Depression is most often caused by the interaction of a number of factors that affect people in unique ways. Although the exact mechanism that causes depression is not fully known, the current thinking is that combination of biological, genetic, environmental and psychological factors causes specific changes in brain chemicals called neurotransmitters such as serotonin, norepinephrine and dopamine.
Neurotransmitters enable nerve cells or neurons to communicate with one another across synapses. When persisting for a longer period of time chemical imbalance in the brain can cause depression or anxiety. Serotonin plays an important role in the regulation of mood, sleep cycle and appetite control. Serotonin deficiencies can cause excessive feelings of sadness and anxiety, the sleep disturbances, irritability and obsessive-compulsive disorder. Low levels of dopamine and norepinephrine cause a person to feel tired, unmotivated and foggy-headed. Cortisol and other body hormones may also be altered in depressed people. This hormon is involved in the response to stress. In healthy people the level of cortisol is the highest in the morning and decreases during the day. In depressed people, the level of cortisol does not decrease as the day progress. Prolonged high levels of cortisol in the bloodstream can cause chronic stress and many other health problems.
Depression often runs in families and genetics is an important cause for depression. What is actually inherited is a vulnerability to depression. It means that if we have close relatives who are depressed we are not destined to become depressed.
Depression cause can sometimes be a major life change, when we are overwhelmed by stress and our adjustment mechanism is ineffective. Some risk factors include death or illness of close family members or friends, divorce, loss of job or move, physical, sexual or emotional abuse, financial difficulties or even getting married or becoming a new parent. Maternal stress during pregnancy, birth complications and traumatic events in childhood may trigger an early onset of depression.
Pessimistic people with low self-esteem are prone to depression. Other people can have many external disadvantages without being depressed. Some people may be depressed for no apparent reason. In such a case depression cause seems to be more biological.
Medical illnesses such as stroke, a heart attack, hormonal disorders, Parkinson's disease, diabetes, HIV, anxiety and eating disorders, schizophrenia, cancer or Alzheimer's disease often appear along with depression. Sometimes, depression is caused by medications used to treat medical conditions. Substance abuse (alcohol, nicotine and drugs) is a significant factor in depressive disorder.
Depression treatment can target biological (natural remedies and medications) or psychological (psychotherapy and self-help resources) causes.