Patients with severe mental illnesses, such as schizophrenia, are 3 times more likely to smoke than the general population.1 In fact, as many as 60% of patients with schizophrenia are smokers.2 Although smoking is a modifiable risk factor, people with severe mental illnesses typically don’t seek smoking cessation services.1 Are those with schizophrenia genetically predisposed to smoking? Is the habit a form of self-medication? And lastly, how can mental health professionals encourage patients with schizophrenia to quit smoking?

Fast Facts: Smoking and Schizophrenia

Links between smoking and schizophrenia are many. In general, compared with those without mental illness, people with severe mental illnesses such as schizophrenia1,2:

  • begin smoking at an earlier age;
  • smoke more cigarettes per day;
  • smoke more intensely, drawing more nicotine per cigarette;
  • are more nicotine dependent;
  • are less likely to receive help quitting; and
  • are more likely to develop smoking-related illnesses.

The incidence of lung cancer among patients with schizophrenia is more than 4 times higher than in the general population of the United States, according to research.2 Additionally, smokers with schizophrenia were more likely to consume alcohol regularly and are less likely to watch their intake of salt and saturated fat, follow a high-fiber or low-calorie diet, or exercise regularly compared with nonsmokers who have schizophrenia.2

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Smoking, Genetics, and Schizophrenia

There is evidence of a genetic link between smoking and schizophrenia.2 In fact, heritability of smoking in schizophrenia is estimated to be as high as 65% compared with only 20% in the general population.2

Studies have shown that fetal exposure to nicotine during pregnancy increased the odds of schizophrenia in offspring.2 More specifically, a greater maternal serum cotinine level was associated with increased risk for schizophrenia later in life, meaning that heavy smoking may affect fetal brain development, making the brain more vulnerable to mental illness.2

Smoking intensity may play an important role in determining certain aspects of schizophrenia. Adolescents who smoked more than 10 cigarettes each day had a higher risk of developing psychosis compared with nonsmokers, according to a prospective study.2 Further, individuals who started smoking before age 13 had greater risk for psychosis later in life than those who became daily smokers after the age of 14.2

The reason patients with schizophrenia smoke so frequently and heavily compared with “healthy” patients may hinge on a shared genetic background between nicotine addiction and schizophrenia.2 A recent study sought to identify the genes and their corresponding pathways related to both smoking and schizophrenia. They compared genes that were associated with both conditions and found 52 shared genes.2 These results suggested that nicotine addiction and schizophrenia share some genetic liability, but more research is needed in this area.2

Is Smoking a Form of Self-Medication?

A long-believed perspective is that patients with schizophrenia smoke cigarettes more than the general population to “self-medicate” and alleviate impairments in processing speed, attention/vigilance, working memory, verbal learning, visual learning, reasoning, problem solving, and social cognition.2 Several clinical trials looked at the effects of nicotine intake on cognitive function in patients with schizophrenia, but the degree of nicotine dependence, the state of nicotine satiety, the state of nicotine withdrawal, and method of administration have varied widely between studies.2

There is some evidence that nicotine may acutely improve attention/vigilance, but the long-term benefits are unclear.2 In a more recent study, researchers used functional magnetic resonance imaging studies to examine the differences between smokers with schizophrenia and “healthy” smokers. These studies found2:

  • Smoking normalizes the right striatal and prefrontal cortical dysfunction in patients with schizophrenia.
  • Smoking induces dopamine release in cortical areas, particularly in the cingulate and prefrontal cortex, but also in the amygdala.
  • Heavy smoking of more than 25 cigarettes each day was related to excessive grey brain volume loss over 5 years in patients with schizophrenia.
  • Smokers with schizophrenia had increased activations in the bilateral ventromedial prefrontal cortex when shown provocative smoking images compared with smokers without schizophrenia.

Two studies conducted within large populations of European and Han Chinese patients with schizophrenia and healthy controls found that smoking was associated with significant cognitive impairment in both groups.2 Further, it has been reported that smoking more than doubled the risk for death by natural causes in patients with schizophrenia and bipolar disorder.2

Researchers posit that the high prevalence of smoking and reduced cessation rate among patients with schizophrenia may be attributed to the potentially higher pleasurable effects of cigarette consumption in this population coupled with indifference to its harmful effects.2

Providing and Promoting Smoking Cessation Services

“Guidance stresses that mental health services should become completely smoke free, and that all people who use mental health services should be given full access to smoking cessation interventions,” said Simon Gilbody, DPhil, a professor at the Department of Health Sciences at the University of York, York, United Kingdom.1

Evidence suggests that patients with schizophrenia can give up smoking, and that behavioral and pharmacological interventions can help.1 Researchers involved in the recent SCIMITAR+ trial developed a smoking cessation program specifically for those with severe mental illnesses. The program employed evidence-based techniques designed to alter behavior and introduce pharmacotherapy.1 Participants in the trial were divided into two groups: those who received usual care and those who had access to a bespoke smoking cessation program.

