Factors affecting smoking in schizophrenia.
There is an increased frequency of smoking among patients with schizophrenia. However, it is unknown whether the smoking behavior of the patients is similar in all schizophrenia subtypes, as well as which is the relationship between smoking initiation and disease onset. Four hundred six patients with DSM-IV schizophrenia were interviewed to determine the smoking status in relationship to gender and schizophrenic subtype, and to other factors that could affect or be affected by smoking. The frequency of smoking among patients (58%) was significantly greater than in subjects from the general population (42%) (P =.000005). Male patients smoked significantly more frequently (70%) than the corresponding control subjects (50%) (P =.000006), whereas the difference failed to reach significance between female patients (41%) and control subjects (32%). Among male patients, the number of smokers was significantly greater than in the controls in the paranoid (77%), undifferentiated (72%), and residual (78%) subtypes, whereas there was no significant difference in the disorganized (44%) and catatonic (22%) subtypes. The findings show that the frequency of smoking in schizophrenia patients increases with increasing positive symptoms and decreases with increasing negative symptoms. Male and female smoking patients consumed approximately 10 cigarettes per day more than the corresponding control subjects (P <.000001). In 86% of the patients, smoking initiation occurred before the disease onset. Among patients who smoked, smoking initiation and disease onset occurred at age 18.7 +/- 4.4 and 24.1 +/- 6.1 years, respectively (P <.000001). It appears that smoking in schizophrenia is influenced by gender and subtype. However, the nature of this association remains uncertain because in the vast majority of the patients smoking initiation occurs earlier than the disease onset.