Severe Mental Illness Tied to Substance Use: Which Comes First?


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Cigarette smoking is common in people with psychotic disorders. Image by lorettaflame.

Cigarette smoking is common in people with psychotic disorders. Image by lorettaflame.

Do you need another reason to stop using alcohol, tobacco, marijuana, or illegal drugs? New research indicates that substance abuse may lead to serious mental conditions such as schizophrenia and bi-polar disorder with psychosis.  With the help of a large data base called the Genomic Psychiatry Cohort, researchers have begun to shed light on the connection between alcohol and drug abuse, dependence, and mental illness.

Dr. Sarah Hartz and colleagues from Washington University in St. Louis, Missouri collaborating with researchers from the University of Southern California investigated the relationship between drug use and serious mental illness.  Some of the findings were surprising.

The Study Design: Drawing from the Genomic Psychiatry Cohort

Previous research indicated that those with mental illness often had co-occurring problems with alcohol.  In 2002 the National Institute of Alcoholism and Alcohol Abuse concluded “[t]he chance of having a psychiatric disorder is significantly increased among people with alcohol dependence but not among those with alcohol abuse.” But no researchers had conducted a large-scale study specifically examining drug use and psychosis.

MedicineNet defines psychosis as ” a mental illness  that markedly interferes with a person’s capacity to meet life’s everyday demands.  In a specific sense, it refers to a thought disorder in which reality testing is grossly  impaired… Symptoms can include seeing, hearing, smelling, or  tasting things that are not there; paranoia; and delusional thoughts.”

Interestingly, MedicineNet warns that most professionals don’t consider psychosis brought about by drug use as “true psychosis.”  This conundrum, the relationship between mental illness, psychosis, and chronic drug use is the target of Hartz’s research.

9142 individuals with psychotic disorders such as schizophrenia and bio-polar disorder with psychotic features who were already enrolled in the Genomic Psychiatry Cohort provided information on their drug use.  The Genomic Psychiatric Cohort, or GPC, is a multi-instuitional collaboration drawing on people obtaining treatment at a variety of mental health institutions. Participants answered questions about tobacco, alcohol and drugs.

The researchers compared answers from those suffering with psychosis (cases) to answers provided by members of the general population without a diagnosis of severe mental illness (controls).  The study provided modest compensation to those participating.

High Rates of Substance Use Among those with Psychosis

The researchers found among individuals with psychotic disorders, all races and sexes showed “greatly elevated risks for smoking and alcohol, marijuana and drug use.”

Self-medication by those with mental illness is a possible cause for the increased use of substances. However, in an exclusive interview with Decoded Science, the lead researcher, Dr. Susan Hartz, stated, “Many people with severe mental illness report self-medicating as the reason for smoking, drinking alcohol, or using other substances, but people start using substances (tobacco, alcohol, marijuana) in their mid-teens, prior to the development of symptoms of the mental illness…In addition, people with severe mental illness who smoke, drink or use other substances do worse overall than people who don’t use any substances—i.e. the substances make the mental illness worse, suggesting that self-medication isn’t working…”

Dr. Hartz concludes, “I think the most likely explanation is that substance use contributes to the development of severe mental illness (many people can use substances without developing severe mental illness, but use of substances helps trigger severe mental illness).”

In other words, using alcohol, tobacco, marijuana, and other substances can contribute to the development of mental illnesses such as schizophrenia and bi-polar disorder.

Drug Use: Implications for Policy Makers


Marijuana use is associated with schizophrenia. Image by normalityrelief

Hartz and colleagues found the strongest association between psychosis and cigarette smoking.  Alarmingly, public health initiatives that have decreased smoking among those under 30 years old in general public have been “ineffective in individuals with severe psychotic illness.” Since anti-smoking campaigns appear not to have influenced those who become psychotic, public health officials need to design specialized campaigns to reach this population.

The study also implicated marijuana: “marijuana use at age 16 years was associated with psychosis at age 19 years.”  As the movement for legalization of marijuana expands with recreational use of pot made legal in Colorado and medicinal use legalized in 20 states and the District of Columbia, the use of marijuana and other drugs by young people poses concerns.

Dr. Hartz  worries, “Although adolescents can look like adults, the brain develops rapidly until age 25. I think we should use all our resources to help keep tobacco, alcohol, marijuana and other substances away from teenagers and young adults to help prevent mental illness and addiction.”

Drug Use or Psychosis: Which Came First?

Whether psychosis results from drug use, or simply co-exists with drug use, the recommendations remain the same.  The most prudent policy would be to encourage people, especially youth,  to abstain from abuse of tobacco, marijuana, drugs and alcohol.

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