Depression is a mood disorder that causes a persistent feeling of sadness and loss of interest. Also called major depressive disorder or clinical depression, it affects how you feel, think and behave and can lead to a variety of emotional and physical problems. You may have trouble doing normal day-to-day activities, and sometimes you may feel as if life isn’t worth living.

More than just a bout of the blues, depression isn’t a weakness and you can’t simply “snap out” of it. Depression may require long-term treatment. But don’t get discouraged. Most people with depression feel better with medication, psychotherapy or both.

Although depression may occur only once during your life, people typically have multiple episodes. During these episodes, symptoms occur most of the day, nearly every day and may include:
Feelings of sadness, tearfulness, emptiness or hopelessness
Angry outbursts, irritability or frustration, even over small matters
Loss of interest or pleasure in most or all normal activities, such as sex, hobbies or sports
Sleep disturbances, including insomnia or sleeping too much
Tiredness and lack of energy, so even small tasks take extra effort
Reduced appetite and weight loss or increased cravings for food and weight gain
Anxiety, agitation or restlessness
Slowed thinking, speaking or body movements
Feelings of worthlessness or guilt, fixating on past failures or self-blame
Trouble thinking, concentrating, making decisions and remembering things
Frequent or recurrent thoughts of death, suicidal thoughts, suicide attempts or suicide
Unexplained physical problems, such as back pain or headaches
For many people with depression, symptoms usually are severe enough to cause noticeable problems in day-to-day activities, such as work, school, social activities or relationships with others. Some people may feel generally miserable or unhappy without really knowing why.
Depression symptoms in children and teens
Common signs and symptoms of depression in children and teenagers are similar to those of adults, but there can be some differences.
In younger children, symptoms of depression may include sadness, irritability, clinginess, worry, aches and pains, refusing to go to school, or being underweight.
In teens, symptoms may include sadness, irritability, feeling negative and worthless, anger, poor performance or poor attendance at school, feeling misunderstood and extremely sensitive, using recreational drugs or alcohol, eating or sleeping too much, self-harm, loss of interest in normal activities, and avoidance of social interaction.
Depression symptoms in older adults
Depression is not a normal part of growing older, and it should never be taken lightly. Unfortunately, depression often goes undiagnosed and untreated in older adults, and they may feel reluctant to seek help. Symptoms of depression may be different or less obvious in older adults, such as:
Memory difficulties or personality changes
Physical aches or pain
Fatigue, loss of appetite, sleep problems or loss of interest in sex — not caused by a medical condition or medication
Often wanting to stay at home, rather than going out to socialize or doing new things
Suicidal thinking or feelings, especially in older men
When to see a doctor
If you feel depressed, make an appointment to see your doctor or mental health professional as soon as you can. If you’re reluctant to seek treatment, talk to a friend or loved one, any health care professional, a faith leader, or someone else you trust.
When to get emergency help
If you think you may hurt yourself or attempt suicide, call 911 or your local emergency number immediately.
Also consider these options if you’re having suicidal thoughts:
Call your doctor or mental health professional.
Call a suicide hotline number — in the U.S., call the National Suicide Prevention Lifeline at 1-800-273-TALK (1-800-273-8255). Use that same number and press “1” to reach the Veterans Crisis Line.
Reach out to a close friend or loved one.
Contact a minister, spiritual leader or someone else in your faith community.
If you have a loved one who is in danger of suicide or has made a suicide attempt, make sure someone stays with that person. Call 911 or your local emergency number immediately. Or, if you think you can do so safely, take the person to the nearest hospital emergency room.
Source:https://www.mayoclinic.org/diseases-conditions/depression/symptoms-causes/syc-20356007