As we reported recently, a significant portion of people on antidepressants aren’t suffering from depression at all — so why exactly are they taking the drug? You might be surprised why — and how often.

Millions of people are prescribed antidepressants every year even without an underlying depression issue, and it’s leading to a huge increase in sales for antidepressants — and that could be a bad idea, according to a JAMA Network Journals statement.

Doctors are prescribing antidepressants for a lot of strange reasons, including conditions like migraines and obsessive compulsive disorders — and sometimes even to prevent premature ejaculation.

The most common “off-label” use is for anxiety, which is often closely related to depression, but scientists are worried that two-thirds of all non-depression related are for off-label purposes, which means they haven’t been adequately tested to see if they’re effective.

That means people are spending gobs of money on a treatment that may not work at all, or worse may actually be harmful, the study warns.

The findings are based on 102,000 antidepressant prescriptions written by 158 physicians for 120,000 patients in Quebec between 2006 and 2015. Just 55 percent of those prescriptions were for depression.

“The findings indicate that the mere presence of an antidepressant prescription is a poor proxy for depression treatment, and they highlight the need to evaluate the evidence supporting off-label antidepressant use,” the authors said in the statement.

The statement adds: “During the study period, 101,759 antidepressant prescriptions (6 percent of all prescriptions) were written by 158 physicians for 19,734 patients. Only 55 percent of antidepressant prescriptions were indicated for depression. Physicians also prescribed antidepressants for anxiety disorders (18.5 percent), insomnia (10 percent), pain (6 percent) and panic disorders (4 percent). For 29 percent of all antidepressant prescriptions (66 percent of prescriptions not for depression), physicians prescribed a drug for an off-label indication, especially insomnia and pain. Physicians also prescribed antidepressants for several indications that were off-label for all antidepressants, including migraine, vasomotor symptoms of menopause, attention-deficit/hyperactivity disorder, and digestive system disorders.”