For many years, some people with anorexia nervosa and other eating disorders who remained ill despite repeated treatments were described as having a “severe and enduring eating disorder.” The term was intended to identify people with complex and persistent illness. But it also carried a risk: The word enduring can easily be interpreted as permanent.

That matters. If clinicians, patients, or families begin to believe that an eating disorder is unlikely to improve simply because it has lasted many years, therapeutic expectations may gradually shift from recovery toward resignation.

A recent systematic review published in the Journal of Eating Disorders challenges this assumption. The review examined recent studies of adults with severe and longstanding eating disorders and found an important message: The duration of an eating disorder, by itself, does not reliably predict poor treatment outcome.

From “enduring” to “longstanding”

One of the first issues raised by the review is terminology. There is no universally accepted definition of “severe and enduring anorexia nervosa.” Different studies have used arbitrary illness-duration thresholds of three, five, or seven years. Some definitions have also included previous unsuccessful treatments, low weight, or persistent psychopathology. More importantly, people with lived experience have questioned whether the term enduring unintentionally suggests irreversibility.

For this reason, the authors suggest using the expression “longstanding and severe eating disorders” to acknowledge persistence and severity without implying treatment futility, reflecting a broader shift in clinical thinking.

What seems to matter more than illness duration?

Across the studies reviewed, people with longstanding eating disorders were able to make meaningful improvements in weight, eating-disorder psychopathology, general psychological symptoms, functioning, and quality of life. Importantly, illness duration was not a consistent predictor of treatment response.

A more relevant factor was whether patients achieved and maintained a healthier weight, particularly by the time they left intensive treatment. Across several studies of anorexia nervosa, a healthy discharge body mass index (BMI) was more consistently linked to better follow-up outcomes than the duration of illness. This has important clinical implications.

A person who has had anorexia nervosa for 10 or 15 years should not automatically be considered less capable of recovery than someone who has been ill for two or three years. The more useful question may be: “Has this person received a sufficiently intensive, coherent, and continuous treatment?”

Intensive and integrated treatment appears promising

The clearest positive signal in the review came from intensive, integrated treatment pathways. Although the evidence is still largely observational rather than based on randomized controlled trials, the most promising programs shared several features:

substantial or full weight restoration
specialist psychological treatment
multidisciplinary care
continuity between inpatient, day-patient, and outpatient treatment

This continuity may be especially important. Several inpatient studies showed substantial improvement during admission, followed by some deterioration after discharge. In other words, helping a patient improve during hospitalization is only part of the challenge. Maintaining that improvement after discharge is equally important.

What the intensive CBT-E studies found

Some of the strongest observational findings in the review came from studies of intensive enhanced cognitive behavior therapy (CBT-E).

In the largest Italian cohort, involving more than 400 adults with anorexia nervosa, more than 80 percent reached a BMI of at least 18.5 kg/m² at the end of intensive treatment, and more than 60 percent met criteria for a full response. More than half maintained full response at follow-up.

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A U.K. study comparing different inpatient pathways also reported better long-term outcomes and fewer readmissions among patients receiving an integrated CBT-E pathway than among those receiving less continuous forms of care.

These findings are encouraging, but they should be interpreted cautiously. Because the studies were not randomized, differences in patient selection, treatment preferences, disease severity, or service organization may have influenced the results. Still, the overall pattern is clinically important: Longstanding illness did not prevent substantial improvement.

Outpatient treatment alone may not always be enough

The review also found more limited results for standard outpatient treatment in people with severe and longstanding anorexia nervosa.

In one large U.K. study, patients improved modestly over 12 months, but more than 80 percent of those in the longstanding group eventually required escalation to day or inpatient treatment. This raises an important question: Can remaining for too long in an insufficiently intensive treatment contribute to continued illness?

For some patients, the issue may not be “treatment resistance” but, rather, that the “level of treatment has not matched the severity of the problem.”

Recovery and quality of life are not competing goals

Another important message is that weight restoration and quality of life should not be viewed as opposing treatment goals. Malnutrition can affect concentration, emotional regulation, social functioning, physical health, and the ability to engage in psychological treatment. For this reason, nutritional rehabilitation is not merely about changing a number on the scale. It can create the conditions in which broader psychological and social recovery becomes more possible.

Avoiding therapeutic pessimism

The evidence isn’t perfect, with most studies on women with anorexia nervosa, limited randomized trials, short follow-ups, and underrepresented diagnoses. However, the review argues that long illness duration doesn’t mean irreversibility. A longstanding eating disorder is undoubtedly more complex and needs intensive treatment, but years of illness alone shouldn’t dismiss recovery-focused care.

Perhaps the most important shift is from asking: “How long has this person been ill?” to asking: “What treatment has this person received, at what intensity, and with what continuity?”

That change may help replace therapeutic pessimism with a more evidence-informed and recovery-oriented perspective.