When depression does not respond to antidepressant medication, replacing it with cognitive behavioral therapy (CBT) or adding CBT to treatment may be effective and last for several years, according to a trial in the U.K.

Three to five years after having up to 18 CBT sessions, trial participants were less depressed than those who didn't get the added behavioral therapy, suggesting a long-term benefit that makes CBT cost-effective, the authors conclude.

"Antidepressants are often prescribed for people with depression but we know that many people do not respond fully to such treatment," said lead author Nicola J. Wiles of the Center for Academic Mental Health at the University of Bristol.

"We previously found that giving (cognitive behavioral therapy) in addition to usual care that included antidepressant medication was effective in reducing depressive symptoms and improving quality of life over a period of 12 months in patients whose depression had not responded to treatment with antidepressants," Wiles said by email. "However, prior to this study, there was little evidence of effectiveness over the long-term."

Wiles' team followed up on a trial done in 73 general practices in the U.K. Between 2008 and 2010, 469 patients aged 18 to 75 years who had taken antidepressants for at least six weeks and still had substantial depressive symptoms were randomly assigned to either continue receiving usual care or to usual care with the addition of CBT.

Those in the CBT group attended 12 to 18 sessions with a therapist over about four to five months.

Three to five years later, the researchers followed up using general practitioner notes and questionnaires mailed to patients. The questionnaires were designed to gauge depression and also quality of life. Of the original group, 248 patients completed and returned the questionnaires.

Compared to those who only got usual care, the average depressive symptom score was about 5 points lower, on a scale of 0 to 63, for those who had received the CBT, even though those sessions had ended an average of 40 months earlier.

"People who are depressed often think about themselves and the world in a different and more negative way compared with how they thought before their illness," Wiles said. "Cognitive behavioural therapy, a type of talking therapy, is a way of helping people with depression change the way they think in order to improve how they feel and to change what they do."

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Patients learn skills to help them better manage their mood that they continue to use even after therapy sessions stop, she said.

In the trial, cognitive behavioral therapy cost an average of 343 British Pounds, or $489, annually per patient, the authors note in The Lancet Psychiatry.

"In our long-term follow-up, we found that CBT as an adjunct to usual care represented very good value for money for the health service," Wiles said.

There have been initiatives to increase access to such treatments in England and Australia, but they have focused on so-called low intensity interventions like computerized therapy packages and guided self-help, for which there is little evidence of long-term effectiveness, Wiles said.

The high intensity therapy delivered as part of general practice care in the U.K. trial reduced the significant burden to patients and healthcare systems caused by depression that does not respond to antidepressants, she said.

"It is very clear but often forgotten that depression is a long-term disease and most of the evidence that we have about what works comes from very short term studies," said Dr. Rudolf Uher of Dalhousie University in Halifax, Canada, who coauthored a commentary on the new results.

"This is the first demonstration that psychological treatment can be delivered efficiently in routine primary care," Uher told Reuters Health.

High-quality psychological treatment is often only available with out-of-pocket payment, and isn't standardized or promoted the way that pharmaceutical treatment is, he said.

"This shows that what would be considered a luxurious treatment actually pays for itself," he said.

But, he emphasized, even in this trial many patients were still at least somewhat depressed after treatment, and most were not "cured."