But if normal activities and tasks become impossible, if you're drinking more alcohol or taking drugs to numb feelings of sadness or guilt, or if you feel hopeless or even suicidal, you're probably suffering from more than a normal, limited-term case of the blues. But the red flags are persistence of symptoms and an inability to function normally as a result. For instance, a person who loses a job may well feel angry, sad, frightened, or guilty for several weeks or even longer. Just as you wouldn't expect to be able to recover from most diseases without medical intervention, you shouldn't assume that persistent depression will go away on its own. There is still a physiological component to those illnesses, and we manage those with medication, but we also need to help patients manage the stress in their lives so they have better control of their illness.
Depression is no different.
There are psychological and physical components to the illness. That's where it's different from a normal grief reaction. Clinically depressed people have lowered levels of serotonin and norepinephrine, two chemicals that help regulate mood, energy, and ability to concentrate. Simply put, because of this imbalance, they're physically unable to feel happier or to function normally. Yes, say experts.