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Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.