Perhaps one of the most common misconceptions about depression is that it’s a state of mind. In reality, though, depression, or major depressive disorder, is a serious medical illness, according to the American Psychiatric Association (APA). And a common one at that: According to the APA, it affects nearly one in 10 adults each year, and women are more likely to experience it than men.

Everything from a person’s brain chemicals to genetics and even environmental factors (think: exposure to violence, abuse, or poverty) can trigger depression. And according to the National Institute of Mental Health (NIMH), there are three common types of depression: major depression, dysthymic disorder or dysthymia, and minor depression, with the severity and duration varying among them.

Regardless of the cause or type though, one thing is consistent: Depression can seriously and negatively affect the way you feel, think, and act if gone untreated. So, it’s important to be able to identify if and when you may need to seek professional help.

So how do you distinguish signs of depression from signs of sadness? According to the APA, symptoms must continue for at least two weeks for them to be representative of depression. And, while sometimes sadness and grief can feel or seem a lot like depression, there are usually a few distinguishing factors.

For example, when people grieve, though they may feel intensely sad, those painful feelings tend to be intermixed with happy memories; and the circumstances don’t typically affect self-esteem. Those who suffer from depression are more likely to be void of positive thoughts or happiness, and to be void of self-esteem, according to the APA.

Dr. Stacey Rosenfeld, a licensed clinical psychologist who specializes in mood and anxiety disorders, also noted that a key differentiator is thoughts of suicide — if you experience any suicidal thoughts or notions, it’s important to seek help. Other common signs of depression, according to Dr. Rosenfeld are:

•Low energy
•Sleeping too much (or having insomnia)
•Not enjoying activities you used to
•Over- or under-eating
•Difficulties concentrating
•Feelings of hopelessness or worthlessness

You can also ask yourself a few key questions to help determine if you may be suffering from depression:

•“Is it difficult to get out of bed?”
•“Am I tired all the time?”
•“Am I able to enjoy parts of my life?”
•“Am I sad or crying more than usual?”
•“Am I having trouble concentrating?”
•“Do I not feel [like] myself?”

Even if you’re hesitant or unsure, the important thing is to seek professional help if you’re experiencing any of those symptoms or answered yes to most of those questions. Afraid to go at it alone? “Reach out to friends for help and support,” said Dr. Rosenfeld. Sure, it can be scary to talk about it, but remember that statistic: One in 10 people suffer from depression, so chances are the more you talk about it, the more people you’ll find who have been through something similar and are willing to help you.

READ MORE: What Are Natural Remedies for Depression?