Because the symptoms of depression can be confused with other physical and mental illnesses, the diagnosis is often overlooked, and treatment thus delayed.

For instance, one study showed doctors frequently fail to recognize mood problems in cancer patients.

Researchers at University Hospital Cancer Center in Newark, N.J., looked at 400 patients ages 20 to 86 who were receiving cancer treatment.

They found 40 percent were suffering from depression. But 75 percent of the depressed patients received neither a diagnosis nor treatment.

Other research has shown that the rate of depression is at least twice as high in cancer patients as the general population.

Many people believe that suffering from a mental disorder like depression is a sign of weakness. As a result, they hide their symptoms from friends, family members, and even their doctors because they feel stigmatized.

Some depressed people also feel guilt because they can’t pull themselves out of the condition through their own will power.

But the truth is guilt and misperceptions about depression are often symptoms of the disorder.

Unfortunately, these kinds of attitudes delay treatment that can save lives. That’s because people with untreated depression have higher rates of mortality than those who receive treatment.