There has long been a link between smoking and mental health conditions.
However, it has not been clear if smoking causes problems or is just more popular among those with poor mental health,
The researchers analysed data from 462,690 people of European ancestry.
They found evidence that tobacco smoking increased the risk of depression and schizophrenia.
Depression and schizophrenia also increased the likelihood of smoking.
The results also showed that smoking rates among with serious mental health conditions are 50% higher than in the general population.
Those with a genetic predisposition towards depression and schizophrenia were also found to be more likely to start smoking, and to smoke more.
Smoking and mental health
The study adds to a growing body of work suggesting that smoking can have adverse effects on mental health.
The same group published a similar study in British Journal of Psychiatry earlier this year, showing evidence that tobacco smoking increases the risk of bipolar disorder.
The UK government’s mental health task force recommended in 2016 that psychiatric hospitals should be smoke free by 2018.
This new evidence adds further weight to support the implementation of smoke-free policies.
Dr Robyn Wootton, the study’s lead author, said: ‘Individuals with mental illness are often overlooked in our efforts to reduce smoking prevalence, leading to health inequalities.
‘Our work shows that we should be making every effort to prevent smoking initiation.
‘We should encourage smoking cessation because of the consequences to mental health as well as physical health.’
Marcus Munafò, professor of biological psychology added: ‘This study shows that genetic studies can tell us as much about environmental influences – in this case the effects of smoking on mental health – as about underlying biology.”
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