used?
2700 BC - Medical use in China
2000 BC - Religious use in India
1000 AD - Hashish use in Arab world
When were the Marijuana Tax Act and the first laws legalising medical use?
1937 and 1996, respectively.
How was cannabis use introduced into the west?
From Egypt by Napoleon’s soldiers.
Name two notable ‘hashish eaters’ found by Mareau.
Victor Hugo and Alexandre Dumas.
Approximately how much cannabis does a typical joint contain?
0.5-1g
if THC content 4% = 40mg THC/joint
How is THC absorbed and what percentage of it is absorbed, when smoking a joint?
Burning marajuana = vaporisation = absorption = blood plasma
20% of THC absorbed, can be increased by breath holding (Black et al, 1998 7 vs. 15s hold)
After peak levels of THC in the blood are reached, how do they fall?
Through metabolism in liver and fat storage.
What is the half-life of THC, and how long can it be detected in urine for?
20-30 hours and 2-3 weeks respectively.
What did Devane et al (1988) do?
Identified the cannabinoid receptor (CB1), agonised by THC.
Where are cannabis receptors active?
In areas consistent with behavioural effects, e.g. the hippocampus for spatial memory (also substantia nigra and globus padillus)
What is the antagonist for CB1 receptors?
SR 141716
According to Iversen (2000), what are the acute behavioural effects of cannabis?
- The ‘buzz’ (brief) - light-headedness, dizziness, tingling in extremities due to increased blood flow and HR.
- The ‘high’ - euphoria, exilharation, disinhibition (the giggles)
- Being stoned (large amount) - calm, relaxed, dream-like state.
What psychological changes are involved in being ‘stoned’?
- A calm, relaxed, dream-like state.
- Sensations of floating, enhanced visual and auditory perception
- Slowing of the perception of time
- Changes in sociability (increases or decreases)
What are the physiological effects of cannabis?
- Increased blood flow to skin = warmth
- Increased HR = pounding pulse sensation
- The ‘munchies’.
Who has demonstrated the munchies, and what mechanisms is it caused by?
- In humans: Foltin et al (1988), in rats: Williams et al (1998)
- Caused by increase in palatability (Williams and Kirkham, 2002, rats) and hyperphagia (abolished by CB1 antagonist, Williams & Kirkham, 2002)
What did Heustis et al (2001) find when studying how the effects of marijuana are attenuated by a CB1 antagonist?
Had antagonist and placebo group, both given a joint.
In antagonist group, feeling high and stoned was reduced (self-report q.aire), as was HR, but effects weren’t abolished.
What do Heustis et al (2001)’s findings suggest?
Either a stronger dose of CB1 antagonist was necessary, or another mechanism mediates effects.
What did Agurell et al (1986) find?
That route of administration has a substantial effect on blood plasma levels of THC after smoking a joint or oral consumption. (Oral slower to peak but lasted longer).
Why do smokers not report a peak until after the joint has been finished?
- Brain and plasma concentrations are not yet at equilibrium
- THC isn’t fully metabolised.
What did Curran et al (2002) find about the effects of oral THC consumption on verbal memory?
That recall scores decreased with more THC, especially over time.
However according to Hart et al (2001) the effect is attenuated in long term users - cognitive tolerance.
What effect does cannabis have on driving?
Low doses have relatively few effects.
Moderate or high doses could lead to impaired performance in demanding tasks.
According to Ramaekers et al (2004), it’s a risk factor in car accidents.
What have animal studies on SR 141716 found?
Richardson et al (1998) - induces hyperalgesia
Black (2004) - decreases food consumption.
What have animal studies on the effect of CB1 knockouts (mutant mice) found?
- Varvel and Lichtman (2002) normal acquisition of spatial learning (hidden platforms, then moved), impaired reversal learning.
- Marsicano et al (2002) normal fear conditioning (Skinner box tone+shock) but impaired extinction.
= deficit in unlearning?
What did Varvel and Lichtman (2002) show in lever-pressing rats?
