Smokers may be at higher risk of depression and schizophrenia, study finds

Smokers may be at a higher risk of developing depression and schizophrenia, suggesting that smoking can have a greater negative impact on mental health than previously thought. That’s according to research led by scientists from the University of Bristol in the UK.

Rather than merely looking at whether the smokers had a genetic predisposition to mental illnesses such as depression or schizophrenia, researchers used genetic data to examine cause-and-effect relationships with smoking.

"Individuals with mental illness are often overlooked in our efforts to reduce smoking prevalence, leading to health inequalities," the study's lead author, Robyn Wootton, said in a statement.

Scientists studied data from 462,690 individuals of European ancestry. They used an approach called Mendelian randomization to identify genetic variations associated with a trait, such as depression or schizophrenia, then test for changes against an exposure (e.g. smoking) to determine if the relationship is causal.

Researchers found that smoking increased the risk of depression and schizophrenia, and that people with depression and schizophrenia are more likely to smoke. Smoking was also found to increase the risk of bipolar disorder. Because of this, researchers recommended that psychiatric hospitals be smoke-free to avoid detrimental effects on mental health.

The journal Psychological Medicine published the full study.

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