There are many signs that it is smart to educate yourself to make yourself comfortable and knowledgeable when confronted with the symptoms
Depression is a mental health disorder, symptoms include loss of interest in hobbies and activities as well as a persistent depressed mood.
Depression Symptoms
One of the symptoms is trouble sleeping even though they often feel more tired and have troubles wanting to get out of bed or do anything; when people become depressed they have problems sleeping with many restless nights lying awake at night. They also have a decrease in finding joy in activities they used to love to take part in such as sports, family events or even hanging out with friends. Even though most people have a decrease in most of their energy you might see some drastic change such as them doing something really big like a big project or planning their death. Another sign to watch out for is change in appetite such as eating more or less then they normally do. Usually when people are depressed they can snap faster and get more irritable when things don't go their way. Substance abuse can also come with depression as kids turn to substances to try to feel anything again. The sudden rush of emotion they get when abusing something makes them more likely to become addicted and try more and more and even more dangerous kinds of substances. Usually when people become depressed they experience a feeling of nothingness or emptiness and have trouble making up their mind about things.
If you fear anything is serious and might lead to death call 911 or the suicide hotline.
Sources
https://www.prevention.com/life/a20465433/surprising-depression-symptoms/
https://www.everydayhealth.com/depression/symptoms/depression-symptoms-you-shouldnt-ignore/