Some studies found smoking could be a form of self-medication and heavy smoking patients with schizophrenia had less clinical symptoms than non-heavy smoking patients. However, no studies have reported the relationship between heavy smoking and cognitive symptoms in Chinese patients with schizophrenia.

Prof. ZHANG Xiangyang from the Institute of Psychology of the Chinese Academy of Sciences (CAS) has studied the cognitive symptoms between heavy smoking and non-heavy smoking patients with schizophrenia in the Chinese Han group, and found that heavy smoking patients with schizophrenia had less cognitive symptoms and fewer negative symptoms than non-heavy smoking patients with schizophrenia.

Relevant results were published in European Archives of Psychiatry and Clinical Neuroscience on Apr. 26.

Prof. ZHANG recruited 154 heavy smoking patients and 372 non-heavy smoking patients with schizophrenia. They were asked to complete a detailed questionnaire including general and socio-demographic data. The Positive and Negative Syndrome Scale was rated for psychopathology. The Fagerstrom Test for Nicotine Dependence (FTND) was used to assess the degree of nicotine dependence.

The results showed that heavy smoking patients were younger, started smoking earlier, and had a higher FTND total score than non-heavy smoking patients. Heavy smoking patients had lower negative symptom scores and cognitive factor scores. The cognitive symptoms may be associated with the amount of smoking.

These results support the "self-medication hypothesis". This is the first study to report the relationship between heavy smoking and cognitive symptoms in patients with schizophrenia.

The study was supported by National Natural Science Foundation of China and International Partnership Program of CAS.