There are many factors that can contribute to the development of depression, and the causes can vary from person to person. Here are ten of the most common causes of depression: Biological factors: Depression may be linked to an imbalance of neurotransmitters in the brain, such as serotonin and norepinephrine. Genetics: Depression can run in families and may be influenced by genetic factors. Environmental factors: Childhood trauma, abuse, neglect, loss, and other adverse life events can increase the risk of depression. Substance abuse: Alcohol and drug abuse can contribute to the development of depression. Chronic illness: Chronic medical conditions, such as heart disease, diabetes, and cancer, can increase the risk of depression. Hormonal changes: Hormonal changes, such as those that occur during menopause or pregnancy, can trigger depression. Medications: Some medications, including beta blockers, corticosteroids, and benzodiazepines, can cause depression as a side effect. Chronic stress: Chronic stress, such as that related to financial or relationship problems, can contribute to depression. Social isolation: Lack of social support, isolation, and loneliness can increase the risk of depression. Seasonal factors: Seasonal affective disorder (SAD) is a type of depression that occurs in the fall and winter months and is related to the reduced amount of sunlight exposure.