Smoking Behavior and its Effect on Psychiatric Symptoms of Patients with Stable Schizophrenia.

Context: Schizophrenia is a common and clinically disabling mental disorder. Many patients with schizophrenia smoke. Research on the effects of smoking on schizophrenia's symptoms are inconsistent.

Objective: The study intended to investigate the smoking status of patients with stable schizophrenia to determine the effects of smoking on schizophrenia-related symptoms.

Design: The research team performed an case-control study.

Setting: The study took place at Beijing Huilongguan Hospital in Beijing, Changping District, China.

Participants: Participants were 160 patients at the hospital who had been diagnosed with stable schizophrenia between April 2018 and March 2020.

Groups: The research team divided participants into two groups based on their current smoking status: (1) a smoking group with 72 participants and (2) a nonsmoking group with 88 participants.

Outcome Measures: The research team: (1) examined the types of antipsychotic drugs that participants received; (2) used a schizophrenia-related scale, the Positive and Negative Syndrome Scale (PANSS), to examine participants' status; (3) examined the smoking habits of the smoking group; and (4) analyzed the correlation between the PANSS score and the smoking group's smoking index.

Results: No significant difference existed between the groups in the type of medicine used (P > .05). The smoking group's PANSS total (P = .014), positive symptom (P = .039), and negative symptom (P = .003) scores were significantly lower than those of the nonsmoking group (P < .05). No significant difference existed between the groups in the general psychopathological symptom score (P > .05). The smoking group started smoking between 13 and 24 years of age, with an mean age of 19.11 ± 4.10 years. The group smoked 10-30 cigarettes/d, with a mean smoking amount of 18.4 ± 3.1 cigarettes/d, and the smoking index was 344.7 ± 48.0. The smoking group's smoking index was significantly negatively correlated with the positive symptom, negative symptom, and total PANSS scores (all P = .000). No correlation existed between the smoking index and the general psychopathological symptom score (P > .05).

Conclusions: Smoking patients with stable schizophrenia generally exhibit fewer symptoms than nonsmoking patients, which relate to the alleviation of mental tension that smoking can provide.