In usual care, people with severe mental illness were able to access free smoking cessation services provided by their primary care physicians or another local service. They also could call a free telephone helpline for advice. This group was advised to quit smoking, see their primary care physicians, and contact smoking cessation services.1

Participants allocated to the customized care group were offered a structured program delivered by trained mental health/smoking cessation professionals. They could request up to 12 (30-minute) face-to-face counseling sessions at home or in a clinic. To better serve people with severe mental illness, the program included several adaptations, including1:

  • making several assessments before setting a smoking quit date;
  • educating patients on a range of available pharmacological cessation aids, such as nicotine replacement and varenicline;
  • offering nicotine replacement before setting a quit date;
  • acknowledging the role of smoking in the context of a person’s mental illness;
  • providing home visits;
  • providing added face-to-face support after an unsuccessful quit attempt or relapse; and
  • communicating information to primary care physicians and psychiatrists regarding successful quit attempts to prompt a medication review.

Twice as many patients who received customized intervention quit smoking by the 6-month mark than those who received usual care: A successful quitter was defined as someone with a carbon monoxide measurement below 10 parts per million who also reported that they had not smoked in the past week.1 Additionally, those involved with the bespoke program were more likely to become engaged in their own treatment and more likely to receive pharmacotherapy.1 The trial also noted short-term improvements in self-reported physical health and, perhaps more importantly, no deterioration in mental health.1

Although the results of the SCIMITAR+ are encouraging, A. Eden Evins, MD, MPH, from the Center for Addiction Medicine and Schizophrenia Clinical and Research Programs of the Massachusetts General Hospital Department of Psychiatry and Harvard Medical School, Boston, Massachusetts, stresses that in addition to engagement, effective pharmacotherapy is critical for ensuring smoking cessation for patients with schizophrenia.3

There is evidence that varenicline is effective for smokers with schizophrenia or bipolar disorder, and bupropion used with or without nicotine replacement therapy has shown promise for patients with schizophrenia.1 In other studies, second-generation antipsychotics (clozapine and aripiprazole) were associated with lower tobacco smoking rates.2 In preclinical studies, clozapine and haloperidol have both suppressed nicotine seeking behaviors in rats.2

“It is not yet known how well smokers with serious mental illness would do if attempts to reduce or attempts to quit were consistently built on a foundation of pharmacological support, with the most effective pharmacotherapies offered proactively to all daily smokers,” said Dr. Evins. “We predict that this would lead to greater smoking cessation success and substantially reduced morbidity and mortality disparity for this population.”

Researchers recommend that clinicians ask every patient with severe mental illness about their willingness to quit smoking and refer potential participants to the most appropriate smoking cessation services in the community.1

“The results of the SCIMITAR+ trial will be helpful in informing clinical practice, since we have shown that quitting can be achieved for people who use mental health services just as it can for the general population of smokers,” said Gilbody.1

“The delivery of smoking cessation treatments should be a high priority in settings that provide care to patients with schizophrenia,” said Marina Sagud, MD, from the School of Medicine, University of Zagreb, Zagreb, Croatia. “In theory, beneficial effects of brain functioning exerted by nicotine might be obtained by substances mimicking those effects, which is an important area for future research.”2

References

1. Gilbody S, Peckham E, Bailey D, et al. Smoking cessation for people with severe mental illness (SCIMITAR+): a pragmatic randomised controlled trial. Lancet Psychiatry. 2019; 6(5):379-390.

2. Šagud M, Vuksan-Ćusa B, Jakšić N, Mihaljević-Peleš A, Rojnić Kuzman M, Pivac N. Smoking in schizophrenia: an updated review. Psychiatr Danub. 2018; 30(suppl 4):216-223.

3. Evins AE, Cather C, Daumit GL. Smoking cessation in people with serious mental illness [published online April 10, 2019]. Lancet Psychiatry. doi: 10.1016/S2215-0366(19)30139-7

This article originally appeared on Psychiatry Advisor