Depression can present different symptoms, depending on the person. But for most people, depressive disorder changes how they function day-to-day, and typically for more than two weeks. Common symptoms include:

• Changes in sleep
• Changes in appetite
• Lack of concentration
• Loss of energy
• Lack of interest in activities
• Hopelessness or guilty thoughts
• Changes in movement (less activity or agitation)
• Physical aches and pains
• Suicidal thoughts

Causes

Depression does not have a single cause. It can be triggered by a life crisis, physical illness or something else—but it can also occur spontaneously. Scientists believe several factors can contribute to depression:

• When people experience trauma at an early age, it can cause long-term changes in how their brains respond to fear and stress. These changes may lead to depression.
• Mood disorders, such as depression, tend to run in families.
• Life circumstances. Marital status, relationship changes, financial standing and where a person lives influence whether a person develops depression.
• Brain changes. Imaging studies have shown that the frontal lobe of the brain becomes less active when a person is depressed. Depression is also associated with changes in how the pituitary gland and hypothalamus respond to hormone stimulation.
• Other medical conditions. People who have a history of sleep disturbances, medical illness, chronic pain, anxiety and attention-deficit hyperactivity disorder (ADHD) are more likely to develop depression. Some medical syndromes (like hypothyroidism) can mimic depressive disorder. Some medications can also cause symptoms of depression.
• Drug and alcohol misuse. 21% of adults with a substance use disorder also experienced a major depressive episode in 2018. Co-occurring disorders require coordinated treatment for both conditions, as alcohol can worsen depressive symptoms.