How does nicotine affect mental health. What is the connection between vaping and depression. Can e-cigarette use lead to anxiety symptoms. Is there a link between vaping and ADHD. How does quitting vaping improve mental well-being.

The Concerning Relationship Between Vaping and Depression

Recent studies have unveiled a troubling connection between e-cigarette use and depression. A comprehensive 2019 JAMA study examining nearly 30,000 adult e-cigarette users found that current vapers have double the odds of receiving a depression diagnosis compared to those who have never vaped. Even more alarming, frequent vapers face 2.4 times higher odds of a depression diagnosis.

Why might vaping be linked to depression? Researchers have proposed several potential mechanisms:

• Nicotine’s effect on brain chemistry and neurotransmitter balance
• The presence of trace metals in e-liquids that may impact mood regulation
• Potential withdrawal symptoms leading to depressive episodes
• Social and lifestyle factors associated with vaping behavior

While correlation doesn’t necessarily imply causation, these findings highlight the need for further research into the long-term mental health impacts of e-cigarette use.

Vaping and Its Effects on Anxiety Symptoms

Anxiety is another mental health concern that appears to be associated with vaping. The same JAMA study revealed that current e-cigarette users had 1.67 times higher odds of reporting at least one day of poor mental health in the past month compared to never-users. This suggests a potential link between vaping and increased anxiety or stress levels.

A 2019 study focusing on college students found a significant association between vaping and higher levels of anxiety symptoms. Nicotine dependence, in particular, was correlated with greater anxiety. This raises questions about the role of nicotine in exacerbating anxiety disorders or contributing to their development.

The Anxiety-Vaping Cycle

Is vaping causing anxiety, or are anxious individuals more likely to vape? The relationship may be bidirectional:

1. Nicotine’s stimulant effects can mimic or worsen anxiety symptoms
2. Some individuals may use vaping as a coping mechanism for existing anxiety
3. Nicotine withdrawal between vaping sessions can increase feelings of anxiousness
4. The social stigma or health concerns surrounding vaping may contribute to anxiety

The Emerging Link Between Vaping and ADHD Symptoms

Attention-Deficit/Hyperactivity Disorder (ADHD) is another area of concern when it comes to vaping and mental health. The 2019 study on college students not only found links to anxiety but also revealed a significant association between vaping and higher levels of ADHD symptoms.

Are individuals with ADHD more susceptible to nicotine addiction? Research suggests this may be the case, as the stimulant properties of nicotine can temporarily improve focus and attention. However, this can lead to a dangerous cycle of dependence and potentially worsen ADHD symptoms in the long run.

Potential Mechanisms Linking Vaping and ADHD

• Nicotine’s effect on dopamine pathways in the brain
• Impulsivity associated with ADHD increasing the likelihood of experimentation with vaping
• Self-medication attempts to manage ADHD symptoms
• Potential exacerbation of attention problems due to nicotine withdrawal

The Impact of Vaping on Adolescent Mental Health

While the effects of vaping on mental health are concerning for all age groups, adolescents are particularly vulnerable. A 2017 study focusing on ninth-graders in Los Angeles found that those who used e-cigarettes at a higher frequency were associated with increased depressive symptoms a year later, including feelings of sadness and crying spells.

Why are teenagers at higher risk? Several factors contribute to this increased vulnerability:

• The developing adolescent brain is more susceptible to the effects of nicotine
• Hormonal changes during puberty can intensify mood fluctuations
• Social pressures and identity formation make teens more prone to peer influence
• Limited coping skills may lead to vaping as a maladaptive stress response

These findings underscore the importance of preventing e-cigarette use among young people and providing support for those already struggling with nicotine dependence.

