Depression is one of the most common forms of mental illness, not least because it often comes back. At least half of those who are diagnosed with depression once will have one or more bouts with the disease over the course of a lifetime. And about 80 percent of those who experience two episodes of depression are likely to have a recurrence. According to one study, a second episode of depression usually occurs within five years of the first. Those with a history of depression will have, on average, five to nine separate episodes in their lifetime.

Knowing that, those with depression should consider their disease a chronic condition and act accordingly, according to the University of Michigan Depression Center: “Scientific evidence encourages us to view depression as a condition requiring care over a lifetime — not an episodic illness. This changes the focus from getting well to staying well.”

It’s not known why depression tends to return, or how to predict who will suffer a relapse and who won’t. However, physicians are beginning to understand what may trigger a recurrence, and how to reduce the risk of it happening.

[See: Am I Just Sad — or Actually Depressed?]

Common Relapse Triggers

In essence, the same life events that can trigger a first episode of depression are possible factors for a future event, says Dr. Sue Varma, a psychiatrist and clinical assistant professor at NYU Langone Medical Center. These include job loss, divorce, a death in the family or other traumatic losses. “Even some major positive changes that cause disturbances and changes in our role and identity can be a risk,” she says. “For women, 10 to 15 percent develop postpartum depression, and 4 percent of dads get postpartum, too. It can even be a job promotion where we don’t feel adequately prepared, causing undue stress.”

A family history of depression or having another psychiatric illness also are associated with relapse, she says, as are certain recurring negative emotions and social isolation. “High neuroticism and poor social support are correlated with relapse, but we don’t know if they cause it,” she says.

A physical illness or injury may also trigger a relapse, says Dr. Frederick K. Goodwin, clinical professor of psychiatry at George Washington University. “You get ill or you injure your foot and then you can’t be active, which is our definition of feeling well and not being depressed,” he says.

The most common risk factor for a relapse, however, is discontinuing treatment, the University of Michigan Depression Center reports. “Frequently, patients whose depressive episodes are successfully treated with medication and/or psychotherapy begin to feel better. Thinking they are ‘cured,’ they stop treatment, failing to refill their prescriptions, attend therapy sessions or follow through on their self-care program. In time, their depression returns.”

“It takes a while for recovery to settle in,” says Goodwin. “Patients can get over their depressive feelings, but depressive habits persist. Those habits have to be actively broken into and addressed. [Recovery] won’t necessarily continue on its own momentum.”

[See: Coping With Depression At Work.]

Relapse May Be Severe

Each subsequent episode of depression tends to be worse than previous episodes, according to the University of Michigan. Successive episodes may have a cumulative effect on the person’s sense of self-worth, Varma says. And they may require more fervent treatment. “Frequently, the previous medication may be necessary, but this time at a higher dose,” Varma says. “You are then trying to play catch up.”

Prevention, therefore, is the key. And that comes back to thinking of depression as a chronic disease, requiring chronic attention. Patients should continue to take their medications as prescribed, and seek regular guidance from their mental health provider to monitor the medication’s effectiveness. If patients are considering going off their meds for any reason — say, unpleasant side effects — they should never go “cold turkey,” as abruptly stopping the meds can cause significant health problems. Consult with the doctor first to come up with a safe plan to taper off medications gradually.

It may be wise to continue psychotherapy even after the depression is under control. That is more problematic, as insurance often doesn’t cover more than a limited number of sessions. However, at the first sign that symptoms are returning, revisiting the therapist is probably a good idea.

Being alert to those symptoms is critical, Goodwin says, as is planning for addressing them. If you can’t exercise in your normal fashion because of an illness, find another way. “Don’t let the fact that you can’t run bring you down,” he advises. And stay connected to others. “You have to keep reaching out and asking for feedback that lets you know that people do in fact care about you,” he says.

[See: The Many Ways Exercise Fights Depression.]

The bottom line is to treat depression as a lifelong illness, not unlike asthma or diabetes. “That means continuing to ‘work’ your treatment plan on good days as well as bad,” the University of Michigan suggests, “so that you are equipped to cope with the unavoidable stressors that can ignite a recurrence of depression.”

More from U.S. News

Could Your Summer Blues Be Seasonal Depression?

Best Foods to Eat for Your Mood–and a Few Bad Ones

11 Simple, Proven Ways to Optimize Your Mental Health

Depression Relapse: What Can Trigger It and How to Prevent It originally appeared on usnews.com