Genetic risk for mental illness linked to substance use and addiction

There are many reports of drug use leading to mental health problems, and we all know of someone having a few too many drinks to cope with a bad day. Many people who are diagnosed with a mental health disorder indulge in drugs, and vice versa. As severity of both increase, problems arise and they become more difficult to treat. But why substance involvement and psychiatric disorders often co-occur is not well understood.

In addition to environmental factors, such as stress and social relationships, a person's genetic make-up can also contribute to their vulnerability to drug use and misuse as well as mental health problems. So could genetic risk for mental illness be linked to a person's liability to use drugs?

This question has been addressed in a new study, published in the open-access journal Frontiers in Genetics.

"Our research shows that if someone is genetically predisposed towards having mental illness, they are also prone to use licit and illicit substances and develop problematic usage patterns," says Caitlin E. Carey, a PhD student in the BRAINLab at Washington University in St. Louis and lead author of this new study. "This is important because if a mental illness, like depression, runs in your family, you are presumed at risk of that disorder. But we find that having a genetic predisposition to mental illness also places that person at risk for substance use and addiction."

This is the first study to compare genetic risk for mental illness with levels of substance involvement across a large sample of unrelated individuals. Rather than analysing family history, Carey and her co-authors used information across each person's genetic code to calculate their genetic risk for psychiatric disorders.

"Previous research on the genetic overlap of mental illness and drug use has been limited to family studies. This has made it difficult to examine some of the less common disorders," says Carey. "For example, it's hard to find families where some members have schizophrenia and others abuse cocaine. With this method we were able to compare people with various levels of substance involvement to determine whether they were also at relatively higher genetic risk for psychiatric disorders."

As well as finding an overall genetic relationship between mental health and substance involvement, the study revealed links between specific mental illnesses and drugs. Dr. Ryan Bogdan, senior author of the study and Director of the BRAINLab, notes, "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". He continues, "For example, we found that genetic risk for both schizophrenia and depression are associated with cannabis and cocaine involvement."

The study opens up new avenues for research evaluating the predictive power of genetic risk. For example, could genetic risk of schizophrenia predict its onset, severity and prognosis in youth that experiment with cannabis and other drugs?

Dr. Bogdan concludes, "It will now be important to incorporate the influence of environmental factors, such as peer groups, neighborhood, and stress, into this research. This will help us better understand how interplay between the environment and genetic risk may increase or reduce the risk of co-occurring psychiatric disorders and substance involvement. Further, it will be important to isolate specific genetic pathways shared with both substance involvement and psychiatric illness. Ultimately, such knowledge may help guide the development of more effective prevention and treatment efforts decades in the future."

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Comments

  1. Stephanie N Marcus Stephanie N Marcus United States says:

    Stop the drug war with objective of shutting down the black market. The drug war has failed. The drug war is driving the problems, not fixing them. Decriminalization/legalization is necessary, it needs to be backed up with public health announcements explaining exactly why it is needed. Its not in any way condoning the abuse of addictors, it is done bc the alternative, the drug war, has made things infinitely worse on almost every level, to include making drugs abundantly available to any & all that wants them.
    We need to pull LE out of the drug biz - that will free up a lot of resources currently chasing their collective tails. When the laws create more harm and cause more damage than they prevent, its time to change the laws. The $1 TRILLION so-called war on drugs is a massive big government failure - on nearly every single level. Its way past time to put the cartels & black market drug dealers out of business. Mass incarceration has failed. We cant even keep drugs out of a contained & controlled environment like prison.
    We need the science of addiction causation to guide prevention, treatment, recovery & public policies. Otherwise, things will inexorably just continue to worsen & no progress will be made. Addiction causation research has continued to show that some people (suffering with addiction) have a "hypo-active endogenous opioid/reward system." This is the (real) brain disease, making addiction a symptom, not a disease itself. One disease, one pathology. Policy must be made reflecting addiction(s) as a health issue.
    The war on drugs is an apotheosis of the largest & longest war failure in history. It actually exposes our children to more harm & risk and does not protect them whatsoever. In all actuality, the war on drugs is nothing more than an international projection of a domestic psychosis. It is not the "great child protection act," its actually the complete opposite.
    The lesson is clear: Drug laws do not stop people from harming themselves, but they do cause addicts to commit crimes and harm others. We need a new approach that decriminalizes the disease. We must protect society from the collateral damage of addiction and stop waging war on ourselves. We need common sense harm reduction approaches desperately. MAT (medication assisted treatment) and HAT (heroin assisted treatment) must be available options. Of course, MJ should not be a sched drug at all.
    Every human being is precious, worthy of love and belonging, and deserves opportunities to fulfill his or her potential regardless of past trauma, mental and emotional anguish, addictive behaviors or mistakes made.

  2. Mark Rojek Mark Rojek United States says:

    One area of failed research has been the connection of pesticides, herbicides and heavy metal exposure leading to possible genetic alterations and/or mental illness. There are about 65,000 chemicals in the environment that have NEVER been tested individually, let alone in combination. Aluminum and mercury are both known to be neurotoxins in humans other mammals, fish, reptiles and insects. What about all the other chemicals? NO ONE has taken the time to test these substances for their neurotoxic or possible genetic effects. Why not? Time to open up research into this area and see just how we have been poisoning ourselves.

  3. Ref
    Gianvito Lagravinese Gianvito Lagravinese Sweden says:

    Where are the references to the study?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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