Causes of Depression

Vulnerability

On a biological level, vulnerability to depression appears to be closely linked to unnaturally low levels of serotonin and dopamine in the brain. Serotonin helps regulate our emotions, sleep as well as anxiety response. Not as much is known about dopamine, but it appears to modulate signals between neurons in the brain, making sure important connections are not lost to background noise. Depressed individuals often show very low levels of both.

These chemical levels may be linked to inherited traits, along with other biological vulnerabilities. Depression is known to run in families. Bipolar affective disorders, in particular, tend to appear across generations.

However, a purely biological approach misses a range of other factors that can put an individual at risk. Early sexual or physical abuse makes depression many times more likely. Brain damage from an accident or from a degenerative disease (such as multiple sclerosis), can affect the central nervous system in a way that makes an individual vulnerable. Certain viruses (such as HIV/AIDS) and some cancers may even have the same effect.

Triggers

Simply being vulnerable is not enough to bring on depression. What actually starts an episode of depression, or a long-running affliction? Often, but not always, a trigger event begins the downward spiral.

A trigger may be obviously emotional, like the death of a spouse or family member. Heightened emotions may be followed by a feeling of deadness, leading to depression. The time following childbirth is an equally well-known, but more mysterious source of depression for many women. It is thought that the huge hormonal changes that occur after a birth act as a trigger in a woman vulnerable to depression.

Alcohol and drugs may function as triggers. Alcohol appears to offer an escape from problems, but acts as a general depressant on the brain. It is unsurprising that alcoholism and depression are often closely linked. Many sufferers report that psychotropic street drugs like LSD and speed also have a trigger effect on their depression, usually in the �come down� phase the following day.

Specific illnesses may trigger an episode of depression. Chronic fatigue syndrome, for example, forces sufferers to give up many of the energetic activities that they enjoy. The resulting lack of exercise, stimulation, activity or social contact may precipitate an attack of depression.

Some individuals find that their depression is triggered by short daylight hours in winter. Known as seasonal affective disorder, the resulting depression is thought to be due to fluctuating melatonin levels due to lack of sunlight. However, in some individuals, the cause of depression remains a mystery.