Scientists have discovered that there may be a link between smoking and the development of psychological conditions such as schizophrenia. A new study recently published in The Lancet Psychiatry showed that there appeared to be an association between smoking and the development of schizophrenia. It remains to be seen whether the link is casual or not. Researchers will continue to study the link between the two to glean more information.

The link between smoking and schizophrenia was discovered a while ago, but many researchers chalked up the link to people with schizophrenia simply self-medicating their symptoms by using nicotine for stress relief. However, the authors of the new study decided to carry out a meta-analysis to see whether there might be a link in which smoking actually increases the odds of the development of schizophrenia.

The team reviewed more than sixty previous studies that included nearly 290,000 participants, including almost 15,000 tobacco users and 273,000 non-users. Using this data, they ran statistical analyses to determine connections between the likelihood of having or developing schizophrenia and smoking. The researchers discovered that daily smokers were twice as likely to develop schizophrenia than non-smokers. They also found that daily smokers would develop psychosis about a year earlier than non-smokers.

For some, the finding is not surprising. Researchers have long known that nicotine affects the brain in a variety of negative ways. It has been said that quitting smoking is one of the hardest addictions to kick. The effects of nicotine on the dopamine in the brain may explain the link. According to study author Sir Robin Murray, “Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia. It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.”

This offers opponents of smoking yet another reason to encourage smokers to quit. Schizophrenia is a severe psychiatric disorder that affects around one in 100 people. The condition typically begins in early adulthood and sufferers generally experience disruptions in thinking and perception as well as psychotic experiences. More studies will be needed to understand how nicotine affects the risk of various brain diseases.