It has become an epidemic. A little understood enemy is hiding among us. It’s silent; it’s invisible, mimics other common physical ailments and affects everyone.

Clinical depression often goes untreated. Only one in three depressed people get the help they need. The others either suffer in shame and silence or, even worse, take their own lives.

The Student Health Center offered free depression screening tests last week. The emotion of depression and the illness of depression tend to get confused. Although the symptoms are similar, the emotion always passes within hours or days — but the illness must be treated as a serious medical condition with therapy and medication.

There are two types of clinical depression. Situational depression is by definition depressive symptoms triggered by situational or environmental factors. This is what the Health Center was screening last week. College, an obvious life stressor, is assumed to be the primary trigger in this case.

Biological depressive symptoms are usually similar but triggered by a physical deficiency of serotonin levels in the brain, which is most often referred to as the “chemical imbalance.” Researchers have not been able to determine exactly why serotonin doesn’t maintain normal levels in some people.

The advertisements you see on television and hear on the radio about Zoloft or Paxil treat the illness, so hopefully you’ve already heard about the signs and symptoms.

Depression can be tough to diagnose because it often accompanies other medical, psychiatric and substance abuse disorders, so sometimes even health care professionals miss it.

Depressive illnesses sap energy, so the very nature of this condition can interfere with a person’s ability or desire to get help.

Those who have never experienced any kind of depression might perceive an undiagnosed individual as lazy, slow or apathetic. A common misconception is that a clinically depressed person can simply “snap out of it” or get over it on their own and they have no one but themselves to blame.

A lot of insurance companies do not recognize depression as a serious medical condition and thus will not provide adequate coverage for medication and therapy sessions. That’s why a large percentage of depressed people do not have access to the treatment they need.

The United States loses between $30 and $50 billion a year in worker productivity and direct medical costs related to depression. According to Dr. Kenneth Wells, a mental health researcher for the RAND Corporation, only 25 percent of depressed people are insured for mental health and receiving appropriate care. By comparison, he noted, if only 25 percent of cardiac patients were insured for that disease and receiving proper treatment, a national scandal would result.

Disorders of the brain are more difficult to diagnose than disorders of the body, but that doesn’t mean efforts shouldn’t be made, nor does it excuse insurance companies from providing appropriate coverage for patients who legitimately need it. The basic paradigm of Western health care is diagnose, treat and send away. That works well enough for most physical ailments, but mental illness requires a different approach and a shift in cultural attitude

Depression isn’t clearly visible like a broken bone, an abnormal mass on an X-ray or as obvious as a paraplegic in a wheel chair. Depression isn’t like pneumonia or a sinus infection that one round of antibiotics will quickly treat. Depression cannot always be easily spotted like a blind person using a white cane, or deaf person using sign language.

Those who have never experienced any type of depression have no idea just how debilitating the illness is. The overwhelming complexity of the human brain and the fact that no one has direct access to someone’s thoughts and emotions are what makes depression — or any mental health disorder — so dangerous, and the reason for the high suicide rate among people suffering from these untreated conditions.

Depression will either affect you or someone you know during your lifetime, and it’s important you know help is available. A person who is either diagnosed and experiencing a depressive episode or symptoms of depression desperately needs our compassion, patience and medical attention. For some, that may mean physically taking a friend or family member to the doctor. For others, that may mean making a long overdue appointment with a counselor or therapist.

It can’t always be cured, but it can be treated and managed as long as society, lawmakers and insurance companies understand the need and work together.