Cigarette Smoking Increases Risk Of Mental Illnesses

It has always been presumed that individuals who suffer from mental illnesses smoke to self-medicate. But new research reports that the reverse might be true. It states that cigarette smoking could, in fact, raise one’s risk of mental illnesses such as psychosis and depression.

The researchers from the University of Bristol have revealed that lifetime smoking and smoking initiation were both associated risk factors for depression and schizophrenia. Also, genetic liability to depression increased one’s risk of smoking, although the evidence that genetic risk of schizophrenia increasing smoking risk wasn’t all that convincing.

"Smoking is much more common among individuals with mental illness," Medscape Medical News quoted the study’s lead author Robyn Wootton, Ph.D. "Our evidence suggests that this higher prevalence is due to bidirectional effects such that smoking increases risk of developing depression/schizophrenia and also that having depression/schizophrenia increases smoking behavior.”

Although the fact that smoking habit was more common among mental health patients, the cause and effect relationship has been unclear. The author said that it was hard to analyze the causal effects previously since people who smoke might be different from nonsmokers in several ways like eating unhealthy food, drinking more alcohol, therefore making it hard to control for these differences between groups.

The study used the Mendelian randomization model to analyze data from the UK Biobank on more than 460,000 individuals of European ancestry to find out the impact of lifetime smoking on risk for mental health issues like schizophrenia and depression.

They then generated data regarding smoking initiation from the genome-wide association study and identified 378 SNPs (single nucleotide polymorphisms) from 1.232.091 people of European ancestry.

Their findings revealed that higher lifetime smoking was linked to a higher risk of both depression and schizophrenia. They also suggested that one’s higher genetic predisposition for schizophrenia and depression put them at a higher risk of lifetime smoking.

Wootton and his co-authors strongly emphasize that children and adolescents should be informed of this and discouraged from taking up the smoking habit. And for adult smokers, they emphasized the potential psychological and physical benefits of quitting the habit.