Substance Abuse Significantly Raises Risk of Schizophrenia

Substance abuse increases the risk of schizophrenia by 6 times, according to a new study from Denmark.

The results were presented at the International Early Psychosis Association (IEPA) 10th International Conference on Early Intervention in Mental Health.
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Although previous research has suggested substance use increases the risk of schizophrenia, results are controversial due to multiple methodological limitations in those studies.

To better understand how substance abuse impacts schizophrenia risk, the researchers created a cohort from 3,133,968 individuals participating in the Danish registry. The researchers then identified 204,505 individuals diagnosed with substance abuse and 21,305 with schizophrenia.

After a Cox analysis and adjusting for multiple variables, the researchers found that individuals diagnosed with substance abuse were 6 times more likely to develop schizophrenia than the general population.

Cannabis was associated with a 5.2-fold increased risk, alcohol with a 3.4-fold increase, hallucinogenic drugs with a 1.9-fold increase, sedatives with a 1.7-fold increase, amphetamines with a 1.24-fold increase, and other substances with a 2.8-fold increase.

“The risk was found to be significant even 10-15 years subsequent to a diagnosis of substance abuse,” the researchers concluded. “Our results illustrate robust associations between almost any type of substance abuse and an increased risk of developing schizophrenia later in life.”

—Amanda Balbi

Reference:

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. http://www.iepaconference.org/page/?page=oral_sessions. Accessed October 21, 2016.