Sometimes when you’re out on the road, it may be difficult to tell the difference between a few fleeting feelings of loneliness or sadness and a bigger issue like depression. Those sad feelings are part of being human, and they generally go away within minutes, or days at the most.

But when a person has a depressive disorder, it interferes with normal, everyday life. According to the National Institute of Mental Health, while depression is a fairly common illness, it is also serious, and most who experience it require treatment to get better.

The good news is most people who seek treatment can get better. So how do you know if what you are feeling is depression? Not everyone experiences it the same way, but here are five common symptoms:

You feel persistently sad, anxious or “empty.” You may also feel hopeless or pessimistic or experience feelings of guilt, worthlessness or helplessness.

You experience disturbed sleep patterns that may include insomnia, waking early in the morning and being unable to return to sleep or excessive sleepiness. This can lead to irritability, restlessness, fatigue and decreased energy.

You lose interest in activities or hobbies once pleasurable, including sex, and have difficulty concentrating, remembering details and making decisions.

You experience physiological symptoms, such as persistent aches or pains, headaches, cramps or persistent digestive problems. You may also find yourself overeating or lacking appetite.