The Dual Threat: Nicotine and THC Vaping on Mental Health

Recent research has expanded our understanding of how vaping affects mental health by examining the combined impact of nicotine and THC (tetrahydrocannabinol, the psychoactive component in marijuana) vaping. A study of over 2,500 individuals aged 13-24 revealed concerning trends:

• Nicotine-only vapers, THC-only vapers, and dual vapers (using both substances) were more likely to report anxiety symptoms, depressive symptoms, and suicidal thoughts compared to non-vapers
• Approximately 60% of nicotine-only, THC-only, and dual vapers reported experiencing anxiety symptoms, compared to about 40% of non-vapers
• Over half of the nicotine-only, THC-only, and dual vapers reported experiencing symptoms of depression, versus 25% of non-vapers

These findings highlight the potential compounded risks of using multiple substances through vaping, particularly for young people whose brains are still developing.

The Interplay Between Nicotine and THC

How do nicotine and THC interact to affect mental health? Several mechanisms may be at play:

1. Both substances can alter neurotransmitter balance in the brain
2. Combined use may intensify mood swings and emotional instability
3. The addictive potential of both substances can lead to increased dependence
4. Withdrawal from multiple substances may exacerbate mental health symptoms

Breaking the Cycle: The Mental Health Benefits of Quitting Vaping

While the links between vaping and mental health concerns are troubling, there is hope. Research suggests that quitting vaping can lead to significant improvements in mental well-being. A 2014 meta-analysis showed that quitting smoking (which can be extrapolated to vaping) is associated with lower levels of anxiety, depression, and stress, as well as improved mood and quality of life compared to continuing the habit.

What mental health improvements can individuals expect when they quit vaping?

• Reduced anxiety and stress levels as nicotine withdrawal symptoms subside
• Improved mood stability and emotional regulation
• Enhanced self-esteem and sense of accomplishment
• Better sleep quality, which positively impacts mental health
• Increased energy levels and motivation

Strategies for Successfully Quitting Vaping

Quitting vaping can be challenging, but there are numerous strategies and resources available to support individuals on their journey to better mental health:

1. Seek professional help from a healthcare provider or mental health specialist
2. Utilize nicotine replacement therapy (NRT) under medical supervision
3. Join support groups or counseling programs specifically designed for quitting vaping
4. Practice stress-reduction techniques like meditation, yoga, or deep breathing exercises
5. Engage in regular physical activity to boost mood and manage cravings
6. Identify and avoid triggers that lead to vaping urges
7. Develop a strong support network of friends and family

The Role of Prevention and Education in Protecting Mental Health

Given the emerging evidence linking vaping to various mental health concerns, prevention and education play crucial roles in protecting individuals, especially young people, from the potential risks. Comprehensive approaches to addressing this issue include:

• School-based education programs on the dangers of vaping and its impact on mental health
• Public awareness campaigns targeting both youth and adults
• Stricter regulations on e-cigarette marketing and sales, particularly those targeting young people
• Integration of vaping prevention into existing mental health and substance abuse programs
• Increased funding for research on the long-term mental health effects of vaping
• Training for healthcare providers to effectively screen for and address vaping-related mental health issues

The Importance of Early Intervention

Early intervention is key to preventing the potential long-term mental health consequences of vaping. How can we identify and support individuals at risk?

1. Implement regular mental health screenings in schools and healthcare settings
2. Train educators and parents to recognize signs of vaping and associated mental health symptoms
3. Develop peer support programs to encourage healthy coping mechanisms
4. Provide easily accessible resources for those seeking help to quit vaping
5. Address underlying mental health concerns that may contribute to vaping behavior

Future Directions in Vaping and Mental Health Research

As our understanding of the relationship between vaping and mental health continues to evolve, several key areas require further investigation:

• Long-term studies on the mental health trajectories of individuals who vape
• Research into the specific components of e-liquids that may impact mental health
• Exploration of potential genetic factors that influence susceptibility to vaping-related mental health issues
• Development and evaluation of targeted interventions for individuals with co-occurring vaping and mental health concerns
• Investigation of the potential differences in mental health impacts between various types of e-cigarette devices and products

Emerging Technologies and Mental Health Support

How can technology be leveraged to address the mental health challenges associated with vaping?

