Cigarette smoking reduces medication-associated deficits in reward processing in patients with schizophrenia

Imaging studies have demonstrated that reward paradigms allow investigating the mesolimbic-mesocortical dopaminergic dysfunction in schizophrenia as the system is activated upon expectation and receipt of rewards. Altered activation of dopaminergic brain areas but also paralleling behavioural changes were found [1]: the reward-related acceleration of reaction times as found in healthy controls was only present upon high, but not low rewards in patients. However, the low number of participants of the imaging study made it difficult to link the findings to medication or psychopathology. To overcome this, we used a mere behavioural approach and investigated 49 medicated patients with a diagnosis of schizophrenia (ICD-10 F20) and 49 healthy controls. Subjects were instructed to react with a certain button press to two different stimuli to have a 60% chance to win a previously announced amount of money ($1.00 or $ 0.20). The prior finding of a missing acceleration of reaction times in patients upon low rewards was replicated. The effect was pronounced in the non-smoking subgroup of patients were we also found a positive correlation with type of medication (D2-receptor-blockage or not) and by trend with the PANSS scores. In line with clinical observations, our findings support the notion that smoking reduces medication-associated side effects in patients with schizophrenia, here in the form of deficient reward processing. References: [1] Walter H et al, Psychopharmacol 2009; 206: 121–32