WASHINGTON – Up to 25 percent of people whom psychiatrists would currently diagnose as depressed may only be reacting normally to stressful events such as divorces or losing a job – and antidepressant treatment may be inappropriate, according to a new analysis.

The finding on how standard diagnostic criteria are used could have far-reaching consequences for the diagnosis of depression, the growing use of symptom checklists in identifying people who might be depressed, and the $12 billion a year U.S. market for antidepressant drugs.

Patients are currently diagnosed on the basis of a constellation of symptoms that include sadness, fatigue, insomnia and suicidal thoughts. The diagnostic manual used by psychiatrists says that anyone who suffers from at least five such symptoms for as little as two weeks may be clinically depressed.

Only in the case of someone grieving over the death of a loved one is it normal for symptoms to last as long as two months, the manual says.

The new study, however, found that extended periods of depressionlike symptoms are common in people who have been through other life stresses such as divorce or a natural disaster and don’t necessarily constitute illness.

The study also suggested that drug treatment may often be unnecessary for people who are going through painful – but normal – responses to life’s stresses. Supportive therapy on the other hand, might be useful, and might keep a person from going on to develop full-blown depression.

The researchers, who included Michael First of Columbia University, the editor of the authoritative diagnostic manual, based their findings on a national survey of 8,098 people.

They found that people who had been through a variety of stressful events frequently had prolonged periods when they reported many symptoms of depression.

Only a fraction, however, had severe symptoms that deserved to be classified as clinical depression, the researchers said.

About one in six Americans are currently estimated to suffer depression at some point in their lives. Under the more limited criteria the researchers urged, that number would be 25 percent lower.

But First warned that people who are in pain after a divorce or other stressful event should not conclude that they simply ought to “buck up.” They should seek the counsel of clinicians who would take the time to explore what caused the symptoms and whether they need treatment.