NEW YORK (Reuters Health) – Cigarette smoking is associated with greater decreases in left prefrontal volume in patients with schizophrenia, researchers from Japan report.
“According to the self-medication hypothesis, schizophrenia patients smoke in order to ameliorate cognitive impairment and brain pathology,” Dr. Hidehiko Takahashi from the Graduate School of Medicine of Kyoto University told Reuters Health by email. “Our finding calls into question this hypothesis.”
More than 60% of patients with schizophrenia smoke cigarettes, which is more than double the prevalence in the general population, and some have suggested they do so in an attempt to reduce psychiatric and cognitive symptoms. Studies of the effect of cigarette smoking on brain function and structure have yielded inconsistent findings.
Dr. Takahashi’s team examined gray matter volume in four groups: 20 normal controls with no smoking history, 20 normal controls currently smoking and/or with a past history of smoking, 30 schizophrenia patients with no smoking history, and 30 schizophrenia patients currently smoking and/or with a past history of smoking.
The researchers found no interaction between smoking and schizophrenia, according to the July 14 Schizophrenia Bulletin online report.
Among smokers in general, gray matter volume in the left prefrontal cortex was decreased compared to non-smokers. Among patients with schizophrenia, the volumes of the left prefrontal cortices, left anterior cingulate cortex, left and right hippocampus, right insular and right temporal cortex were decreased compared to normal controls.
In patients with schizophrenia who smoked, left prefrontal cortex volume decreased as pack-years of cigarette smoking increased. Pack-year increases were also associated with increases in positive and negative symptoms of schizophrenia.
In non-smokers with schizophrenia, correlations between left prefrontal cortex volume and positive symptoms of schizophrenia fell short of statistical significance, and there were no significant correlations between left prefrontal cortex volume and negative symptoms of schizophrenia.
“Smoking does not seem to have a positive effect on the brains of schizophrenia patients,” Dr. Takahashi concluded. “Smoking cessation program is encouraged in smokers with schizophrenia.”
Dr. Jasmina Mallet from Fondation FondaMental, Creteil, France and Universite Paris Diderot, who has studied associations between nicotine dependence and schizophrenia, told Reuters Health by email, “I do think that the question of the role of tobacco use for the pathology of schizophrenia is of high relevance, and that the self-medication hypothesis is somehow outdated. The structural MRI alterations found in patients who smoke (with a dose-response effect) don’t support this hypothesis and, therefore, raise interesting research questions, including the possible causality between cigarette smoking and schizophrenia beginning and/or worsening.”
“To my point of view, the main message is that comorbid tobacco use should be evaluated in patients with schizophrenia and, when possible, taken into account in our treatment strategies, in a personalized approach,” she said. “Tobacco use may indeed lead to worsening of brain alterations, already found in schizophrenia, and possibly linked to bad clinical (including cognitive) outcomes.”
“The effects observed in this study underline the need for tobacco withdrawal, whatever the stage of schizophrenia, to ameliorate the prognosis of the disease,” Dr. Mallet concluded. “There is definitely a need for longitudinal studies to better explore the causal links between tobacco and schizophrenia (onset/and course of the disease).”
SOURCE: http://bit.ly/2uQzVel
Schizophrenia Bull 2017.
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