1. Development of mobile apps for mood tracking and vaping cessation support
2. Virtual reality interventions for managing cravings and stress
3. AI-powered chatbots providing 24/7 support and resources
4. Wearable devices that monitor physiological markers of stress and nicotine use
5. Online communities and forums for peer support and shared experiences

As research in this field progresses, it is crucial to remain vigilant about the potential mental health impacts of vaping while working towards effective prevention and treatment strategies. By addressing this issue from multiple angles – including education, policy, healthcare, and technology – we can strive to protect individuals’ mental well-being and reduce the burden of vaping-related mental health concerns on society as a whole.

3 ways vaping affects mental health

News Article

Topic

• Targeted Communities

Subtopic

• Mental Health

While it is well known that nicotine harms developing brains, including by making young people more susceptible to addiction, lesser known are the worrying connections between nicotine and mental health.

Though nicotine has not been found to directly cause mental health conditions, peer-reviewed studies reveal troubling links between vaping, nicotine, and worsening symptoms of depression and anxiety, as well as higher odds of having a depression diagnosis. Here are three ways vaping affects mental health.

Current e-cigarette users have double the odds of having a diagnosis of depression compared to those who have never vaped

Can vaping cause depression and anxiety?

According to a 2019 JAMA study of nearly 30,000 current e-cigarette users above age 18, frequent vaping is tied to even higher odds – 2. 4X – of having a diagnosis of depression compared to never users.

The study also showed current e-cigarette users had 1.67X higher odds and former e-cigarette users had 1.52X higher odds of reporting at least one day of poor mental health in the past month compared to never users who reported no days of poor mental health. Researchers also believe that trace metals in vape liquid may play a role in the potential link between vaping and depression.

Vaping can worsen symptoms of depression

Does vaping make you depressed?

Based on the results of a 2017 study of nearly 2,500 ninth graders who had never previously used e-cigarettes or combustible tobacco in Los Angeles, those who used e-cigarettes at a higher frequency were associated with higher depressive symptoms. This also included feeling sad or having crying spells – a year later.

Nicotine use is significantly associated with higher levels of conditions like ADHD

Does vaping cause ADHD?

A 2019 study of U. S. college students found that vaping is significantly associated with higher levels of ADHD symptoms, and nicotine dependence was correlated with greater anxiety symptoms.

It is critical to both prevent teens and young adults from vaping or smoking and to help those who are addicted to quit as soon as possible. Not only does quitting break the addiction to nicotine and reduce health-related risks associated with tobacco use, it can also improve mental health. A 2014 meta-analysis showed quitting smoking is linked with lower levels of anxiety, depression and stress as well as improved positive mood and quality of life compared with continuing to smoke. This is Quitting^® is a free and anonymous quit resource from Truth Initiative that has helped more than 350,000 on their journey to quit vaping.

For free help with quitting vaping, text DITCHVAPE to 88709.

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Rising vaping rates among lesbian, gay, and bisexual young people outpace peers, widening tobacco use gap

Depression & anxiety symptoms linked to vaping nicotine and THC in teens and young adults

Research Highlights:

• A study of more than 2,500 people ages 13-24 found that nicotine-only vapers, THC-only vapers and dual vapers (of nicotine and THC) were more likely to report anxiety symptoms, depressive symptoms and suicidal thoughts when compared with their peers who did not use electronic cigarettes or vape THC.
• Approximately 60% of the nicotine-only, THC-only and dual vapers self-reported that they experienced anxiety symptoms, versus about 40% of participants who never vaped. Anxiety symptoms were more frequently reported among THC-only vapers.
• Over half of the nicotine-only, THC-only and dual vapers self-reported that they experienced symptoms of depression versus 25% of non-vapers.

Embargoed until 3 p.m. CT/4 p.m. ET, Tuesday, February 28, 2023

DALLAS, February 28, 2023 — A survey of more than 2,500 teens and young adults led by the American Heart Association found that vaping nicotine and THC, the psychoactive component in marijuana, was associated with self-reported symptoms of depression and anxiety. The study’s preliminary findings will be presented at the Association’s Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Scientific Sessions 2023, which will be held in Boston, February 28-March 3, 2023, and offers the latest science on population-based health and wellness and implications for lifestyle and cardiometabolic health.

