The researchers, Falk Leichsenring of the University of Giessen and Sven Rabung of the University Medical Center Hamburg-Eppendorf, both in Germany, reviewed only those studies in which the therapy had been frequent  more than once a week in many cases  and had lasted at least a year or, alternatively, had been 50 sessions long. Further, the studies had to have followed patients closely, using strict definitions of improvement.

The investigators examined studies that tracked patients with a variety of mental problems, among them severe depression, anorexia nervosa and borderline personality disorder, which is characterized by a fear of abandonment and dark squalls of despair and neediness.

Psychodynamic therapy, Dr. Leichsenring wrote in an e-mail message, “showed significant, large and stable treatment effects which even significantly increased between the end of treatment and follow-up assessment.”

The review found no correlation between patients’ improvement and the length of treatment. But improve they did, and psychiatrists said it was clear that patients with severe, chronic emotional problems benefited from the steady, frequent, close attention that psychoanalysts provide.

“If you define borderline personality broadly as an inability to regulate emotions, it characterizes a lot of people who show up in clinics, whether their given diagnosis is depression, pediatric bipolar or substance abuse,” said Dr. Andrew J. Gerber, a psychiatrist at Columbia. For some of those patients, Dr. Gerber said, “this paper suggests that you’ve got to get into longer-term therapy to make improvements last.”

Some psychoanalysts were more surprised by where the paper appeared than by its results: most review papers in major medical journals have hundreds of studies to draw on, or certainly far more than 23. The new review is encouraging, they said, but also a reminder of how much more study needs to be done.

Dr. Barbara L. Milrod, a professor of psychiatry at Weill Cornell Medical College, who like Dr. Gerber is a clinical practitioner of psychodynamic therapy, said further research was crucial as a matter of survival for a valuable treatment.

“Let’s be real,” Dr. Milrod said. “Major medical centers have been shutting down psychodynamic training programs because there isn’t an adequate evidence base.”