Varenicline, the operative drug in anti-smoking medications — like Chantix — approved by the U.S. Food and Drug Administration (FDA), has been linked to depression and suicide in a new study of about 13,000 people in New Zealand. Amid lawsuits from varenicline victims and studies that show an increased risk of suicide from the drug, the FDA still refuses to pull the medication from shelves.

The study, which was commissioned by New Zealand's government under the country's Official Information Act, found that of about 13,000 people aged 14 and older, 250 had sleep disorders, 154 were diagnosed with depression, and 80 suffered from anxiety in connection with varenicline. But in probably the most staggering statistic, six people committed suicide, four of whom officials potentially link to the use of varenicline.

"Suddenly on Champix (which is what the medication is called overseas) I was sad all the time, I cried over absolutely nothing," said Michelle Munro, who began taking varenicline to stop smoking. "I think it was maybe three or four days into it when my flatmates said, 'Oh my gosh, can you just have a cigarette, you are miserable - we haven't seen you smile or laugh in days and that's so unlike you.'"

Munro told 3News in New Zealand that she cried in bed a lot of nights and began sleepwalking. Her roommates began placing furniture in front of the door to make sure she didn't wander off in the middle of the night.

The stories of people like Munro, who took the drug in hopes of making healthier choices and ended up with a strange pattern of behavior, are more prevalent than they should be. But, when asked what they would do about it, New Zealand government officials answered similarly to the FDA: they would continue to fund the drug because its benefits outweigh its risks.

In the U.S., the FDA has issued fairly strong warnings about Chantix. But the agency has left the decision as to whether a patient should be prescribed the drug in the hands of medical professionals. In 2011, the FDA warned about Chantix and its risks after the agency conducted two studies of neuropsychiatric adverse events in Chantix users. However, the agency said that it would continue to evaluate the drug in an ongoing clinical trial with findings expected in 2017. Until then, it seems as though health professionals may freely prescribe Chantix to patients who want to quit smoking.

"FDA is continuing to evaluate the risk of neuropsychiatric events with Chantix. The drug manufacturer is conducting a large safety clinical trial of Chantix to assess neuropsychiatric adverse events, and results from this study are expected in 2017.

Some patients have experienced changes in behavior, hostility, agitation, depressed mood, and suicidal thoughts or actions while using Chantix to help them quit smoking. Some patients had these symptoms soon after they began taking Chantix, and others developed them after several weeks of treatment, or after stopping Chantix. Before taking Chantix, patients should inform their healthcare professional if they have ever had depression or other mental health problems."

In 2012, the FDA did a podcast concerning a clinical trial that found a link between Chantix and the risk of cardiovascular problems. But once again, the agency left the decision in the hands of health care professionals, saying "Smoking is an independent and major risk factor for cardiovascular disease, and Chantix is effective in helping patients quit smoking. The health benefits of quitting smoking are immediate and substantial. Weigh the risks of Chantix against the benefits of its use."

Still, there has been no real action on the part of the FDA. The agency seems to place a great deal of the decision making surrounding varenicline in the hands of the health care professionals who prescribe it.

And, as if all of that wasn't enough, Chantix is also the defendant in a class action lawsuit from users of the drug who say that its side effects have had a severe negative impact on their lives, whether it be depression or suicide. Just last week, Legal-Bay LLC, a lawsuit settlement funding company, said that it will offer plaintiffs in the case with pre-settlement funding. The company, which is also offering funding to plaintiffs in a suit against NuvaRing, expressed its commitment to assisting the "victims of Chantix."