The use of pod-based e-cigarettes has surged among youth and young adults in recent years. Previous studies have identified links between vaping and symptoms of both anxiety and depression among young adults.

“Younger people have long been vulnerable to tobacco use, may experience greater harm from nicotine and other drugs and may be targeted by tobacco advertisers and marketers,” said study author Joy Hart, Ph.D., a professor of communication at the University of Louisville in Kentucky. “E-cigarette devices are still relatively new compared to other tobacco products, such as combustible cigarettes and pipes, so more research is needed to try to better understand the popularity of e-cigarettes, including reasons for vaping and the associated health risks among youth.”

The researchers, several of whom work for the Association, conducted an online survey among 2,505 teens and young adults, ages 13-24, to gauge mental health differences among nicotine-only vapers, THC-only vapers, dual vapers of both nicotine and THC and people who had never vaped any product. The study was focused on 1,921 people who had never vaped or were current vapers, defined as having vaped in the past 30 days. Of those participants, 562 individuals reported they had never vaped, 370 had vaped only nicotine, 159 had vaped only THC, and 830 were dual vapers of nicotine and THC.

The analysis of the participants’ survey responses found:

• Approximately 70% of the THC-only vapers and 60% of the nicotine-only vapers and dual vapers reported experiencing anxiety symptoms — such as worries, flashbacks, panic attacks and situational anxieties— within the past week, compared to about 40% of participants who had never vaped.
• Over half of the nicotine-only vapers, THC-only vapers and dual vapers reported experiencing symptoms of depression — such as difficulty engaging in or being interested in activities normally enjoyed, whether they felt that depression interfered with their ability to do the things they needed to do at work, at school or at home and whether depression interfered with their social life and relationships — within the past week, compared to 25% of non-vapers.
• More than 50% of people in all vaping groups reported having suicidal thoughts within the past 12 months, compared to only one-third of the non-users.
• About a quarter of the dual vapers and nicotine-only vapers started vaping nicotine to calm down or feel less stressed, and one-third of participants in both groups reported that they currently vaped nicotine to cope with feelings of anxiety. In contrast, about half of THC-only vapers started vaping THC and currently vaped THC to relieve anxiety symptoms.
• Around 20% of nicotine-only vapers and dual vapers started vaping to help feel less depressed and currently vaped for this reason. About one-third of THC-only vapers started vaping THC and nearly half currently vaped TCH to feel less depressed.

Dual vapers were significantly more likely than nicotine-only vapers to indicate addiction to nicotine, which was defined in this study as behavior such as waking up at night to vape. Dual vapers of nicotine and THC were also significantly more likely to say they felt less depressed after they started vaping, whereas nicotine-only vapers were more likely to report that vaping had no impact on their feelings of depression. This may be related to dual users’ stronger addiction to these products, rather than the positive impacts of the products on their mental health, the researchers said.

“Although we knew that THC was commonly vaped, we were surprised to have so many dual vapers—more than double the nicotine-only vapers. Dual use may either compound the addictive nature of vaping or attract people who are more prone to addiction, as well as have an impact on symptoms of depression. These findings suggest the importance of addressing the use of THC and the need for building resilience and coping skills for teens and young adults,” Hart said.

The study had limitations: the use of cross-sectional data did not allow researchers to assess whether symptoms of anxiety and depression, as well as suicidal thoughts, were caused or exacerbated by the use of the THC and nicotine vapes, or whether the existence of those symptoms had an effect on the use of the vape products; collecting online data via a web-based panel meant that participants may not be representative of all U. S. teens and young adults; and the data were self-reported.

“When better coping skills are developed, there may be fewer temptations to try to manage anxiety symptoms and similar mental health challenges through vaping, as well as better refusal skills if offered an electronic cigarette. Increased priority on more positive behaviors to alleviate tension and manage anxiety symptoms may reduce the likelihood of vaping, possible addiction and the increased risk of negative health outcomes,” said Rose Marie Robertson, M.D., FAHA. Robertson is deputy chief science and medical officer of the American Heart Association, co-director of the Association’s National Institutes of Health/U.S. Food and Drug Administration-funded Tobacco Center of Regulatory Science and senior author on the study. “There is also an urgent need for effective communication campaigns and educational programs to increase understanding among youth and young adults of the risks of using e-cigarettes.”

