What Is Depression And What Causes It?

January 25, 2024
written by:Claire Brandon, M.D.

Depression is a common but serious mood disorder that can severely affect the way you feel, the way you think, and the way you interact with the world around you. 

The precise cause of depression is unknown, but research suggests that a combination of genetic, environmental, psychological, and biological factors play a part. 

While depression can happen to people of any age, it most commonly begins in adulthood. 

Depression can also be influenced by and co-exist with serious medical illnesses like cancer, diabetes, and heart disease. Often, the presence of depression worsens the symptoms and conditions of these illnesses.

What Are Some Of The Signs And Symptoms Of Depression?

Everyone is different, and not everyone who is depressed will experience all of these symptoms. Some people with depression have many of the following symptoms, while others only experience a few. Symptoms can also vary in severity and frequency depending on the individual. 

Typically, the following symptoms of depression are experienced for most of the day, every day, for at least two weeks: 

  • Decreased energy
  • Sleep disturbances
  • Changes in appetite and/or weight
  • Loss of interest in regular activities
  • Irritability
  • Feeling sad, anxious, or empty
  • Feeling hopeless, or pessimistic
  • Feeling worthless or helpless 
  • Thoughts of self-harm or suicide

What Are the Subtypes of Depression?

Persistent depressive disorder or dysthymia

Characterized by a depressed mood lasting for two years or more.

Seasonal affective disorder (SAD)

Characterized by the presence of depression during winter months, and typical absence during spring and summer. Those with SAD typically experience significant changes in their life, including social withdrawal, changes in sleep habits, and weight fluctuation.  

Postpartum depression

Characterized by major depression during pregnancy or after delivery, including feelings of anxiety, exhaustion, extreme sadness, and difficulty completing daily tasks or care routines. 

Psychotic depression

Characterized by severe depression existing alongside some form of psychosis. Typically, psychotic symptoms are depressive in nature, including delusions of guilt or illness among others.

How is Depression Treated?

Typically, depression is treated with psychotherapy, medication, or a combination of the two.

There is no one treatment that will be right for everyone, so be sure to ask a qualified mental health professional about the best option for you. 

Making changes in your lifestyle can make a big difference in the way that you feel, and can have a positive impact on symptoms of depression. Being active and getting regular exercise, paired with eating a healthy diet that is rich in nutrients will supply your body with what it needs to start to heal. 

Although it can feel challenging, try to spend time with people that you trust. Isolation and depression often go hand in hand, but they don’t have to. Therapy can help you to educate yourself about what you’re feeling, how you can change the way you react to those feelings, and how you can start to feel better now.

Claire Brandon, M.D.

Dr. Brandon is a dual board-certified psychiatrist in both adult psychiatry and consultation-liaison psychiatry (treatment of psychiatric illness in medically ill adults). She completed her residency and fellowship training at Mount Sinai Hospital in New York City and did a second fellowship in public psychiatry at New York University in New York City

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