How Do Caffeine and Smoking Affect Patients with Schizophrenia?

Two recent studies have shed additional light on caffeine use and smoking in patients with serious mental illness (SMI). One study demonstrated, for the first time, caffeine’s positive effects on neurocognition in male patients with schizophrenia; the other pointed to the efficacy and acceptability of bupropion and varenicline for smoking cessation in adults with SMI.^1,2

An exploratory study by Nunez and colleagues at the University of Barcelona’s Parc Sanitari Sant Joan de Deu assessed the concomitant effects of regular caffeine and smoking on verbal fluency, processing speed, and working, visual, and verbal memory in 113 individuals: 52 hospitalized patients, aged 18 to 65, with schizophrenia, and a control group of 61 participants without mental disease, adjusted to the patient group by gender and age, but whose education levels and scores on the TAP (Testa de acentuacion de palabras) test of verbal IQ  were significantly higher. The study did not match the two groups with respect to the amount of caffeine and tobacco consumed or control for potential confounding variables, such as the use of antipsychotic medication or lifetime history of substance use.¹ Exclusion criteria were a history of alcohol or substance abuse or dependence during the 6 months preceding the study, intellectual disability, brain injury, dementia, severe physical illness, and for the schizophrenia group (the patient group), a history of organic mental disease.

Participants were screened by telephone interview.¹ Caffeine intake was measured as the number of cups of coffee, tea, or other caffeinated drinks ingested per day, and tobacco use was assessed as the number of cigarettes smoked per day. Both were self-reported.¹

The study indicated that male patients with schizophrenia drank significantly more caffeine than did female patients. There was no difference in caffeine intake between the patient and control groups, or between males and females in the control group. Additionally, patients with schizophrenia used significantly more tobacco than participants in the control group. In both groups, males used more tobacco than females.¹

For each performance measure, participants were given two tasks—one more complex than the other. The results demonstrated that, for male patients with schizophrenia, caffeine had a significant positive influence on the performance of the more complex tasks of semantic fluency, cognitive speed, working memory, visual memory of color pictures, but not verbal memory. Caffeine’s positive effects were stronger in younger males than older ones. No effect was noted in female patients with schizophrenia or in participants in the control group.¹ Smoking, on the other hand, had a negative influence on semantic fluency in male patients with schizophrenia. In female patients, no association was observed, and in the control group, results were inconsistent.¹