Future research, Robertson said, is needed to examine the long-term connections between mental health and vaping, whether nicotine-only, THC-only or both nicotine and THC.

“This study showed the striking significance of issues with mental health in users of both nicotine vapes as well as THC vapes, and as new products continue to come on the market, I think that this is something that we will continue to see,” said Loren E. Wold, Ph.D., FAHA. Wold is assistant dean for biological health research in the College of Nursing, a professor in the Colleges of Nursing and Medicine (physiology and cell biology) at The Ohio State University and lead of the writing committee for the Association’s 2022 Statement on Cardiopulmonary Consequences of Vaping in Adolescents. “These products were developed as smoking cessation tools for those that use traditional cigarettes, so I’m very curious now what the implications are with mental health in users who are using these products to help stop smoking.”

Additional co-authors are Jeffrey Willett, Ph.D.; Allison Groom, M.A.; Robyn L. Landry; Angel Bassett, M.A.; Mary Dunn, Ph.D.; Kandi Walker, Ph.D.; Thomas Payne, Ph. D.; and Anshula Kesh, M.P.H., B.D.S. Authors’ disclosures are listed in the abstract.

The study was funded by a grant from the Kaiser Permanente National Community Benefit Fund at the East Bay Community Foundation. Through the American Heart Association Tobacco Center for Regulatory Science, the Association works closely with investigators at institutions across the country to pursue research that adds to the existing knowledge about the health impacts of smoking and nicotine-related products including e-cigarettes, findings that can help inform public health and the regulation of tobacco products.

Statements and conclusions of studies that are presented at the American Heart Association’s scientific meetings are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. Abstracts presented at the Association’s scientific meetings are not peer-reviewed, rather, they are curated by independent review panels and are considered based on the potential to add to the diversity of scientific issues and views discussed at the meeting. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.

The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers and the Association’s overall financial information are available here.

Additional Resources:

• Multimedia is available on the right column of release link https://newsroom.heart.org/news/depression-anxiety-symptoms-linked-to-vaping-nicotine-and-thc-in-teens-and-young-adults?preview=c30b14f8eb24c1a3519f6e7e9e0d0513
  
  • Video interview: Rose Marie Robertson, M.D., FAHA, senior author on the study and deputy chief science and medical officer of the American Heart Association and co-director of the Association’s National Institutes of Health/U. S. Food and Drug Administration-funded Tobacco Center of Regulatory Science.
  • Video interview: American Heart Association volunteer expert, Loren E. Wold, Ph.D., FAHA, assistant dean for biological health research in the College of Nursing, a professor in the Colleges of Nursing and Medicine (physiology and cell biology) at The Ohio State University and lead of the writing committee for the Association’s 2022 Statement on Cardiopulmonary Consequences of Vaping in Adolescents.

• AHA news release: Use of e-cigarettes had negative cardiovascular effects similar to smoking cigarettes (October 2022)
• AHA news release: People who vape had worrisome changes in cardiovascular function, even as young adults (October 2022)
• AHA news release: No health benefits among adults who used both e-cigarettes and traditional cigarettes (May 2022)
• AHA health information: Quit Vaping – Quit Smoking – Quit Tobacco
• AHA health information: The Ugly Truth About Vaping
• For more news from AHA EPI Lifestyle Conference 2023, follow us on Twitter @HeartNews #EPILifestyle23.

The American Heart Association’s EPI/LIFESTYLE 2023 Scientific Sessions is the world’s premier meeting dedicated to the latest advances in population-based science. The meeting will be held Tuesday-Friday, February 28 – March 3, 2023, at the Omni Boston Seaport in Boston, Massachusetts. The primary goal of the meeting is to promote the development and application of translational and population science to prevent heart disease and stroke and foster cardiovascular health. The sessions focus on risk factors, obesity, nutrition, physical activity, genetics, metabolism, biomarkers, subclinical disease, clinical disease, healthy populations, global health and prevention-oriented clinical trials. The Councils on Epidemiology and Prevention and Lifestyle and Cardiometabolic Health (Lifestyle) jointly planned the EPI/Lifestyle 2023 Scientific Sessions. Follow the conference on Twitter at #EPILifestyle23.

