Depression is a mood disorder that causes a persistent feeling of sadness and loss of interest in things and activities you once enjoyed. It can also cause difficulty with thinking, memory, eating and sleeping. It’s normal to feel sad about or grieve over difficult life situations, such as losing your job or a divorce. But depression is different in that it persists practically every day for at least two weeks and involves other symptoms than sadness alone.

There are several types of depressive disorders. Clinical depression, or major depressive disorder, is often just called “depression.” It’s the most severe type of depression.

Without treatment, depression can get worse and last longer. In severe cases, it can lead to self-harm or death by suicide. The good news is that treatments can be very effective in improving symptoms.

Causes: 

Researchers don’t know the exact cause of depression. They think that several factors contribute to its development, including:

• Brain chemistry: An imbalance of neurotransmitters, including serotonin and dopamine, contributes to the development of depression.
• Genetics: If you have a first-degree relative (biological parent or sibling) with depression, you’re about three times as likely to develop the condition as the general population. However, you can have depression without a family history of it.
• Stressful life events: Difficult experiences, such as the death of a loved one, trauma, divorce, isolation and lack of support, can trigger depression.
• Medical conditions: Chronic pain and chronic conditions like diabetes can lead to depression.
• Medication: Some medications can cause depression as a side effect. Substance use, including alcohol, can also cause depression or make it worse.

Symptoms: 

• Loss of vision in one or both eyes due to inflammation of the optic nerve 
• Weakness that may be severe 
• Difficulty coordinating intended (voluntary) movement such as walking 
• Rapid onset of fever 
• Some degree of impairment of consciousness, perhaps as severe as coma

Treatment: 

Depression is one of the most treatable mental health conditions. Approximately 80% to 90% of people with depression who seek treatment eventually respond well to treatment.