Cannabis (Cán-na-bis) is a genus of flowering plants that includes three putative species, Cannabis sativa subsp. indica L., Cannabis sativa subsp. sativa Lam., and Cannabis ruderalis Janisch. These three taxa are indigenous to central Asia and surrounding regions. Cannabis has long been used for fibre (hemp), for medicinal purposes, and as a psychoactive. Industrial hemp products are made from Cannabis plants selected to produce an abundance of fiber and minimal levels of THC (Δ9- tetrahydrocannabinol), one psychoactive molecule that produces the "high" associated with marijuana.
The drug consists of dried flowers and leaves of plants selected to produce high levels of THC. Various extracts including hashish and hash oil are also produced. The cultivation and possession of Cannabis for recreational use is outlawed in most countries.
In a year 2002 review of medical literature, medical cannabis was shown to have established effects in the treatment of nausea, vomiting, unintentional weight loss, and lack of appetite. Other "relatively well-confirmed" effects were in the treatment of "spasticity, painful conditions, especially neurogenic pain, movement disorders, asthma, [and] glaucoma."
Elsewhere it has been shown to be beneficial in treating symptoms associated with treatments for cancer, AIDS, inflammatory bowel disease, and hepatitis.
Cannabis also acts as an antispasmodic and anticonvulsant and is indicated for neurological conditions such as epilepsy especially complex partial seizures, multiple sclerosis, and spasms. As an analgesic and an immunomodulator it is indicated for conditions such as migraine, arthritis, spinal and skeletal disorders.
As a bronchodilator it is beneficial for asthma. It also reduces the intraocular pressure and is indicated for glaucoma. Recent studies have shown the drug to be efficacious in treating mood disorders and mental health issues such as depression, post traumatic stress disorder, clinical depression, attention-deficit disorder, attention-deficit hyperactivity disorder, obsessive-compulsive disorder, panic disorder, Crohn's Disease and bipolar disorder. It is also indicated for premenstrual syndrome, hypertension, and insomnia. It is also reported to be an effective treatment for constipation.