About the American Heart Association

The American Heart Association is a relentless force for a world of longer, healthier lives. We are dedicated to ensuring equitable health in all communities. Through collaboration with numerous organizations, and powered by millions of volunteers, we fund innovative research, advocate for the public’s health and share lifesaving resources. The Dallas-based organization has been a leading source of health information for nearly a century. Connect with us on heart.org, Facebook, Twitter or by calling 1-800-AHA-USA1.

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For Media Inquiries and AHA Expert Perspective:

AHA Communications & Media Relations in Dallas: 214-706-1173; [email protected]

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Scientists have found out how smoking and depression are connected

Smoking can lead to depression, Israeli scientists say. Smokers are much more likely to experience depressive symptoms, and quitting the habit improves mental health.

Smoking is not only harmful to physical health, but is also associated with mental disorders, researchers from the Hebrew University in Jerusalem found out. The study was published in the journal PLOS ONE .

Smoking, including passive smoking, is one of the main risk factors for morbidity and mortality worldwide, the authors note. Almost 90% of smokers acquire this habit before adulthood, 98% before the age of 26.

Previous studies have shown that people with depression and other mental disorders are more likely to start smoking than mentally healthy people. In particular, many studies have noted that smokers have a much lower quality of life and more pronounced symptoms of anxiety and depression.

More recent data have shown that there may be an inverse relationship – smoking becomes a predisposing factor for mental problems, and quitting it is associated with a decrease in depressive symptoms.

Together with colleagues from Serbia, the authors of the work interviewed more than 2,000 students of Serbian universities.

As it turned out, smoking students were several times more likely to suffer from depression than their non-smoking peers.

In particular, at the University of Pristina, depression was observed in 14% of smoking students and only in 4% of non-smokers, and in the University of Belgrade – in 19% smokers and 11% non-smokers. Women were more likely to suffer from depressive symptoms.

In addition, regardless of economic or social status, students who smoke were also more likely to complain of depression and had lower mental health scores (energy, social functioning) than non-smokers.

“Our study confirms existing evidence that smoking and depression are closely linked,” says Prof. Hagai Levin. “It’s too early to say that smoking causes depression. But tobacco seems to have a negative effect on our mental health.”

The Israeli government is actively cracking down on smoking – as of 2020, cigarettes are banned from display in stores, warning labels on packs are increased to 65% of the pack size, and all tobacco products and e-cigarettes must be sold in the same packaging, without logos or display manufacturer’s brand.

Levin would like such measures to take into account the impact of smoking on mental health.

“I encourage universities to advocate for the health of their students by creating cigarette-free campuses where not only is smoking banned, but tobacco advertising is also banned,” he says. “Combined with policies to prevent, screen and treat mental illness, these steps will go a long way towards combating the harmful effects of smoking on our physical and mental health.”

Researchers suggest that the whole thing is the effect of nicotine on the activity of neurotransmitters.

In addition, other chemicals in cigarette smoke indirectly stimulate the release of dopamine associated with feelings of satisfaction, which ultimately leads to mood swings.

Students generally have more mental health problems than non-degree peers, researchers note. This is probably due to the stress caused by the strict academic requirements. The authors of the work suggest that depression can push them to smoke, and then, in turn, only aggravate their condition. The researchers hope that quitting smoking will allow students to improve their mental health, but this remains to be tested.

Previously, British geneticists drew attention to the fact that

smoking can provoke not only depression, but also schizophrenia.

Since the prevalence of smoking among people with depression and schizophrenia is generally higher than among the rest of the population, they decided to find out whether the diseases predispose a person to smoking or vice versa.

