(0.01% of smokers). The use of 100 or more cigarettes lifetime is widely used to define a lifetime history of adult cigarette smoking (CDC, 2006). In the broader Australian sample, 51.9% of siblings with a history of smoking met criteria for DSM-IV NW (79.8% of these cases reported four or more symptoms of nicotine withdrawal and the remaining 20.2% reported using nicotine to avoid withdrawal). There were 232 affected sib-pairs (n-1 formula) from 154 families in the Australian linkage sample. In the broader Finnish sample, 41.2% of siblings with history of smoking met criteria for DSM-IV NW (78.4% of these cases reported four or more symptoms of nicotine withdrawal and the remaining 21.6% reported using nicotine to avoid withdrawal). Sixty-eight affected sib-pairs (n-1) were identified from 45 families in the Finnish linkage sample.
