Nicotine dependence linked to symptom severity in schizophrenia

By Mark Cowen, Senior medwireNews Reporter

Nicotine dependence is associated with increased symptom severity in patients with schizophrenia, UK study results show.

The team found that schizophrenia patients with severe nicotine dependence had greater positive symptom severity than nonsmokers, while those with mild-moderate dependence had greater negative symptom severity than nonsmokers.

In turn, greater symptom severity was associated with poorer social adjustment, indicating an indirect link between nicotine dependence and social adjustment, say the authors.

"Although our study does not establish a causal relationship between these variables [nicotine dependence and symptom severity], identifying and treating nicotine dependence may have some value in reducing morbidity and mortality in schizophrenia," they write in the British Journal of Psychiatry.

The researchers studied 131 people diagnosed with schizophrenia who were living in Nithsdale, Scotland, in 2006.

All of the participants were assessed using the Fagerström Test for Nicotine Dependence (FTND), with severe dependence defined as a score greater than 6 and mild-moderate dependence as a score of 6 or less.

In total, 70 (53.4%) patients were current smokers at the time of assessment and 61 were nonsmokers, of whom 21 were exsmokers. Of the smokers, 50 (71%) fulfilled criteria for severe dependence and 20 (29%) for mild-moderate dependence.

Participants with severe nicotine dependence had significantly higher mean scores on the positive subscale of the Positive and Negative Syndrome Scale (PANSS) than nonsmokers, at 12.46 versus 10.38. And patients with mild-moderate nicotine dependence had significantly higher negative subscale scores on the PANSS than nonsmokers, at 16.56 versus 13.32.

The difference in negative subscale PANSS scores between those with severe nicotine dependence and nonsmokers was not significant, nor was the difference in positive subscale scores between patients with mild-moderate nicotine dependence and nonsmokers.

There was a significant association between overall scores on the Social Adjustment Scale Self Report (SAS-SR) and PANSS positive, negative, and general psychopathology subscale scores. Although there was no direct association between SAS-SR scores and smoking dependency, there was an indirect effect, where greater PANSS positive symptom scores mediated the relationship between greater nicotine dependence and worse overall SAS-SR scores.

In the nonsmokers, there was no significant difference between exsmokers and never-smokers regarding PANSS positive and negative subscale scores and SAS-SR scores.

Rajeev Krishnadas (University of Glasgow) and team conclude: "Nicotine dependence was found to be associated with symptom severity and outcome in people with schizophrenia."

They add: "Further systematic longitudinal studies are required to establish whether a causal link exists between nicotine dependence and psychopathology."

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