Alcohol and Cannabis Abuse Linked To Increased Risk of Schizophrenia Interview with:
Dr Stine Mai Nielsen

Copenhagen University Hospital
Mental Health Center Copenhagen
Gentofte, Denmark What is the background for this study? What are the main findings?

Response: Several studies have tested whether use of substances can cause schizophrenia. However due to methodological limitations in the existing literature, uncertainties still remains. We aimed to investigate the association between several types of substance abuses and the risk of developing schizophrenia later in life. We did a nationwide, prospective cohort study using the detailed Danish registers, which enabled us to address some of the limitations from prior findings. Our cohort consisted of more than 3.13 mio. individuals, that we were able to follow up for more than 104 mio. years at risk. We found that dealing with a substance abuse increased the overall risk of developing schizophrenia by 6 times, with abuse of cannabis and alcohol presenting the highest associations (5 and 3 times increased risk). The risk was found to be significant even 10-15 years prior to a diagnosis of substance abuse. What should readers take away from your report?

Response: Our findings confirm the association between abuse of cannabis and schizophrenia found in previous studies. However, we found an association between almost any type of substance abuse and the risk of developing schizophrenia, with alcohol abuse as the most surprising result, as there has not been much evidence of this before. What recommendations do you have for future research as a result of this study?

Response: I believe our findings opens up for many interesting studies regarding the association between alcohol abuse and schizophrenia. Alcohol is one of the substances most used in the world, however I believe it has not been thoroughly examined in the association with psychosis. We are currently looking at parental substance abuse and the offsprings risk of developing schizophrenia later in life. Is there anything else you would like to add?

Response: This study is a part of “The Lundbeck Foundation Initiative for Integrative Psychiatric Research” (iPSYCH), which main goal is to identify the causes of several psychiatric disorders by studying the genetic and environmental factors and thereby find new targets for treatment. Thank you for your contribution to the community.


The results were presented at the International Early Psychosis Association (IEPA) 10th International Conference on Early Intervention in Mental Health.

Nielsen SM, Toftdahl NG, Nordentoft M, Hjorthøj C. Association between alcohol, cannabis and other illicit substance abuse and risk of developing schizophrenia: a nationwide population based register study. Paper presented at: the International Early Psychosis Association (IEPA) 10th International Conference on Early Intervention in Mental Health; Milan, Italy; October 19-22, 2016. Accessed October 21, 2016.

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.
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Last Updated on October 27, 2016 by Marie Benz MD FAAD