Many people feel depressed from time to time: sadness about a failed relationship, unhappiness with work performance, and despair over financial troubles. In most people, these feelings subside after a short period of time. But when depression lingers for days or weeks at a time and begins to affect daily activities, it is considered a medical issue. Those with depression are unable to prevent their feelings from overwhelming them. Around 19 million people in the United States have major depression, which is chronic and can be debilitating if untreated.

There are several different types of depression that demand attention. Major depression interferes with a person’s daily life for an average of six months. Major depression can recur throughout a person’s life, causing constant symptoms. Atypical depression is a subtype of major depression. It contains similar symptoms as major depression, but adds a mood swing in response to good news. The short burst of positive feelings goes away quickly. Other symptoms include weight gain and oversleeping. Dysthysmia is long-term depression characterized by mild depression. Dysthysmia can last a minimum of two years, unlike the six-month cycle of major depression. Because the depression is mild, a person always feels down and out and expects this is just the way they are. Bipolar disorder is a depression with wild mood swings between manic and depressive.

The causes of depression are complex and no single cause has been pinpointed. It is likely that depression is the result of a combination of hereditary, psychological, and environmental influences.

The brain plays an important role in depression. Neurotransmitters in the brain help cells communicate with each other. When neurotransmitters are out of balance, it creates communication problems between cells. This imbalance can lead to depression along with pain in the body that cannot be explained.

A hereditary element suggests that depression can also run in families. A person’s environment can also trigger depression, including a tragic life event, the use of drugs and alcohol, or the use of certain medications that can cause chemical imbalances.

Neurons are cells in the nervous system that carry information through an electrical process. They are responsible for giving the brain the necessary information to regulate the body. Inside a neuron is a neurotransmitter, which ‘excites’ a nearby neuron through electrical impulses. The space between neurons, or synapse, allows neurotransmitters to pass from neuron to neuron. This transfer allows information to move through the nervous system.

Serotonin is a specific neurotransmitter in the brain associated with relaying messages regarding a person’s mood. When the brain fails to produce the proper amount of serotonin, it is believed depression and other problems associated with mood can occur. However, studies are unclear as to whether the lack of serotonin causes depression or if depression causes the lack of serotonin. 

A medication known as selective serotonin reuptake inhibitor is used to treat anxiety disorders. It works by blocking the absorption of serotonin in the brain, which leads to an excess of serotonin. The increase in serotonin improves mood, indicating that a low level of serotonin can lead to depression.

The limbic system is a group of several connected “structures” in the brain that is responsible for many emotions and specific reactions like “fight or flight.” The hippocampus, which is part of the limbic system, is responsible for forming new memories, including time and place. Without the hippocampus, information would never be stored. But it also plays a role in emotion.

Some studies suggest that depression may be the result of damage to serotonin receptors in the hippocampus. Some people with depression and anxiety disorders, such as post traumatic stress disorder, have a smaller hippocampus than a normal person, sometimes up to 20 percent smaller.

Gender plays an important role in the cause of depression. Women are twice as likely to have depression as men. The reason for this can be attributed to many factors including genetic, hormonal, life experiences, and psychological.

• Genetics: Depression can run in a person’s family. A gene known as SERT regulates serotonin in the brain. It has been identified as a hereditary gene linked to depression.

• Hormonal: Aside from serotonin, hormones specific to women can have an affect on brain chemistry. Girls typically show symptoms of depression earlier than boys because they reach puberty earlier. The changes of hormones increase the risk of depression, but cannot cause depression on their own. Women who are pregnant and women who have just given birth also experience hormonal changes. Depression after birth is known as postpartum depression.

• Life experiences: Women face similar stresses as men in life, but often they can be more magnified. Women dealing with money struggles, poverty, overload of work in and out of the home, or abuse (sexual and physical) can take a toll and contribute to depression.

• Psychological: Women who experience anxiety or develop eating disorders are also more likely to develop depression.