By all accounts, Hawthorne Heights guitarist Casey Calvert led a remarkable life. He toured the world with his compatriots, influenced many with his music, and touched people with his kind heart and seemingly boundless energy.

But, throughout his 26 years, there was one thing that wasn't as exceptional: a lifelong battle with depression.

More than 10 million Americans take some form of prescribed antidepressant medication, a number that has nearly tripled over the past 20 years and appears to show no signs of decreasing anytime soon.

According to data provided by the U.S. Centers for Disease Control and Prevention, of the more than 2.4 billion drugs prescribed in 2005 — the latest year for which data was available — more than 118 million were for antidepressants. And a study by IMS Health, a provider of market information to the pharmaceutical industry, reported that U.S. prescription-drug sales rose 8.3 percent to a staggering $274.9 billion last year, while the total number of prescriptions dispensed rose 4.6 percent. The majority of that bump was due to "six large, highly utilized classes [of medication,] including antidepressants, antipsychotics [and] anticonvulsants" that "comprised nearly one-fifth of U.S. pharmaceutical sales in 2006," the report states.

Calvert contributed to that number. At the time of his death, he was taking two of those classes of medication: citalopram, a selective serotonin reuptake inhibitor antidepressant, also known by the brand name Celexa; and clonazepam, a benzodiazepine-derived anticonvulsant, brand name Klonopin. However, by his bandmates' admission, the number of medications he was taking appeared to be in a near-constant state of flux.

"Casey wrestled with depression for as long as we knew him," drummer Eron Bucciarelli said in a statement. "He saw numerous doctors and took an ever-changing array of medicines to get better. He finally had his depression under control [before he died]."

That Calvert was taking more than one of these six classes of medication was not all that unusual. Dr. Carl Salzman, a professor of psychiatry at Harvard Medical School, told MTV News that both citalopram and clonazepam are "both very popular and both very commonly prescribed, often in conjunction with the other."

"You can't die by taking either of these drugs alone," Salzman said. "The problem comes when [patients] are taking them in mixtures or with alcohol — or if they are taken in higher levels. Then they can become dangerous."

And unfortunately, though interaction between two of the meds Calvert was prescribed — the clonazepam and Vicodin, which he was prescribed after undergoing a root canal — is rarely deadly, such incidents are on the rise. A report earlier this year by the CDC found that deaths from accidental drug interactions rose 68 percent between 1999 and 2004, making the problem the second-leading cause of accidental death in the U.S., behind only automobile accidents. The deaths of both R&B singer Gerald Levert and Anna Nicole Smith were attributed to accidental interactions between painkillers and antidepressants or anti-anxiety medications.

"Prescription drugs, especially prescription painkillers, are driving the prolonged increase [in fatal interactions]," the report said.

But considering how many people take antidepressants, the percentage of accidental-interaction deaths still remains relatively low — 20,000 people died from accidental interactions in 2004. And even lower still were the odds that an interaction between clonazepam and Vicodin would be the cause of death.

"Cases like Calvert's are so rare that they're almost nonexistent. It's so rare that you can't even put a number on it," Dr. John Mendelson, a pharmacologist at the California Pacific Medical Center Research Institute, told MTV News. "I mean, it's difficult to find someone these days who isn't taking some sort of medication, and deaths rarely occur. In older antidepressants, there was a large amount of cardiac toxicity, but with the meds we have today — Prozac or Effexor or Celexa — you can take 100 times the recommended amount and not overdose.

"In the case of this situation, it's just not a well-publicized problem, so to sit there and try to say, 'Well, the [Food and Drug Administration] should step in and pull this drug off the market,' or, 'The manufacturer should have a warning on the label,' that's just impossible," he continued. "So many people are taking these drugs, and sometimes the side effects are so minimal — one in 100,000 or something — that it's never going to be possible to list every possible side effect or interaction. You can't do it."

A spokesperson for the FDA told MTV News that drug-labeling information is owned and provided by the pharmaceutical companies, though that information must be approved by the FDA before the drug can be made available to the public. All antidepressant drugs come with a patient medication guide, to be given out at the pharmacy with the medicine.

Roche Pharmaceuticals, which manufactures clonazepam under the name of Klonopin in the U.S., provided MTV News with the labeling information that comes with the drug. In its 17 pages, opioids like Vicodin are not specifically mentioned, though the pamphlet does warn that patients "should be advised to inform their physicians if they are taking, or plan to take, any prescription or over-the-counter drugs, since there is a potential for interactions."

It's not known whether Calvert ever informed the doctor who prescribed him the Vicodin that he was also taking clonazepam. Even if he did, it's not certain that the combination of the two medications is what killed him (Mendelson speculated that his death was probably due to an arrhythmia). But with millions already taking prescription antidepressants and anti-anxietals — and millions more sure to be joining those ranks soon — should we be worried that we'll soon see more cases like Calvert's? And should we rethink the way we treat the very real disease of depression?

"I don't think you'll ever see an increase in cases like [Calvert's], and the issue of accidental interactions is really up to the patient to reveal to his or her doctor. Today we have relatively safe, nontoxic tools to treat depression, so the issue is, are we detecting more cases and offering treatment for more things, or is there more depression out there?" he continued. "I think, over time, young people have always struggled with post-adolescent angst, and a lot of that does represent clinical depression. ... I mean, 'Hamlet' is a story of depressed teenagers. The debate today is whether or not we'd give Hamlet Prozac, or whether we'd allow him to be a normal, depressed teenager."