Rats trained to press lever for cocaine, then extenguished and IV THC introduced, increased lever pressing again.
Effect abolished with CB1 antagonist.
What did Valjent and Maldonado (2000) find about THC in mice?
Conditioned place preference (drug-seeking metaphor) if pre-exposed in home cages.
Experience first aversive then rewarding.
At what age are people most likely to initiate marijuana use, according to Brooks et al (1999)?
Around 13-22, peaks at 17.
About what percentage of people use cannabis in the UK and US?
4.6%.
According to Gruber and Pope (2002), what are the risk factors for progression from an initial to a regular user?
- Family disturbances
- Drug use by family/peers
- School performance
- Age of onset
According to human studies, does tolerance develop with repeated cannabis use?
- Compton et al (1990) = yes
- Kirk & de Wit (1999), Lindgren et al (1981) = no, same high in frequent/infrequent users.
What does the slippery slope argument assume about cannabis?
That it’s a gateway (natural course) to harder drugs. However this is difficult to assess.
According to animal studies, does tolerance develop with repeated cannabis use?
- Breivogel et al (1999) (rats), after daily THC injection for 3 weeks showed progressive reduction in CB1 density and agonist activity, with some brain areas totally desensitised = physiological support.
What three things are involved in cannabis dependence?
- Difficulty stopping
- Craving
- Withdrawal symptoms
What do studies report that cannabis abstinence triggers?
Irritability, anxiety, depression, sleep disturbances, aggression, decreased appetite.
Resembles nicotine withdrawal symptoms.
How long do cannabis withdrawal symptoms last?
Worst in first 2 weeks, can last over a month.
What withdrawal effects did early animal studies find?
None, but THC has a long half life so is still present in system.
What do precipitated withdrawal studies (e.g. Aceto et al (1996)) do?
Rats given regular THC injections, then SR 141716.
Display symptoms of hyperactivity (shaking, face rubbing, scratching)
What might the findings of precipitated withdrawal studies be due to?
Rats being stressed - de Fonseca (1997) found they had high levels of CRH.
How is CBT used to treat cannabis dependence?
Pts are rewarded with vouchers for providing cannabis-free urine samples.
Is CBT for cannabis dependence effective?
A little, but significant relapse rate (Moore and Budney, 2003)
What did Haney et al (2004) suggest about easing cannabis withdrawal symptoms?
Oral consumption of THC.
What are the long term psychological effects of chronic cannabis use?
- Decreased education performance
- Cognitive deficits
What has research found about the link between chronic cannabis use and school performance?
- Lynsky and Hall (2000) = more negative attitude, poorer grades, absenteeism, linked to amotivational syndrome (apathy, aimlessness, lack of productivity, long term planning and motivation)
- Fergusson et al (2003) cannabis use predicts poor school performance and drop-out rates.
What has research found about the link between chronic cannabis use and cognitive deficits?
- Solowij et al (2002) - deficient 1 and 7 days after exposure in learning, memory and attention.
- Pope et al (2001) - no difference between heavy users and controls after 28 days = reversible.
What are the health effects of chronic cannabis use?
- Not death
- High levels of tar and carbon monoxide (carcinogens) = cancer
- Immune system
- Reproductive function
What has research found on the effects of chronic cannabis use on the immune system?
Cabreal & Pettit (1998) - THC suppresses immune function, increased risk of viral and bacterial infection.
What has research found on the effects of chronic cannabis use on reproductive function?
In women - suppresses luteinising hormone release (but can be tolerated)
In men - Smith & Asch (1987) = decreased sperm count, but only in heavy users.
What are the clinical applications of cannabis?
- Synthetic compounds (dronabinol=antiemetic for chemo patients, nabilone=appetite stimulant for AIDS patients).
- Chronic pain treatment (MS, spinal cord injury, glaucoma)
- Limited widespread use due to side effects and that it’s more effective when smoked.
What is HU-221?
A cannabinoid that doesn’t activate CB1 receptors and therefore has no side effects - undergoing clinical trials.
