Cigarette Smoking Predicts Development of Depression

It has previously been reported that many adult smokers diagnosed with psychiatric conditions actually started to use nicotine products years before the onset of mental illness such as psychosis. New research findings published in Journal of Affective Disorders indicate that daily nicotine use, mainly cigarette smoking, predicts the future use of antidepressant medication.

The Centers for Disease Control and Prevention estimated that nearly 20% of adults in the US smoked cigarettes in 2011. It is known that individuals diagnosed with neuropsychiatric illness are approximately twice as likely to smoke cigarettes, which often leads to nicotine dependence, compared with persons who do not have a mental disorder.

Additionally, cigarette smoking prevalence among persons with severe mental illness such as major depressive disorder, schizophrenia, or bipolar disorder is approximately 3 times greater than the rate observed in the general population. More specifically, around 66% of patients with schizophrenia, and around 50% of those with bipolar disorder, are current smokers.

In the present study, investigators affiliated with University of Helsinki and University of Eastern Finland linked survey data from the Finnish Twin Cohort Study to the Prescription Register of the Finnish Social Insurance Institute data. This enabled them to evaluate whether cigarette smoking predicts prescriptions of antidepressants in a large sample of twins during a 10-year follow-up. The sample was restricted to only to those individuals who provided data for both cigarette smoking and depressive symptoms. The final sample consisted of 1075 cases (ie, with medication prescriptions) [mean age=43.6 (7.60); 67% female, and 30% daily smokers], and 9577 controls (ie, no medication prescriptions) [mean age=43.7 (7.72); 52% female, and 25% daily smokers]. Researchers adjusted their analyses by controlling for age, gender, social class, other substance use, and health status.

Individuals who reported smoking <20 or ≥20 cigarettes per day were classified as light/moderate or heavy daily smokers, respectively. Findings indicate that the risk of antidepressant medication during the follow-up period, after adjusting for all covariates, was higher for those individuals classified as light/moderate (HR 1.28, 95% CI, 1.03-1.58), or heavy (HR 1.56, 95% CI, 1.17-2.08) daily smokers at the baseline.

These observations are in line with previous reports showing that daily cigarette smoking may be associated with future psychiatric illness; in this case, depression that is severe or moderately severe. Although antidepressant medications are being used to treat psychiatric illnesses other than depression, these findings “highlight the need of carefully and systematically assessing smoking behavior among the patients suffering from or being at risk for developing depressive symptoms,” the authors concluded in their publication.

Reference

Korhonen T, Ranjit A, Tuulio-Henriksson A, Kaprio J. Smoking status as a predictor of antidepressant medication use. J Affect Disord. 2016;207:221-227.