At this point, about one in 10 Americans is taking an antidepressant, according to CDC estimates . But a new study shows that nearly half of those prescriptions weren't given to treat depression.The study , published as a research letter in the most recent issue of JAMA, analyzed electronic records for 101,759 antidepressant prescriptions given out between 2006 and 2015 in Quebec, Canada. They found that only 55% of those were prescribed specifically to treat depression. Instead, the other 45% were most often prescribed for the treatment of anxiety disorders and off-label uses, including conditions like insomnia, pain, migraines, and ADHD.But that's not as worrying a figure as it might seem. Antidepressants work on complex systems that affect a lot of our biological processes. For instance, many of those drugs have been shown to be effective in treating some anxiety disorders. On top of that, sleep disturbances and pain are both commonly linked to depression. So some doctors believe antidepressants may even be better suited to treating those issues than drugs developed specifically to do so — or they may work where other more obvious treatments have failed."For insomnia use, most knowledgeable internists prescribe many of these medications because they are more effective and less problematic than drugs indicated for insomnia, such as Lunesta and Sonesta, which can have addiction counter-indications," Norman Sussman, MD, at NYU Langone Medical Center told CBS News . Similarly, there's an established history of using antidepressants to manage chronic pain — despite the fact that the drugs aren't indicated for that specific use.However, even if there's a precedent for using the drugs to treat these off-label conditions, that doesn't mean there's evidence for them. So, the study's authors are concerned that these prescriptions are based on word-of-mouth rather than science. Of course, that means more research needs to be done to really assess how effective antidepressants are in each of these cases. So for now, this is just a good reminder that because someone is on an antidepressant, it doesn't necessarily mean that person is suffering from depression.