special subjects
Marijuana (Cannabis)
Pathophysiology
Delta-9-THC binds at cannabinoid receptors, which are present throughout the brain. Any drug that causes euphoria and diminishes anxiety can cause dependence, and marijuana is no exception. High-dose smokers can develop pulmonary symptoms (episodes of acute bronchitis, wheezing, coughing, and increased phlegm), and pulmonary function may be altered, manifested as large airway changes of unknown significance. However, even daily smokers do not develop obstructive airway disease. Recent data suggest that heavy marijuana use is associated with significant cognitive impairment and anatomic changes in the hippocampus, particularly if marijuana use begins in adolescence. There is no evidence of increased risk of head and neck or airway cancers, as there is with tobacco. A sense of diminished ambition and energy is often described. The effect of Marijuana on neonates is not clear. Decreased fetal weight has been reported, but when all factors (eg, maternal alcohol and tobacco use) are accounted for, the effect on fetal weight appears to lessen. However, because safety has not clearly been proved, marijuana should be avoided by pregnant women and those who are trying to become pregnant. THC is secreted in breast milk. Although harm to breastfed infants has not been shown, breastfeeding mothers, like pregnant women, should avoid using marijuana. 