Depression can be caused by a variety of factors, including biological, environmental, and psychological. Biological factors such as changes in brain chemistry and hormones can lead to depression. Environmental factors such as major life events, stressful or traumatic experiences, or certain living situations can also contribute to depression. Psychological factors such as low self-esteem, negative thinking patterns, and an inability to cope with stress can also lead to depression. It is important to talk to a mental health professional to determine the cause of your depression and get the appropriate treatment.