Figure 3. Mean cigarette craving for positive reinforcement no nicotine deprivation [A] and 12 hours nicotine deprivation [B] and for withdrawal relief no nicotine deprivation [C] and nicotine deprivation [D] across the 2-hr ad-lib smoking period by diagnosis (schizophrenic smokers vs. control smokers) and medication (mecamylamine vs. placebo).