How Helpful Are Antidepressant Medications?

LESLEY STAHL: Irving Kirsch is the associate director of the Placebo Studies Program at Harvard Medical School. And he says that his research challenges the very effectiveness of antidepressants.

IRVING KIRSCH: The difference between the effect of a placebo and the effect of an antidepressant is minimal for most people.

LESLEY STAHL: So you're saying, if they took a sugar pill, they'd have the same effect.

IRVING KIRSCH: They have as almost as large an effect. And whatever difference there would be would be clinically insignificant.

LESLEY STAHL: But people are getting better taking antidepressants. I know them.

IRVING KIRSCH: Oh, yes.

LESLEY STAHL: We all know them.

IRVING KIRSCH: People get better when they take the drug, but it's not the chemical ingredients of the drug that are making them better. It's largely the placebo effect.

LESLEY STAHL: Irving Kirsch's specialty has been the study of the placebo effect, the taking of a dummy pill without any medication in it that creates an expectation of healing, that is so powerful, symptoms are actually alleviated.

IRVING KIRSCH: This is the placebo response—

LESLEY STAHL: Kirsch, who's been studying placebos for 36 years, says sugar pills can work miracles.

IRVING KIRSCH: Placebos are great for treating a number of disorders, irritable bowel syndromes, repetitive strain injuries, ulcers, Parkinson's disease.

LESLEY STAHL: Even traumatic knee pain. In this clinical trial, some patients with osteoarthritis underwent knee surgery. While others had their knees merely opened and then sewn right back up.

IRVING KIRSCH: And here's what happened. In terms of walking and climbing, the people who got the placebo actually did better—

LESLEY STAHL: Come on.

IRVING KIRSCH: —than the people who got the real surgery.

LESLEY STAHL: No.

IRVING KIRSCH: And that lasted for a year. At two years after surgery, there was no difference at all between the real surgery and the sham surgery.

LESLEY STAHL: Is it all in your head or—

IRVING KIRSCH: Well, it's not all in your head, because the placebos can also affect your body. So if you take a placebo tranquilizer, you're likely to have a lowering of blood pressure and pulse rate. Placebos can decrease pain. And we know that's not all in the mind also, because we can track that using neuroimaging in the brain as well.

LESLEY STAHL: He says the doctors who prescribe the pills become part of the placebo effect.

IRVING KIRSCH: The clinician who cares, who takes the time, who listens to you, who asks questions about your condition and pays attention to what you say, that's the kind of care that can help facilitate a placebo effect.

LESLEY STAHL: He says he got into researching the effect of antidepressants by accident.

IRVING KIRSCH: I was interested in evaluating the size of the placebo effect. I really didn't even care about the drug effect, because everybody, including me, knew it worked. I used to refer patients to get prescriptions. I didn't change the focus of my work onto looking at the drug effect, until I saw the data from our first analysis.

LESLEY STAHL: What he saw was that it almost didn't matter what kind of pill doctors gave patients.

IRVING KIRSCH: We even looked at drugs that are not considered antidepressants—tranquilizers, barbiturates. And do you know what? They had the same effect as the antidepressant.

LESLEY STAHL: Come on.

IRVING KIRSCH: Really.

LESLEY STAHL: Kirsch was so surprised by his initial findings, he decided to do a second study using data not only from the drug companies' clinical trials that had been published in medical journals. This time, he got data that weren't published but had been submitted to the FDA, which he got through the Freedom of Information Act.

IRVING KIRSCH: These are the studies that showed no benefit of the antidepressant over the placebo. What they did is they took the more successful studies, they published most of them. They took their unsuccessful studies, and they didn't publish them.

LESLEY STAHL: So when you did your study, you put all the trials together.

IRVING KIRSCH: That's right.

LESLEY STAHL: You're looking at patients who took the real drug and patients who took the placebo.

IRVING KIRSCH: Yes.

LESLEY STAHL: Did they get equally better, or did the ones who took the pills get even a little better?

IRVING KIRSCH: If they were mildly or moderately depressed, you don't see any real difference at all. The only place where you get a clinically meaningful difference is at these very extreme levels of depression.

LESLEY STAHL: Now, look, psychiatrists say the drug works.

IRVING KIRSCH: Right.

LESLEY STAHL: The drug companies and their scientists say the drug works. Maybe you're wrong.

IRVING KIRSCH: Maybe. I'd add to that, by the way patients, say the drugs worked.

LESLEY STAHL: Patients say the drug worked.

IRVING KIRSCH: And for the patients and the psychiatrists, it's clear why they would say the drug works. They take the drug, they get better. Our data show that as well.

LESLEY STAHL: You're just saying why they get better.

IRVING KIRSCH: That's right. And the reason they get better is not because of the chemicals in the drug. The difference between drug and placebo is very, very small. And in half the studies, nonexistent.

LESLEY STAHL: Dr. Walter Brown is a clinical professor of psychiatry at Brown University's medical school. He has co-authored two studies that largely corroborate Kirsch's findings.

WALTER BROWN: The number of antidepressant prescriptions over the last decade has increased. And most troublesome, the biggest increase is in the mildly depressed, who are the ones who are least likely to benefit from them.

LESLEY STAHL: He says they are getting virtually no benefit from the chemical in the pill. Like most experts, he says these drugs do work for the severely depressed. It's so modest that in great Britain, the National Health Service decided to dramatically revamp the way these drugs are prescribed. It did so after commissioning its own review of clinical trials.

TIM KENDALL: We came to the conclusion that for mild to moderate depression, these drugs probably weren't worth having.

LESLEY STAHL: At all.

TIM KENDALL: Not really.

LESLEY STAHL: Dr. Tim Kendall, a practicing psychiatrist and co-director of the commission that did the review says that, like Irving Kirsch, they were surprised by what they found in the drug companies' unpublished data.

TIM KENDALL: With the published evidence, it significantly over-estimated the effectiveness of these drugs, and it underestimated the side effects.

LESLEY STAHL: Because of the review, new public health guidelines were issued. Now, drugs are given only to the severely depressed as the first line of treatment.

MAN: Sure, yeah.

LESLEY STAHL: For those with mild to moderate depression, the British government is spending nearly half a billion dollars training an army of talk therapists.

WOMAN: If you want to go a little faster, you can.

LESLEY STAHL: Physical exercise is another treatment prescribed for the mildly depressed.

TIM KENDALL: By the end of 10 weeks, you get just as good a change in their depression scores as you do at the end of 10 or 12 weeks with an antidepressant.