Smoking in schizophrenic patients: A critique of the self-medication hypothesis

Abstract

A common remark among laypeople, and notably also among mental health workers, is that individuals with mental illnesses use drugs as self-medication to allay clinical symptoms and the side effects of drug treatments. Roots of the self-medication concept in psychiatry date back at least to the 1980s. Observations that rates of smokers in schizophrenic patients are multiple times the rates for regular smoking in the general population, as well as those with other disorders, proved particularly tempting for a self-medication explanation. Additional evidence came from experiments with animal models exposed to nicotine and the identification of neurobiological mechanisms suggesting self-medication with smoking is a plausible idea. More recently, results from studies comparing smoking and non-smoking schizophrenic patients have led to the questioning of the self-medication hypothesis. Closer examination of the literature points to the possibility that smoking is less beneficial on schizophrenic symptomology than generally assumed while clearly increasing the risk of cancer and other smoking-related diseases responsible for early mortality. It is a good time to examine the evidence for the self-medication concept as it relates to smoking. Our approach is to focus on data addressing direct or implied predictions of the hypothesis in schizophrenic smokers.

Keywords: Nicotine, Nicotinic receptor, Dopamine, Positive-negative symptoms, Side effects, Age of onset, Smoking cessation

Core tip: The high rates of smoking in mentally ill people have led to the uncritical acceptance that these individuals smoke to self-medicate with nicotine. A self-medication hypothesis (SMH) proposed three decades ago set the stage for explanations for smoking associated with mental illness. Here, we review the origins of the SMH and apply stated and implied predictions to smoking in patients. Our conclusions are that there is some support for the SMH explanations for smoking in schizophrenic patients. However, there are sufficient contradictory data, and predictions not adequately tested, to justify continued empirical studies and new alternative hypotheses to the self-medication concept.