Genetic heredity, brain functioning, brain chemical substances or various physiological problems
Abnormalities in brain function: brain scans (MRI- Magnetic Resonance Imaging) reveal that certain brain regions, which are responsible for regulating emotions, thoughts, sleep, eating and behaviours, function abnormally in people with depression.
Chemicals imbalance in the brain: An imbalance of neurotransmitter – a chemical substance which transmits signals across the brain. For example, imbalance of the "happiness hormone", serotonin.
Changes in hormones: Hormones affect brain chemicals that regulate mood. Women are more vulnerable to depression due to hormonal changes during puberty, menstrual cycle, menopause and post-birth giving.
Heredity: Depression can run in family, yet this might not happen all the time, some people living with depression do not have a family history of depression. Research has pointed out that depression is an interaction between genetic and other environmental factors.