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.
In the second edition of the Diagnostic and Statistical Manual of Mental Disorders, known as DSM-II (1968), the condition was called Hyperkinetic Reaction of Childhood. It was in the 1980 DSM-III that ADD (Attention-Deficit Disorder) with or without hyperactivity was introduced. In 1987 this label was further refined to ADHD (Attention-Deficit Hyperactivity Disorder) in the DSM-III-R and subsequent editions, including the current DSM-5.