Various surveys conducted between 2015 and 2019 found that many users of cannabis substitute it for prescription drugs (including opioids), alcohol, and tobacco; most of those who used it in place of alcohol or tobacco either reduced or stopped their intake of the latter substances.Cannabinoid hyperemesis syndrome (CHS) is a severe condition seen in some chronic cannabis users where they have repeated bouts of uncontrollable vomiting for 24–48 hours. Four cases of death have been reported as a result of CHS.A limited number of studies have examined the effects of cannabis smoking on the respiratory system. Chronic heavy marijuana smoking is associated with coughing, production of sputum, wheezing, and other symptoms of chronic bronchitis. The available evidence does not support a causal relationship between cannabis use and chronic obstructive pulmonary disease. Short-term use of cannabis is associated with bronchodilation. Other side effects of cannabis use include cannabinoid hyperemesis syndrome (CHS), a condition which involves recurrent nausea, cramping abdominal pain, and vomiting.Cannabis smoke contains thousands of organic and inorganic chemical compounds. This tar is chemically similar to that found in tobacco smoke, and over fifty known carcinogens have been identified in cannabis smoke, including; nitrosamines, reactive aldehydes, and polycylic hydrocarbons, including benz[a]pyrene. Cannabis smoke is also inhaled more deeply than tobacco smoke. As of 2015, there is no consensus regarding whether cannabis smoking is associated with an increased risk of cancer. Light and moderate use of cannabis is not believed to increase risk of lung or upper airway cancer.
: p104  Aside from a subjective change in perception and mood, the most common short-term physical and neurological effects include increased heart rate, increased appetite, impairment of short-term and working memory, and psychomotor coordination.Additional desired effects from consuming cannabis include relaxation, a general alteration of conscious perception, increased awareness of sensation, increased libido and distortions in the perception of time and space. At higher doses, effects can include altered body image, auditory and/or visual illusions, pseudohallucinations and ataxia from selective impairment of polysynaptic reflexes. In some cases, cannabis can lead to dissociative states such as depersonalization and derealization. Spiritual
Cannabis has held sacred status in several religions and has served as an entheogen – a chemical substance used in religious, shamanic, or spiritual contexts – in the Indian subcontinent since the Vedic period. The earliest known reports regarding the sacred status of cannabis in the Indian subcontinent come from the Atharva Veda, estimated to have been composed sometime around 1400 BCE. The Hindu god Shiva is described as a cannabis user, known as the "Lord of bhang. : p19 In modern culture, the spiritual use of cannabis has been spread by the disciples of the Rastafari movement who use cannabis as a sacrament and as an aid to meditation. Modes of cannabis consumption
Cannabis is consumed in many different ways, all of which involve heating to decarboxylate THCA in the plant into THC.