Cannabis is now legal to purchase and use in the state of Washington. However the psychiatric benefits and consequences to use are still poorly understood. Below are some facts that are known about marijuana, which are contrary to public wisdom.
Cannabis is not just one substance but many.
The marijuana plant contains numerous psychoactive substances, called cannabinoids, in varying amounts depending on the strain of plant, age at harvesting, plant part, and growing conditions. Preparation of cannabis can further alter the concentration of these substances. There are 85 known cannabinoids, the best known of which are tetrahydrocannabinol (THC) and cannabidiol (CBD). This variability makes cannabis difficult to study medically and casts doubt on claims as to its medical benefits. CBD has anxiolytic and sedating effects, whereas THC has stimulant, euphoric and hallucinogenic effects. However, the presence of numerous other cannabinoids with unknown effects makes it difficult to select a cannabis product for any desired psychiatric effect.
Cannabis is addictive.
Common wisdom stated that one cannot become “addicted” to marijuana, as one would to alcohol, opioids or stimulants. However research has shown that there is indeed physical dependence, with both tolerance and withdrawal. With occasional use, the risk for dependence is low. However the more frequent or the younger the age at use, the risk of dependence increases markedly, with 17% of adolescents and over 25% of daily users developing dependence. Withdrawal symptoms after regular use include irritability, anorexia, anxiety and insomnia. Users can also develop tolerance, which is characterized by needing larger amounts of a substance to gain the same effect.
Cannabis use poses psychiatric risks with unclear benefits.
Clinical trials and metanalyses have shown benefit for chronic pain and for muscle spasm in multiple sclerosis. There is no convincing evidence to date for use in other medical disorders or psychiatric ones. Adverse effects of use have been more conclusively demonstrated however. Physical risks of cannabis use include infertility, pulmonary disease (from both smoked and vaporized forms), cardiovascular risks including increased risk of strokes and myocardial infarction, and prenatal effects. Although cannabidiol provides anxiolytic effects, as explained above cannabis contains numerous other cannabinoids with varying effects, and in general use is associated with increased incidence of anxiety disorders and more severe anxiety symptoms Cannabis use has been shown to worsen the course of PTSD in veterans. Studies have also found associations with depression and mania. Cannabis use has a clear link to schizophrenia, with adolescents who regularly use it having a two-fold increase in the risk of developing that disorder. It has been linked to deficits with attention, executive function and memory. The effects have been seen in both neuropsychiatric testing as well as in imaging with reduction in the volume of the hippocampus and amygdala, the two parts of the brain most involved in memory.
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Wilkinson ST. Marijuana use is associated with worse outcomes in symptom severity and violent behavior in patients with posttraumatic stress disorder.
NIDA (National Institue on Drug Abuse) www.drugabuse.gov