They analysed 23 medical studies involving more than 1 000 patients and found people with complex mental disorders who got long-term treatment fared far better.
"There is evidence that for patients with chronic mental disorders or personality disorders, short-term psychotherapy is not sufficient," said Dr Falk Leichsenring of the University of Giessen in Germany, who helped lead the study.
The researchers found patients with significant mental health issues who got therapy for at least a year were better off than 96% of the patients undergoing shorter-term treatment.
"Long-term psychodynamic psychotherapy showed significant, large and stable treatment effects, which even significantly increased between end of treatment and follow-up assessment," said Leichsenring, whose research appears in the Journal of the American Medical Association.
Long-term psychoanalysis 'effective, affordable'
Although it represents a classical model of psychotherapy, long-term psychoanalysis remains controversial because there is so little evidence showing its effectiveness, and insurance companies are loath to pay for treatments that lack hard data showing they work.
Not only is it effective, Leichsenring said in an e-mail, but "it also seems to be cost-effective."
Dr Jack Drescher, a psychiatrist who practices in New York, said the findings are consistent with what he has seen in his own practice. "Medications, whatever the condition, only take you so far," Drescher said. "My experience shows people benefit from longer-term treatment in which they are able to deepen the coping skills they develop in psychotherapy."
Dr Richard Glass, deputy editor of the journal, said in a commentary that the findings are somewhat limited by the quality and limitations of the studies the researchers reviewed. But he said they do offer rare evidence that this longer form of therapy works for certain patients who often do not benefit from short-term treatment.
"It is ironic and disturbing that this occurs at a time when provision of psychotherapy by psychiatrists in the United States is declining significantly," Glass wrote.
A study last month in the Archives of General Psychiatry found 29% of office-based visits to psychiatrists involved psychotherapy in 2004-5, down from 44% in 1996-97.
Glass said the trend appears to be "strongly related to financial incentives and other pressures to minimise costs. Is that what is really wanted for patients with disabling disorders that could respond to more intensive treatment?" he wrote. – (Reuters Health, October 2008)