White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells.
Nicotine dependence is now recognized as a psychoactive substance dependence disorder (DSM-IV, ICD-10). Under the DSM-IV criteria smokers are classified as dependent if they exhibit impaired control and continue to smoke despite awareness that it exacerbates a medical condition, and if they experience withdrawal symptoms when abstaining from smoking, or if they have a history of unsuccessful attempts at quitting.
The diagnosis of alcoholism is often made using the DSM-IV criteria for alcohol dependence, which requires three or more of the following symptoms to occur within the same 12-month period: 1  tolerance, as defined by either of the following: a need for markedly increased amounts of the substance to achieve intoxication or desired effect.