After analyzing the genomes of almost half a million Britons and comparing them with data on their diseases and lifestyle, they found that a genetic predisposition to depression is associated with an increased likelihood that a person will start smoking. However, no such association was found for schizophrenia. At the same time, smokers, even without a genetic predisposition, were more prone to depression and schizophrenia.

Geneticists have discovered another effect of smoking.

It turns out it causes depression and schizophrenia – Meduza

Simone Scarano / Unsplash

In developed countries, people with schizophrenia and clinical depression are twice as likely to smoke as among people in these countries as a whole. For a long time, scientists could not find an unambiguous explanation for this fact. Perhaps people with mental illness are more likely to smoke because of the increased stress they experience, or perhaps smoking, schizophrenia and depression are independently associated with some other, unknown cause, such as a genetic predisposition. A new study by British geneticists is trying to put an end to this dispute. Using the latest methods of analyzing genetic data, scientists have found that we are talking about a real causal relationship: it turns out that smoking – in addition to everything that is already known about it – also contributes to the development of depression and schizophrenia.

According to the World Health Organization (WHO), smoking is the number one preventable cause of disease and premature death in the world. In Russia, more than 300,000 people die from smoking-related diseases every year, while every third smoker (.pdf) in the country: 15% of women and half of men.

There are significantly more smokers among people with mental illness than among the general population. The life expectancy of such people is almost 20 years less, and most of this harm to health is associated with the consequences of smoking. The connection between depression, schizophrenia, and smoking was seen more than 30 years ago, but at first, nicotine addiction was considered only as an addiction – one of many, along with alcohol and substance use.

By the mid-1990s, the self-treatment hypothesis emerged, according to which the increased frequency of addictions (including smoking) among people with schizophrenia and depression is explained by their desire to stop their symptoms artificially. The self-medication hypothesis extended this understanding of the mechanism to any type of addiction, but in the case of smoking, it at least had a clear biochemical meaning: the action of nicotine on brain neurons causes the release of serotonin and dopamine neurotransmitters – the very ones whose production decreases with depression and is associated with negative symptoms schizophrenia. An increase in the level of these neurotransmitters after smoking a cigarette can cause a temporary “cure” effect in patients, which, as the hypothesis suggests, is the basis of their increased psychological dependence and explains the increased proportion of smokers among such people.

The weakness of this reasoning is that schizophrenia and depression are illnesses of a very complex nature. No one still knows how and why they develop. Therefore, even if the neurotransmitter explanation looks very logical, in fact it is not proof of causality – the same mechanisms for the release of serotonin can actually work in the opposite direction, for example, provoking pathological mechanisms that stimulate the development of diseases. Therefore, until the mechanisms of the diseases themselves become sufficiently understood – at least to the extent that the causes of other diseases associated with smoking (lung cancer, for example) are understood – the self-medication hypothesis will be doomed to remain only a hypothesis.

At least, this view of the prospects for the study of the relationship between smoking and mental illness was common until recently. However, the spread of new methods of DNA analysis in the last 10-15 years, the creation of large banks of biological materials and the emergence of new methods of statistical analysis in biology have given rise to the hope that the mysterious connection can be revealed even without a thorough understanding of the mechanisms of schizophrenia – it cannot be counted on in the near future. account for.

First of all, we are talking about a special type of research – genome-wide association analyses, or GWAS. They are carried out as follows: volunteers from different groups (sick and healthy, smokers and non-smokers) fill out detailed questionnaires, provide medical histories and other data, donate blood or saliva. DNA is extracted from the samples, it is read in the laboratory – usually not in its entirety, but only individual “letters” that differ from person to person. They are called polymorphisms, or SNPs.

Based on these data, scientists then examine associations—that is, the statistical relationship between individual SNPs of a person and, for example, his history of mental illness. Data collection is usually carried out by large consortia and even governments, while analysis is carried out by separate independent groups of researchers. Therefore, on the basis of the same biobank of data, it is possible to conduct many studies on different topics – in the study under discussion, for example, the same UK Biobank was used as in the study of homosexuality.

