Depression is a serious mental health problem that causes a persistent feeling of sadness and loss of interest in activities. It affects how you think, feel and behave, and it can cause emotional, functional and physical problems. Although depression can occur at any time in life, symptoms may be different between teens and adults.

Regular sadness

Feeling moody, sad, or grouchy? Who doesn’t once in a while? It’s easy to have a couple of bad days. Your schoolwork, activities, and family and friend drama, all mixed with not enough sleep, can leave you feeling overwhelmed. On top of that, teen hormones can be all over the place and also make you moody or cry about the smallest thing. Regular moodiness and sadness usually go away quickly though, within a couple of days.

Depression

Untreated depression is a more intense feeling of sadness, hopelessness, and anger or frustration that lasts much longer, such as for weeks, months, or longer. These feelings make it hard for you to function as you normally would or participate in your usual activities. You may also have trouble focusing and feel like you have little to no motivation or energy. You may not even feel like seeing your best friends. Depression can make you feel like it is hard to enjoy life or even get through the day.

Symptoms of depression can include:

• Feelings of sadness or emptiness Inability to experience pleasure — even from activities that you used to enjoy
• Feeling worthless, guilty, or hopeless
• Isolating from others
• Physical ailments
• Fatigue
• Lack of motivation
• Irritability
• Indecisiveness
• Difficulty concentrating
• Changes in sleeping and/or eating habits
• Suicidal thoughts, feelings, or behaviors

It's not known exactly what causes depression. As with many mental disorders, a variety of factors may be involved, such as:

• Biological differences - People with depression appear to have physical changes in their brains. The significance of these changes is still uncertain, but may eventually help pinpoint causes.
• Brain chemistry - Neurotransmitters are naturally occurring brain chemicals that likely play a role in depression. Recent research indicates that changes in the function and effect of these neurotransmitters and how they interact with neurocircuits involved in maintaining mood stability may play a significant role in depression and its treatment.
• Hormones - Changes in the body's balance of hormones may be involved in causing or triggering depression. Hormone changes can result with pregnancy and during the weeks or months after delivery (postpartum) and from thyroid problems, menopause or a number of other conditions.
• Inherited traits - Depression is more common in people whose blood relatives also have this condition. Researchers are trying to find genes that may be involved in causing depression.

(Mayo Clinic)

There are various treatment options for depression. They include psychological treatments, medication and general measures such as relaxation techniques. Different treatment options are often combined.

Psychological Treatments

• Cognitive behavioral therapy
• Psychoanalytic approaches
• Systemic therapy

Medications

• Antidepressants
• Herbal products

Other Options

• Relaxation techniques and yoga
• Sports and exercise
• Light therapy
• Sleep deprivation therapy
• Electroconvulsive therapy