The spirit of parity is twofold: cover both physical and mental disorders and pay for non-experimental, standard-of-care treatments.

Let’s take the first prong. Anorexia nervosa is indisputably a medical condition, not a trivial body image problem. It has one of the highest mortality rates among psychiatric disorders. Girls, women and, increasingly, males with anorexia nervosa typically develop defects in perception that could fairly be called delusional. Imagine a skeletal teen weighing 68 pounds who looks at herself the mirror only to see a fat girl staring back.

Now let’s turn to treatment. For severe cases, inpatient or residential treatment is often considered imperative, even life saving, and has been the standard of care for many years.

However, that standard falls short. Within the last decade, controlled treatment trials have revealed that their effectiveness is limited -- not zero, but limited. The relapse rate is very high, according to my colleague, Dr. Walter H. Kaye, who directs the eating disorders program at the University of California, San Diego, because patients are often unable to deal with the reduced structure in their life following discharge.

So, instead of spending months in a residential setting insulated from the outside world, state-of-the-art care for eating disorders is now taking place in the least restrictive setting possible. Such intensive daily treatment capitalizes on pragmatic strategies for coping with a patient’s disrupted appetite, anxiety, obsessive focus on food and unstable moods.

What does all this mean for the California ruling regarding private insurance companies? The dilemma is this: residential care, as some critics have alleged, may not be ideal, yet, as Dr. Kaye says, alternatives can be difficult to find. The most promising programs are usually associated with academic medical centers. Families depend on their local therapists or primary care doctors who may not know about these innovative treatments. And, if they are aware of the latest developments, there may not be professionals in the community who provide it.

It is impossible to compare medical and psychiatric modes of care in hope of making them 'equal.'

In the end, insurance should cover effective and appropriate treatment for anorexia nervosa, which may or may not be residential care, for a particular patient. Adding coverage for any medical illness according to category (e.g., residential care) is usually a bad idea. For one thing, the “victory” ruling implies that patients now have access to the Cadillac of care. Not only is this misleading -- residential is not necessarily the best modality -- it can make that particular intervention look more attractive simply because it had previously been denied. Second, since treatment often follows financing, patients may be preferentially steered toward residential care when less restrictive but new forms of intervention may be comparable and are probably better.

As far as parity is concerned, there are no obvious metrics for defining “doses” of treatment. Thus, it is impossible to compare medical and psychiatric modes of care in hope of making them “equal.” At best, we can hold insurers to covering a reasonable amount of current-practices treatment in accord with the same coverage and utilization limits as other non-mental health types of treatment under similar insurance coverage policies. State laws or court rulings should not require them to do more than that in offering fair and equitable coverage and should stop well short of dictating more narrowly defined modes of specific treatment or specific amounts and durations.

Sally Satel is a psychiatrist and resident scholar at AEI.