Cigarette Smoking May Increase Depressive Symptoms in Adolescents

Deborah Brauser

September 01, 2010

September 1, 2010 (Updated with comment September 2, 2010) — Smoking may increase symptoms of depression in adolescents, especially those who use cigarettes to feel better or to "self-medicate," according to a new observational substudy from the Canadian Nicotine Dependence in Teens (NDIT) trial.

"It's important to emphasize that depressive symptom scores were higher for the teenagers who reported emotional benefits from smoking after they began to smoke," lead study author Michael Chaiton, PhD, research associate at the Ontario Tobacco Research Unit, affiliated with the Dalla Lana School of Public Health at the University of Toronto, Ontario, Canada, told Medscape Medical News.

"Before smoking, all the adolescents [in the study] had roughly the same level of depression symptoms, but after they started smoking, [the smokers'] depression levels were much higher," added Dr. Chaiton.

He noted that this is "one of the few observational studies to examine the perceived emotional benefits of smoking" in adolescents and the first in this patient population to "demonstrate the long-term trend of perceived smoking-related psychobiological function on depressive symptoms over time."

The researchers write that these perceived benefits may simply come from the "alleviation of symptoms of [nicotine] withdrawal and craving resulting from abstinence.

"This repeated cycle of craving-satisfaction-craving-satisfaction that can occur many times a day for kids may lead to a higher level of depression over time and to worse outcomes," added Dr. Chaiton. Therefore, "self-medication scores may be useful in identifying a population who are susceptible to depression."

He also voiced concerns for clinicians "who may recommend holding off on smoking cessation" when dealing with patients with depression or other mental health disorders or addictions. "It's a dubious practice to rely on smoking as a self-medication tool."

The study was published online July 23 in Addictive Behaviors.

Smoking and Depression Links

Dr. Chaiton reported that his research team looked at the association between depression and smoking in adolescents in an earlier meta-analysis. "It's an area that's still up for debate, but we did find evidence that smoking may lead to depression and that depression may lead to smoking.

"So we wanted to go on and look at the potential reasons that differentiate adolescent smokers and find out why some may become depressed while others may not," he explained.

The NDIT trial was composed of 1293 adolescents from Montreal who were enrolled between the ages of 12 and 13 years. Follow-ups with these participants were conducted every 3 months for 5 years.

For this cohort study, the investigators examined data on 662 of the teenagers (61% female) who had smoked in the 3 months before any of the up to 20 self-report questionnaires given. Depression symptom scale, smoking status, and self-medicating questions were asked on each of the questionnaires.

Higher Self-Medication Equals Higher Depression

Results showed that the teens who reported higher self-medication scores also had significantly higher mean depressive symptom scores.

"The interaction between self-medication scores and the acceleration rate in depressive symptom scores was significant and negative, suggesting that participants with higher self-medication scores had decelerated rates of change in depression over time compared to participants with lower self-medication scores," explain the study authors.

To look also at the predictive ability of the self-medication scale, the researchers examined the full 1293 NDIT sample of adolescents. They found that after adjusting for confounders such as age and sex, "smokers with higher self-medication scores had a higher risk of onset of elevated depressive symptoms than never smokers" (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.7 – 3.3).

A "marginally higher risk" of developing increased symptoms of depression was also found for the smokers with low self-medication scores (HR, 1.3; 95% CI, 1.0 – 1.7). However, this association was no longer statistically significant after adjusting for confounders (HR, 1.1; 95% CI, 0.8 – 1.5).

"These results surprised us a little," said Dr. Chaiton. "We didn't realize that self-medication would necessarily make such a big difference. We were also surprised that the trajectories of depressive symptoms over time for those who smoked to self-medicate were quite different than nonsmokers."

He reported that the investigative team is continuing to follow up the study participants, who are all now in their 20s, to see what happens to their depressive symptoms as they reach adulthood.

A Step Forward for Science

"In helping science to take the next step forward, I thought [the researchers] did a nice job," Douglas Ziedonis, MD, MPH, professor and chair of the Department of Psychiatry at the University of Massachusetts Medical School and UMass Memorial Healthcare System in Worcester, told Medscape Medical News.

"It's an important study with a couple of key findings," added Dr. Ziedonis, who was not involved with this trial. "First, that smoking doesn't cure depression and is not effective in reducing depressive symptoms. It does alleviate withdrawal. And that sort of challenges some of the paradigms that many clinicians and patients have."

In addition, he noted that "whereas other studies haven't asked self-medication questions, this study actually had a tool to assess self-medication. Early identification of kids who think that smoking might help them might be an important screening tool for adolescent psychiatrists or pediatricians to use to help identify those at risk for smoking and for getting addicted to nicotine early in life.

"We could then give [these kids] the information that although it might seem [that smoking helps], it's only a short-term benefit. Then they get addicted, then they're in withdrawal, and they don't know the difference," he added. "Clinicians should also be aware that this might be a group that should get evidence-based approaches for helping them with their mood disorders."

When asked if he had any concerns with the study, Dr. Ziedonis said that he would point out that "there is a difference between depressive symptoms and mood disorders. And that concept was not as much described or talked about in the article. Also, potentially following these kids further is one possible way to make this study even stronger, to see if any disorders actually develop and not just symptoms."

The NDIT study was funded by the Canadian Cancer Society. The study authors and Dr. Ziedonis have disclosed no relevant financial relationships.

Addict Behav. Published online July 23, 2010.

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