Incidence of psychiatric disorders has increased in a shrinking population of smokers

The findings were published in Molecular Psychiatry.

The study revealed that as overall rates of smoking decreased, beginning in the 1960s, the proportion of smokers who are nicotine-dependent increased. The study also found that the likelihood of having a substance use disorder increased among all smokers with each decade, regardless of their dependence on nicotine. Nicotine-dependent smokers who began lighting up in the 1980s were also more likely than older smokers to have a psychiatric condition such as attention deficit hyperactivity disorder (ADHD), bipolar disorder, or antisocial personality disorder.

"Our study confirms that recent smokers, though a relatively smaller group than those who started smoking decades ago, are more vulnerable to psychiatric and substance use disorders," said lead author Ardesheer Talati, PhD, assistant professor of clinical neurobiology (in Psychiatry) at CUMC and NYSPI and a co-author of the study. "These findings suggest that today's adolescent and young adult smokers may benefit from mental health screening so that any related psychiatric or substance use problems can be identified and addressed early."

Smoking rates steadily increased during the first half of the 20th century. Beginning in the 1960s, growing recognition of the health risks associated with smoking led to a gradual decline in smoking rates, from nearly half of the US population in the 1950s to fewer than 20 percent today.

Researchers from Columbia University Medical Center (CUMC) and New York State Psychiatric Institute (NYSPI) speculated that as smoking became increasingly stigmatized, the relative few who began smoking in later decades may be more susceptible to psychiatric and substance use disorders.

"The association between smoking and psychiatric and substance use problems has been well documented," says Deborah Hasin, PhD, professor of epidemiology (in Psychiatry) at CUMC, director of the Substance Abuse Research Group at NYSPI, and a co-author of the study. "The current question is whether people who began smoking when it was less socially acceptable to do so were also somehow more likely to have mental health and substance use problems."

The researchers investigated this hypothesis among 25,000 people who participated in the National Epidemiological Survey of Alcohol and Related Conditions (NESARC), a large epidemiological survey funded by the National Institute of Alcohol Abuse and Alcoholism. The participants were divided into five birth groups: those who were born in the 1940s, 1950s, 1960s, 1970s, or 1980s.

"These findings also have implications for ongoing nationwide efforts to support smoking cessation efforts," notes Katherine Keyes, PhD, assistant professor of Epidemiology at Columbia's Mailman School of Public Health, and a co-author. "Given that mental health problems are also predictive of unsuccessful efforts to reduce or quit smoking, these findings suggest that cessation efforts that treat both withdrawal from nicotine and underlying mental health conditions are increasingly crucial."

The authors noted that additional studies are needed to determine if there is a causal relationship between biological or genetic factors and mental health or substance use problems in smokers.