Chantix side effects

Varenicline (AKA Chantix) is a prescription-only smoking cessation medicine that has now been on the market for a couple of years. While studies have shown it to be safe and effective, post marketing surveillance (ultimately via reports by users) have raised concerns that some people may experience severe neuropsychiatric side effects as a result of taking the medicine. In particular, there has been a concern that that people with a psychiatric history (most of whom were excluded from the initial studies) may be at risk if neuropsychiatric symptoms such as depressed mood, agitation, lapses in concentration and suicidal thinking.

There have been relatively few studies of Chantix that included people with a mental illness, so that remains a concern. But last month a new study was published which examined side effects among Chantix users with and without a lifetime history of depression. The study, by Dr Jennifer McClure (Group Health Center for Health Studies, Seattle) and colleagues, compared the rates of side effects among people with (n=661), and people without a history of depression (516) who used Chantix to try to quit smoking while receiving phone and/or internet counseling. The study excluded people suffering from schizophrenia, bipolar disorder, and a few other illnesses. All participants received a telephone interview before starting treatment and 21 days and 3 months after their target quit date (i.e. approx 4 weeks and 13 week s after starting taking Chantix).

The first main finding was that, overall, ratings of symptoms such as depression or stress actually declined after the participants started taking Chantix (and tried to quit smoking), both for those with and without a history of depression. However, smokers with a history of depression felt more tense, irritable, depressed, and confused than those without a history of depression, 21 days after their target quit date (as they did at baseleine), and people with a history of depression who reported depressed symptoms were more likely to report severe depression than those without such a history at 21-day follow-up.

When examining actual change of mood, as compared with baseline, the majority of both groups mood improved after starting Chantix, but 10% of those with a history of depression had a significant worsening, as did 8% with no history of depression. Unfortunately this study was not able to compare these frequencies with people quitting smoking while taking placebo, but earlier placebo-controlled trials have not found a higher rate of mood worsening in Chantix users: quite the opposite.

One other thing worth noting is that both groups had very impressive quit rates, that were actually very slightly higher among those with a history of depression (45%) than those without: (42%) at 3 month follow-up.

So what does all this mean? The study authors interpreted the findings as suggesting that Chantix could be a particularly appealing treatment option for those smokers with a history of depression. Although such smokers are more likely to report common Chantix side effects and nicotine withdrawal symptoms, they had equally high quit rates without clear evidence of a worsening of mood.

So overall these results are somewhat reassuring, and suggest that perhaps we don’t need to be particularly cautious about Chantix use in those with a depression history. However, clinicians, patients and their families and colleagues should continue to monitor patients who are trying to quit smoking, and alert a clinician if a severe worsening of any symptoms appears to be occurring.

Here’s a link to a summary of the study:

Here are links to a couple of previous blog posts on Chantix and its side effects, including comments by many people who either did or did not experience side effects:

Note: I have done consulting and other paid work for Pfizer, the manufacturer of Chantix, as well as for the manufacturers of other smoking cessation products. See disclosure statement on my homepage at
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About the Author

MA, MAppSci, PhD

Dr. Jonathan Foulds is an expert in the field of tobacco addiction.