When the smoke is gone

Jentien Vermeulen and co-authors recently published 2 articles on smoking in relation to cognitive functioning and symptoms among patients with psychosis in The American Journal of Psychiatry and The Lancet Psychiatry.

Introduction of studies 1,2
The high prevalence of smoking in schizophrenia patients is well known, but long-term findings regarding the association between smoking and cognitive functioning or symptoms are lacking. This is important because the self-medication hypothesis postulates that smoking has a beneficial impact on these outcomes in patients with a psychotic disorder.

A prospective, longitudinal cohort study of patients with non-affective psychosis (N=1,094), their siblings (N=1,047), and healthy control subjects (N=579) was conducted. Participants were interviewed about smoking and tested with a cognitive battery after 3 and 6 years. Furthermore, participants self-rated level of symptoms and quality of life.

At baseline, 66.6% of the patients smoked, compared with 38.3% of the siblings and 25.2% of the control subjects. Smokers showed poorer cognitive performance, higher symptom levels and inferior quality of life compared to non-smokers. Starting to smoke or smoking more cigarettes per day was not associated with long-term improvement of cognition or symptoms. Moreover, quitting smoking was associated with an improvement of speed of processing and starting to smoke was associated with more symptoms in patients.

Clinical implications.
Our findings suggest an absence of cognitive improvement or symptomatic relief by starting to smoke or increasing the number of cigarettes per day, indicating no support for the self-medication hypothesis. This should encourage clinicians to help patients to quit smoking, which may improve patients’ processing speed.

Questions: j.m.vermeulen@amc.uva.nl

Jentien M. Vermeulen, M.D.,  Frederike Schirmbeck, Ph.D., Matthijs Blankers, Ph.D., Mirjam van Tricht, Ph.D., Richard Bruggeman, M.D., Ph.D., Wim van den Brink, M.D., Ph.D., Lieuwe de Haan, M.D., Ph.D.

1.       Association Between Smoking Behavior and Cognitive Functioning in Patients With Psychosis, Siblings, and Healthy Control Subjects: Results From a Prospective 6-Year Follow-Up Study. Am J Psychiat. 2018;175(11):1121-1128.
2.       Smoking, symptoms, and quality of life in patients with psychosis, siblings, and healthy controls: a prospective, longitudinal cohort study. The Lancet Psychiatry. 2019;6(1):25-34.