Doctors are being urged to consider other treatments for depression and anxiety besides antidepressant drugs.
Australia has one of the highest rates of antidepressant use in the world, with more than one in 10 people using the drugs — double the rate from the year 2000.
A new report in the Medical Journal of Australia said while use of antidepressants was continuing to rise, there was growing evidence the drugs were not as effective as once thought.
Dr Christopher Davey, who authored the report with Dr Andrew Chanen, said the gap between responses to medication and placebos was narrowing.
“There are probably three main reasons [for the falling effectiveness of antidepressant medications],” he told 774 ABC Melbourne’s Jon Faine.
“Historically [there has] been a lot of negative trials that didn’t show that the antidepressants were more effective than placebo and they were buried and never published. Researchers have got hold of them now.
“Second, the trials that were conducted for antidepressants are generally conducted in patients with more severe and complex illness, where perhaps they are less effective.
“The third reason is that the placebo response seems to be getting much stronger, which is a really curious phenomenon.”
Drugs still more effective than placebo
Dr Davey said he was not suggesting people prescribed antidepressants should stop using them.
“I want to emphasise … that these studies show that, overall, the antidepressant medications are more effective than placebo,” he said.
“So I’d say to people keep going with the medication. But I would also say to them, where they feel like the medication by itself hasn’t been helpful, that they go back to their doctor and ask if they reviewed the medication.
“Also where they haven’t seen a therapist, [they could] see if they can see a therapist.”
Dr Davey said the community’s belief in the efficacy of antidepressant medications could have something to do with the strengthening placebo response.
“A big component of the placebo response is an expectation that you are going to get better [due] to medication,” he said.
“Despite what we’re finding, that overall the medications may be less effective than once thought, I guess in the community, perhaps, there is an expectation that the pills will help. So the placebo response is getting stronger.”
Dr Davey said antidepressant medications should be used in combination with other treatments such as psychotherapy.
Regular exercise and eating a healthy diet could also help people with depression, he added.