As a personal observation, sometimes depression is a mystery and finding the cause isn't quite as easy as going through a list and applying a cure. Positive relationships including people who speak the truth in love and believe the best about you (even when given reason to believe otherwise) are crucial to mental and emotional health. That's the power of an environment of grace. A therapist I know defines mental health as "a relentless commitment to reality". Nevertheless, depression is an increasing issue warranting new medications and treatments that emerge every year.

According to Webmd.com and mayoclinic.org there are many factors that contribute to depression.

Abuse - Whether it’s physical, sexual, spiritual, or emotional, any abuse can trigger moments of anxiety or depression throughout a person’s life.

Medications - There are some drugs that can, as a side effect, can increase your risk of depression.

Conflict - If you’ve ever been in a situation where you were at odds with a friend family member, or coworker, you understand this one.

Death or Loss - Natural sadness or grief can make you especially vulnerable to ongoing depression.

Genetics - If you have a family history of anxiety you may face some challenges with depression yourself. This may be due, however, to both an issue with genetics as well as the environmental condition of a home or family during crucial formative years.

Major Events - Even good events such as a new job, graduation, or a wedding can trigger depression. Other events may include moving, losing a job, divorce or breakup, or retirement.

Illness - Often depression co-exists with dealing with a major illness or it can also be a response to an illness even after recovery.

Substance Abuse - Addiction to substances (drugs/alcohol) that cause a lack in one’s capacity to be in control of their urges, thoughts, or desires can trigger depression.

Secrets - Laurel Dewey's quote, "You're only as sick as your secrets" is an interesting key to unlocking the often hidden factor that torments so many people. When there is depression present and none of the common symptoms seem to be the source, a good question to ask someone you love is, "Is there anything you haven't told me?" As terrifying as it may be, that very question may be the very hurdle over which there is tremendous freedom.

“Researchers have noted differences in the brains of people who are depressed as compared to people who are not. For instance, the hippocampus, a small part of the brain that is vital to the storage of memories, appears to be smaller in people with a history of depression than in those who've never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is a calming brain chemical known as a neurotransmitter that allows communication between nerves in the brain and the body. It's also thought that the neurotransmitter norepinephrine may be involved in depression.
Scientists do not know why the hippocampus is smaller in those with depression. Some researchers have found that the stress hormone cortisol is produced in excess in depressed people. These investigators believe that cortisol has a toxic or poisonous effect on the hippocampus. Some experts theorize that depressed people are simply born with a smaller hippocampus and are therefore inclined to suffer from depression.
One thing is certain -- depression is a complex illness with many contributing factors. The latest scans and studies of brain chemistry that show the effects of antidepressants help broaden our understanding of the biochemical processes involved in depression. As scientists gain a better understanding of the cause(s) of depression, health professionals will be able to make better "tailored" diagnoses and, in turn, prescribe more effective treatment plans.”

The primary causes for depression and anxiety disorder are abuse, medications, personal conflict, death or a loss, genetics, traumatic events, personal problems, illness, and substance abuse. The concept of abuse can be seen as physical, sexual or emotional trauma. Medications can also causes depression as they may mix negatively with your body’s chemical make-up to increase your risk of depression. Personal conflict can result from any dispute you have with someone close to you or from an event that has considerable value on your quality of life. Death to someone close to you can also result in depression. Genetics can also contribute to depression, as family history can predispose you to depressive behavior. Traumatic events can range from positive and negative experiences, but depression can result from any major life change. Personal problems from mental illness, shyness, or not being accepted into a family or social group can lead to depression. Illness is another major cause of depression, as it may be a reaction to the illness itself. Finally, substance abuse has been known to be a major contributor to depression, as they dramatically alter a person’s lifestyle.

Depression and anxiety can occur when there are unexpected unfortunate events in a person’s life. These can be sudden death of a family member or loved one, failure in a class, relationship that did not work out, not getting the work that you wanted or a friend who suddenly leaves for a faraway land. In these circumstances, it is normal to become depressed. You will always need a trusted person to talk to and ease out your pain.

Depression and anxiety are the results of a lot of factors and can be beaten with strong will. It takes a lot of guts and confidence to be able to fight your depression and anxiety. The factors that cause these are experienced and not visible. They should be fought.