Younger Smokers More Likely to Suffer Psychiatric Comorbidities

Liam Davenport

February 08, 2016

Younger smokers are more likely to be dependent on nicotine and have psychiatric and substance use disorders than their older counterparts, new epidemiologic evidence shows.

Data on more than 25,000 individuals indicated that, although overall rates of smoking have decreased across the generations, rates of nicotine dependency have more than doubled. Furthermore, the link between smoking and psychiatric disorders has strengthened.

"The findings extend previous work showing that as smoking becomes less normative, psychiatric vulnerability among smokers increases," the investigators, led by Ardesheer Talati, PhD, assistant professor of clinical neurobiology/psychiatry at Columbia University Medical Center, in New York City, write.

"Although the current work does not address how this vulnerability is increasing, the increases cannot be accounted for solely by demographic shifts across time. The more recently born smokers thus represent a clinically high-risk cohort, and may benefit from earlier screenings for mental-health outcomes, which could in turn help optimize treatment," they add.

The study was published online January 26 in Molecular Psychiatry.

Hidden Cohort

The investigators examined data on 25,412 individuals enrolled in the National Epidemiologic Survey of Alcohol and Related Conditions. All participants had completed the Alcohol Use Disorder and Associated Disabilities Interview Schedule–DSM-IV Version.

The participants were divided into five birth cohorts by decade ― 1940s, 1950s, 1960s, 1970s, and 1980s; and three smoking cohorts ― nonsmokers, never-dependent smokers, and ever-dependent smokers.

The results indicated that although rates of smoking decreased across the five birth cohorts, the proportion of smokers with smoking dependence increased, from 30.8% of smokers born in the 1940s to 70.4% of those born in the 1980s (linear trend, P < .0001). These patterns remained after adjusting for sex, race, income, and education.

After adjusting for concurrent demographic and socioeconomic changes, the researchers found that associations between smoking and drug and alcohol use disorders, attention-deficit/hyperactivity disorder (ADHD), bipolar disorder, and antisocial personality disorder all increased across the birth cohorts.

For drug and alcohol use disorders, the increase in the association with smoking was seen in smokers with and without a history of nicotine dependence. However, for ADHD, bipolar disorder, and antisocial personality disorder, the increase was restricted to smokers with nicotine dependence.

Interestingly, the observed association between major depression and nicotine dependence did not vary across birth cohorts. The results were similar in non-Hispanic white, non-Hispanic black, and Hispanic subgroups.

Discussing the findings with Medscape Medical News, Dr Talati pointed out that smokers at higher risk for psychiatric disorders were previously hidden within the wider smoking cohort.

"The group of vulnerable people has always existed, but what we are saying, perhaps, is that many decades earlier, the vulnerable people were not isolated within smoker groups the way they are now or to the extent they are now," he said.

"Fifty years ago, you still had people who were at risk for all these disorders, but because smoking was more prevalent, smoking itself was not so marginalized, and so the distribution of smoking and the distribution of all these other risk traits were not as concentrated in one direction or the other. In more recent times, smoking itself has become less normative, and the concentration of all these factors might be getting more concentrated," he added.

The researchers suggest that differentiating between people who smoke only periodically and those who are more chronically dependent may help in identifying patterns of psychopathology and in prioritizing those at greatest risk.

Two-Way Street

Dr Talati explained that in terms of identifying more vulnerable smokers, it is, however, "a two-way street."

"We make clear in the article that we're not saying either that smoking causes the mental disorders or the other problems or, conversely, that the other problems cause smoking, although in some individuals, it may be in one direction or another.

"What it seems to be more is a marker. Let's say you have two people in a room and one is a 55-year-old and he or she is a smoker, and you have an 18-year-old who's a smoker. For the 18-year- old, you might be more inclined to do a more substantial screen...because that's also the age where you can intervene and have more of an effect.

"With the 55-year-old, you're less likely to have an effect, but, more importantly, if they've been smoking since they were, let's say, in their teens, they may be at higher risk for things like lung cancer or heart disease, but they may not necessarily be at higher risk for psychopathology," Dr Talati added.

He also noted that for some individuals with attentional disorders, the case for quitting smoking is not clear-cut.

"There are studies showing that if you smoke, you actually have better outcomes, and the reason is that the nicotine serves as a sort of self-medication or calming agent that helps them to function better," he explained.

"It doesn't necessarily mean that for anyone who smokes and has mental disorders, the goal [is] to get them to stop smoking and, in fact, one could make the case in some cases that smoking does more good than negative."

Dr Talati will next examine the biological basis of psychiatric comorbidity in smokers. He intends to investigate the genes involved in the specifics of nicotine dependence, as well as those more generally related to risk and reward. It is hoped that this will add further evidence to help determine whether smokers are changing not just behaviorally but also biologically.

Another area ripe for research is that of electronic cigarettes. Dr Talati said: "Because the whole paper is predicated on societal changes and societal trends in smoking and the correlates of that, we can't make any assumptions about what will be happening with these others forms of smoking.

"For example, with e-cigarettes, we see a completely different pattern, because someone who smokes an electronic cigarette may be very different from someone who smokes regular cigarettes. We also don't have as much longitudinal data on that."

The investigators are supported by grants from the National Institute of Drug Abuse, the National Institute on Alcohol Abuse and Alcoholism, and Young Investigator NARSAD (National Association for Research on Schizophrenia and Depression) grants from the Brain and Behavior Research Foundation.

Mol Psychiatry. Published online January 26, 2016. Abstract

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