The findings show that damage to the BG alone can cause disruption of smoking addiction, and when BG damage is combined with INS damage, the disruption increases. The latter finding is consistent with the proposal that the INS has a key role in smoking addiction.

Background There are concerns that varenicline (Chantix/Champix), a prescription medication used to treat smoking addiction, might cause serious neuropsychiatric side effects, such as depression, self-injurious behavior, and suicide. However, the cause of depression and related symptoms in persons who quit smoking after taking varenicline remains uncertain, because smoking cessation itself can cause such symptoms. Method We studied 70 patients with brain lesions: 32 had stopped smoking after suffering their lesion (Quitters) and 38 had kept smoking (Non-Quitters). Results There was no indication of increased depression in the Quitters compared to the Non-Quitters. The 2 groups, which were statistically indistinguishable on demographic and neuropsychological variables, showed the same rates and levels of severity of depression and related symptoms. Moreover, in a subgroup of 16 Quitters who had stopped smoking immediately after their neurological injury in the context of losing their craving to smoke, rates of depression-related symptoms were no higher than in the other Quitters and the Non-Quitters. Conclusions Smoking cessation did not lead to elevated levels of depression in patients with brain lesions, suggesting that psychiatric complications (particularly depression) observed after varenicline use are caused by the medication rather than the smoking cessation itself.