The unaffected first-degree relatives of patients with schizophrenia are more likely to be smokers than individuals without a family history of the disorder, researchers report.
The team also found that relatives of schizophrenia patients who are smokers show greater levels of nicotine dependence than other smokers.
"Our results provide support for the hypothesis that familial factors increase the prevalence of smoking in first-degree relatives of schizophrenic subjects, who have a 'high genetic risk' of schizophrenia," comment Franck Schürhoff (Groupe Hospitalier Mondor-Chenevier, Créteil, France) and team.
"If it can be confirmed that genetic factors make people at risk of schizophrenia more likely to smoke, this would have major implications for our understanding of the etiology of schizophrenia," they add.
The findings come from a study of 98 first-degree relatives of schizophrenia patients and 110 mentally healthy controls without such a family history. The mean age of the relatives was higher than that of controls, at 51.7 versus 41.9 years, but there were no significant between-group differences regarding gender ratios or education levels.
All of the participants were interviewed about smoking, and nicotine dependence was assessed using the Fagerström Test for Nicotine Dependence (FTND). They were also assessed for schizotypal dimensions using the Schizotypal Personality Questionnaire (SPQ).
The researchers found that the prevalence of smoking was greater among the relatives of schizophrenia patients than controls, at 44.9% versus 23.6%.
Furthermore, among smokers, the relatives of schizophrenia patients had higher levels of nicotine dependence than controls, with mean FTND scores of 2.66 versus 1.65.
There were no differences between smokers and nonsmokers in either group regarding mean SPQ scores, at 9.84 versus 12.59 in relatives and 10.70 versus 10.74 in controls. And there was no correlation between nicotine dependence and SPQ score (full score or subscores) in either relatives or healthy controls.
Schürhoff and team conclude in Psychiatry Research: "The relatives of schizophrenic patients are at a greater risk of becoming cigarette smokers. They therefore also have a greater risk of developing chronic health problems. Efforts should therefore be made to prevent nicotine dependence in these relatives and, if necessary, to help them quit smoking if they have already started."
They add: "As some studies have suggested that nicotine may play a role in conversion to psychosis and that heavier smoking is associated with a greater risk of schizophrenia, special psychiatric monitoring could be proposed for young heavy smokers related to schizophrenic subjects, who are at a greater risk of developing schizophrenia."
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