GWAS research is actually much more complex than it first appears, primarily because different genes can interact with each other. If we are talking about a complex trait, especially associated with the psyche, then hundreds of different SNPs can be statistically significantly associated with it, and what mechanism underlies this relationship is completely unclear without additional research. In addition, usually even all these hundreds of SNPs taken together do not explain all the occurrences of a trait: most of the genetic contribution is “smeared” over a long tail of thousands of different SNPs, each of which makes only a small contribution to the manifestation of a trait.

Today, studies of this type have been carried out for both schizophrenia and smoking. SNPs are known that are significantly associated with an increased incidence of the disease, and those that are more common in those who smoke. The main task of such work is to find those biochemical pathways, the work of which is disrupted during a disease or changes, contributing to a tendency to smoke. However, as it turned out, even without knowing the exact mechanism that underlies all these pathways, based on GWAS data, it is possible to find out what is the cause and what is the effect in this case. And to clarify where the association between mental illness and smoking comes from. This becomes possible thanks to the method of data analysis, which came to medicine and biology from the economy.

The analysis that biologists call Mendelian randomization and economists call instrumental variable analysis has only very recently been applied (.pdf) to GWAS data. It is based on a rather simple idea. If we have two signs – for example, blood cholesterol and cancer – and we do not know how they are related to each other and whether they are influenced by some “third causes”, then we can use our knowledge of external factors , which, according to independent data, exactly affect one of the potential causes.

For example, it is known exactly about cholesterol which mutations cause a strong decrease in its level in the blood. It is also known that these mutations spread in the population completely by chance: whether or not a person receives such a mutation from his parents depends on the random distribution of alleles according to Mendel’s laws (hence the name of the method), and not on his cholesterol level, diet or social status.

The essence of the method is to use the known dependence of the “mutation → cholesterol” type and the fact that these mutations are distributed randomly in the population, as a kind of analogue of a randomized clinical trial. If in such studies the participants in the experiment are divided into groups (those who receive the drug or placebo) by scientists, then here this happens by itself. Someone gets “good” mutations, someone “bad”, but this distribution does not depend on social status or any other factors, but happens by chance. And since we know exactly how such mutations affect a person, then in the end we get a randomized effect, in which the owners of certain genetic features are similar to the placebo or drug groups in conventional studies.

In our example, if a cholesterol-lowering mutation occurs significantly more often in people with cancer, then we can be sure that its low level really somehow causes an increase in the incidence of cancer, and not just due to it due to what for a third reason.

In the new study, this principle was applied in much the same way, with the difference that for schizophrenia, and for depression, and for the genetic propensity to smoke, there is no single mutation that explains the increase in risk entirely. Instead, the authors used a set of previously established SNPs that collectively are responsible for some known increase in the likelihood of becoming a smoker or having a mental illness.

Generally speaking, research on the topic with Mendelian randomization by GWAS has already been done (eg here). However, so far they have not been very convincing – at least for the authors of the new work. The novelty of the article under discussion, according to them, is that it succeeded in: 1) collecting the most modern set of SNPs associated with the onset of smoking; 2) to develop a “correct” way to assess the intensity of smoking and the extent of its impact on health – for example, for those who quit smoking, the time elapsed since the moment of quitting this habit was exponentially weighed.

The results of the study, as already mentioned at the very beginning, indeed confirm the negative impact of smoking on mental health: the risk of encountering schizophrenia in smokers is 2. 27 times higher than in non-smokers, and being diagnosed with clinical depression is 2 times higher .

Here, at the risk of complicating the picture even more, it should be noted that in addition to the “smoking → mental illness” relationship, the authors also studied the reverse causality: “mental illness → smoking”. And they really found this causality – however, this time only for depression. For schizophrenia, the data were statistically inconclusive.

In other words, it turned out that both explanations put forward by scientists at the dawn of studying the connection under discussion can indeed take place in different situations: both smoking increases the risk of mental illness, and the diseases themselves (at least depression) can exacerbate the tendency to smoke – although the latter effect is much weaker than the former.

Whether this is due to the compensation mechanism proposed by the self-treatment hypothesis or not, of course, it is impossible to say from such data.