Everyone experiences a range of emotions over the course of days and weeks, typically varying based on events and circumstances. When disappointed, we usually feel sad. When we suffer a loss, we grieve. Normally these feelings ebb and flow. They respond to input and changes. By contrast, depression tends to feel heavy and constant. People who are depressed are less likely to be cheered, comforted or consoled. People who recover from depression often welcome the ability to feel normal sadness again, to have a “bad day,” as opposed to a leaden weight on their minds and souls every single day.

Of people diagnosed with major depressive disorder, who are treated and recover, at least half are likely to experience a recurrent episode sometime in their future. It may come soon after or not for many years. It may or may not be triggered by a life event. After several episodes of major depression, a psychiatrist may suggest long-term treatment.

A wide variety of treatments have been proven effective in treating depression. Some involve talking and behavioral change. Others involve taking medications. There are also techniques that focus on neuromodulation, which incorporates electrical, magnetic or other forms of energy to stimulate brain pathways. Examples of neuromodulation include electroconvulsive therapy (ECT), vagus-nerve stimulation (VNS), transcranial magnetic stimulation (TMS) and the experimental deep-brain stimulation (DBS).

The choice of therapy should be guided by the nature and severity of depression, past responses to treatment, and the patient’s and family’s beliefs and preferences. Whatever approach is selected, the patient should be a willing and active participant, engaging in psychotherapy or regularly taking the medication, for example.

Total openness is important. You should talk to your doctor about all of your symptoms, important milestones in your life and any history of abuse or trauma. Also tell your doctor about past history of depression or other emotional symptoms in yourself or family members, medical history, medications you are taking — prescribed or over-the-counter, how depression has affected your daily life and whether you ever think about suicide.

If your symptoms are mild, do not impair your work or home life, or adversely affect your health, and you do not think about suicide or self-harm, you could wait a week or two before visiting a professional to see if the symptoms may improve on their own. But more serious symptoms need immediate attention.