Does smoking reduce akathisia? Testing a narrow version of the self-medication hypothesis

BackgroundThe self-medication hypothesis proposes that schizophrenia patients smoke to decrease their schizophrenia symptoms or antipsychotic side effects, but they usually start smoking before their illness and heavy smoking is not consistently associated with fewer symptoms or side effects. A narrow version of the self-medication hypothesis, heavy smoking reduces akathisia, is explored.MethodThe sample included 250 outpatients with DSM-IV schizophrenia assessed with the Positive and Negative Syndrome Scale (PANSS) and the Barnes Akathisia Scale. Prevalences were 69% (173/250) for smoking, 39% (98/250) for heavy smoking (≥ 30 cigarettes/day), 7% (17/250) for akathisia (Barnes Global score > 1), 14% (35/250) for a broader akathisia definition (Barnes Global score > 0) and 20% for excited symptoms (> 1 on the PANSS factor score).ResultsHeavy smoking was not associated with akathisia (41% of patients with akathisia were heavy smokers versus 39% of patients without akathisia; χ2 = 0.3, df = 1, p = 0.86), even after correcting for confounding factors and/or using a broader akathisia definition. Heavy smoking was associated with excited schizophrenia symptoms (possibly reflecting agitation). Particularly in patients taking lower doses of typical antipsychotics, excited symptoms, with or without akathisia, were strongly associated with heavy smoking and appear to interact with patients' reports of smoking's calming effect as the main reason for smoking.ConclusionThe self-medication hypothesis does not explain increased smoking and heavy smoking in schizophrenia. Moreover, heavy smoking may be associated with more disturbed brain homeostatic mechanisms. Prospective studies need to explore whether temporary increases in cigarette smoking may be associated with periods of higher agitation, with or without akathisia.