Some of the genes associated with psychiatric disorders like schizophrenia and depression may also be involved in drug use and drug abuse, a new study has found. Appearing in the journal Frontiers in Genetics, the paper even goes as far as to identify connections between certain mental illnesses and the likelihood of using specific substances.
Though it has been assumed for many years that people suffering from psychiatric conditions are often highly prone to drug abuse, hard evidence for a genetic link between the two has remained elusive. To try and uncover such a connection, the study authors analyzed the genomes of 2,573 people, looking for genes related to five different mental illnesses: attention deficit hyperactivity disorder (ADHD), bipolar disorder, autism, depression and schizophrenia.
At the same time, the researchers looked for genes that could be used to predict each person’s level of use of alcohol, marijuana, cocaine, nicotine, and opioids such as heroin or prescription painkillers. Although the genes involved in mental illnesses only appeared to be responsible for about 1 percent of the variation in drug use between participants, the researchers insist that this is significant enough to support the hypothesis of a genetic connection between psychiatric disorders and substance abuse.
"Our research shows that if someone is genetically predisposed towards having a mental illness, they are also prone to use licit and illicit substances and develop problematic usage patterns," explained study co-author Caitlin E. Carey in a statement.
In particular, they found that schizophrenia is associated with severe cocaine and cannabis dependence, as well as general non-problematic cannabis use, while major depressive disorder is linked to alcohol and cocaine addiction. People suffering from bipolar disorder, meanwhile, have an increased genetic predisposition for alcohol, cannabis, cocaine and opioids, although do not necessarily face an enhanced risk of becoming addicted to these drugs.
Lead author of the study Ryan Bogdan commented that “we were fortunate to work with data from individuals recruited for various forms of substance dependence. In addition to evaluating the full spectrum of substance use and misuse, from never-using and non-problem use to severe dependence, this also allowed us to evaluate specific psychiatric disorder-substance relationships".