9 Depression Symptoms You Should Never Ignore

If these red flags last more than two weeks, see a doctor.

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Depression may not be something you can physically see from the outside, but the mental health condition still leaves plenty evidence throughout a person’s life. “Depression affects the person’s entire world, whether it’s having a romantic relationship, friendships, or holding a job,” says Ben Michaelis, PhD, a psychologist in New York City.

Certain symptoms, like loss of pleasure in usual activities, are more obvious; others, like sleep problems, can be vague and trickier to ascribe to depression alone.

And what’s the difference between depression or just a bad mood or a slump? The symptoms of depression must be present every day for at least two weeks in order to be considered a depressive episode, according to psychiatrist Susan Samuels, MD, NewYork-Presbyterian Hospital and Weill Cornell Medicine. Otherwise, chock up those few lousy days as a string of bad luck (take care of yourself, but you can hold off on calling your doc). Here are the common depression symptoms patients may experience during a major depressive episode.

  • Persistent low mood

  • Difficulty with sleep (either too much or too little)

  • Loss of interest in the things you used to like (called anhedonia)

  • Overwhelming feelings of guilt or hopelessness

  • Lethargy, which can feel like fatigue or a lack of ambition

  • Difficulty focusing

  • Changes in appetite (either increased or decreased)

  • Feeling “slow” or easily agitated

  • Thoughts of self-harm or suicide

These depression symptoms may vary depending on the person and the type of depression they have. Learn more about the eight types of depression here.

What Causes Depression Symptoms?

Experts don’t know exactly what’s going on in the brain that causes depression symptoms. “We do know that serotonin is probably the predominant neurotransmitter or neurochemical involved in depression,” says psychiatrist Gail Saltz, MD, of NewYork-Presbyterian Hospital and Weill Cornell Medicine.

Serotonin is a hormone that both allows nerves to send messages to each other and causes blood vessels to narrow, according to the National Institutes of Health. It is one, but not the only, chemical involved in the onset of depression. When people are experiencing depression, their bodies don’t regulate these hormones correctly.

“There’s also some research indicating that people [who] are depressed have differences in their brain structure,” says Dr. Michaelis. “The white matter in their brain is structured somewhat differently.”

Depression affects 16.1 million U.S. adults, or 6.7 percent of the adult population, according to the National Institute of Mental Health. Specifically, the highest rates of depression occur in people between 18 and 25, and depression is more common in women than men (8.5 and 4.7 percent of the population, respectively).

Besides age and gender, these are common risk factors for depression:

  • A personal history of depression

  • A family history of depression

  • A personal history of another mental health disorder, such as anxiety or addiction

  • A stressful life event

Certainly, major life changes like losing a parent or getting laid off can trigger depression, but it’s important to realize that depression doesn’t need to have an obvious cause. It can strike without any major event at all. In fact, some people with depression may feel guilty because they feel they have no valid reason to be unhappy with their lives. “[Depression] is a real struggle,” says Nancy Snell, a patient with depression. “It’s not logical, and it doesn’t matter what you look like on the outside. My life is really, truly in technicolor, and yet it feels black and white to me.”

“There’s a biological process going on,” says Dr. Saltz. “It’s an illness. They can’t control it, [and] they really need treatment.” That treatment may include medication, therapy, or both. Find out more about the types of psychotherapy used to treat depression here.

Although many people try to “fight through” feelings of depression, getting a diagnosis can come as a relief.  Having an answer also means being closer to finding a solution, and many people with depression are able to manage symptoms and even recover to live more vibrant lives out of the fog of depression.