New research has found that alcohol, cannabis and other illicit drugs is associated with an increased risk of developing schizophrenia later in life.
The researchers showed that a diagnosis of any substance abuse problem observed a six-fold increase in the likelihood of being diagnosed with schizophrenia.
Cannabis increased the risk by 5.2 times, while alcohol tripled the risk. Other drugs such as hallucinogenic or amphetamines almost doubled the risk.
And the risk was still elevated 10 to 15 years after being diagnosed with substance abuse.
The study, presented at the International Early Psychosis Association meeting, included 3 million people from Danish registers. Two hundred thousand people from the registers were diagnosed with a substance abuse disorder, of which over 21,000 were also diagnosed with schizophrenia.
The data was analysed using various statistical techniques and adjusted for various factors such as gender, other psychiatric diagnoses, parents' socioeconomic status etc.
But it’s impossible to tell if substance abuse causes schizophrenia or is just related.
According to the Centre for Addiction and Mental Health, people with a mental illness are twice as likely to have a substance use problem compared to the general population. And for people with schizophrenia, the number may be as high as 50 per cent.
