Smoking Teenagers Make Depressed Adults

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Main Category: Smoking / Quit Smoking
Also Included In: Pediatrics / Children's Health;  Anxiety / Stress;  Depression
Article Date: 29 Jan 2009 - 10:00 PDT

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A groundbreaking new study by researchers in the US suggests that teenagers who smoke could be setting themselves up to become depressed adults.

Published pre-press as an early on line issue last month in the journal Neuropsychopharmacology, the research was the work of Florida State University Psychology Professor Carlos A Bolaños-Guzmán and colleagues.

In their background information Bolaños and colleagues said research has already established a strong link between tobacco consumption and mood disorders, and while some might say smokers use tobacco to manage their moods, there is also evidence that tobacco consumption induces negative mood.

For the study, Bolaños and colleagues used adolescent rats (their neurobiology is similar to that of humans) and showed that giving them nicotine induced a depression-like state that left them less able to feel pleasure and more sensitive to stress in adulthood. The researchers suggested the same might be true of humans.

As Bolaños explained, the finding is unique because:

"It is the first one to show that nicotine exposure early in life can have long-term neurobiological consequences evidenced in mood disorders."

He also said their research showed that even brief exposure to nicotine raised the risk of mood disorders later in life.

For the study, they injected adolescent rats twice a day with various doses of nicotine or a saline solution (the controls) for 15 days. At various times during and then after exposure finished the rats also underwent tests that examined their responses to stressful circumstances and the offer of rewards. Separate groups of adult rats received a mid-range dose of nicotine to enable the researchers to rule out age-related effects.

The results showed that:

• Nicotine exposure during adolescence, but not adulthood, led to a depression-like state characterised by lower sensitivity to natural reward (sucrose) and enhanced sensitivity to situations that raised anxiety and stress in later life.


• Behavioural characteristics of depression can emerge 1 week after stopping nicotine exposure.


• A single day of nicotine exposure during adolescence is enough to trigger a depression-like state in adulthood.


• The depression behaviours went back to normal when the rats were given either nicotine or antidepressants (such as fluoxetine or bupropion) in adulthood.

The adult rats that had not been exposed to nicotine as teenagers did not show the depression-like symptoms, although they underwent tests in parallel with their teen-nicotine exposed counterparts.

Behaviours characteristic of depression and anxiety included repetitive grooming, less consumption of rewards like the sugary drinks they were offered, and "freezing" in stressful situations instead of trying to escape them.

Bolaños and colleagues concluded that:

"These data suggest that adolescent exposure to nicotine results in a negative emotional state rendering the organism significantly more vulnerable to the adverse effects of stress."

"Within this context, our findings, together with others indicating that nicotine exposure during adolescence enhances risk for addiction later in life, could serve as a potential model of comorbidity," they added.

Talking about the research to the press, Bolaños said that:

"Some of the animals in our study were exposed to nicotine once and never saw the drug again," but then it was "surprising to us to discover that a single day of nicotine exposure could potentially have such long-term negative consequences."

Speculating on the mechanisms that might underlie these findings, Bolaños said toxic effects in the brain could be responsible: effects which alter the way that neurotransmitter circuits behave later in life. Perhaps these mechanisms are sensitive at particular stages of development, such as during the teenage years. The researchers said this should be the focus of new studies.

In the meantime, the message to young people is:

"Don't smoke and don't even try it," said Bolaños. They need to be made aware of the long term risks they are taking, even from having the occasional cigarette.

The research was paid for by grants from the state of Florida's James and Esther King Biomedical Research Program and the National Institute on Drug Abuse. Funds also came from a McKnight Fellowship from the Florida Education Fund and Neuroscience Fellowships from Florida State University.

"Nicotine Exposure During Adolescence Induces a Depression-Like State in Adulthood."
Sergio D Iñiguez, Brandon L Warren, Eric M Parise, Lyonna F Alcantara, Brittney Schuh, Melissa L Maffeo, Zarko Manojlovic and Carlos A Bolaños -Guzmán.
Neuropsychopharmacology advance online publication 17 December 2008.
doi: 10.1038/npp.2008.220

Click here for Abstract.

Sources: Journal Abstract, Florida State University.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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