NSCI 302: marijuana

3 species of hemp plant

cannabis sativa, cannabis indica, cannabis ruderalis

cannabinoids

found in sticky resin covering the leaves and flowers of the plant

hashish

sticky resin extracted and dried to form a dark- coloured solid

marijuana history

• 6,000 years ago in china

• stems: rope

• seeds: grain

• leaves and flowers: psychoactive and medicinal effects

pharmacology

• psychoactive effects attributable to THC

• THC shows mild affinity for CB1 and CB2

anandamide

• first endogenous cannabinoid to be discovered

• retrograde transmitters

• created in post-synapse

• bind to receptors in pre-synapse

• diffuses freely into the cell membrane

acute psychological effects

• lower dose: increased sense of wellbeing, alterations in perception of space and time and heightened sensations

• higher dose: impairments in episodic and working memory, goal-directed task, and speech production

• acute transient psychosis occurs in some ppl

chronic cognitive effects

• unclear

• working memory function: most reported effect

• rarely present after 4-6 weeks of abstinence

chronic physiological effects: in vitro and primates

• THC and CBD suppress tumour cell proliferation in vitro

• cannabinoids inhibit synapse formation during development → suggested by in vitro studies

• in vivo primate studies failed to show any long term effect of chronic cannabinoid consumption on brain neurochemistry and structure

chronic physiological effects: human studies

• PET studies = chronic cannabis use is associated with down regulation of CB1 receptors

• half grey matter structural imaging studies found no diff

• other half found sig diff but often in opposite directions

• diffusion tensor imaging studies have found consistent diff in interhemispheric tracts (corpus callosum is smaller)

daily high-potency cannabis use associated with

• increased risk for psychosis - more common for males

• earlier onset of psychosis compared to low-potency

• CBD leads to behavioural response in schizo ppl that is similar to atypical antipsychotics

potential for addiction

• 22% of people who use THC meet DSM-5 criteria for cannabis-use disorder (CUD)

• newer high-potency strains of cannabis have greater addictive potential when compared to low-potency cannabis

• high-potency cannabis is associated with 6-7x increased risk of CUD compared to low-potency