Some of the more common factors involved in depression are:
Family's Medical History
Other psychological disorders. Anxiety disorders, eating disorders, schizophrenia, and (especially) substance abuse often appear along with depression.
These are all things you should look at, if any of these fit you then you should mention it to someone.
Types of Depression
Major Depressive Disorder
depression can be hereditary. See if it runs in your Family it could run in every generation or skip a few, but chances are someone in your Family has sufferede with it.
Trauma and stressful situations
Things like financial problems, the breakup of a relationship, or the death of a loved one, sexual, physical, or emotional abuse can trigger depression. You can become depressed after changes in your life, or serious tramatic event.
A low self esteem, Stress and Worrying
People who have low self-esteem and a negative outlook, if you are constantly worrying, stressed, and have anxiety you are at a higher risk of becoming depressed. Goes back to how your self esteem can effect your life in so many ways!
This type makes it hard to work, sleep, eat, and function as you normally would. It keeps you from enjoying the normal things that were once pleasurable,like hobbies, and work, everything becomes difficult and causes you to think about yourselve and the world in negative ways. Major depression is often disabling.
Dysthymic Disorder
A milder type of major depression. People with dysthymia may appear to be mildly depressed to the point that it seems to be a part of who they are. When you finally seeks help for dysthymia, it is not uncommon that you have struggled with this condition for a number of years.
Bipolar Disorder
Also known as manic-depression or manic-depressive disorder. This type effects your mood that one day you are depressed and then there are days you are hyper, extremely happy, invinciable, you can take on the world type of attitude, this is called mania. For people who have bipolar disorder, the depressions can be severe and the mania can seriously impair one's normal judgment. When in the manic stage you can also ,be prone towards reckless and inappropriate behavior such as having sex with anyone, anywhere, anytime, also spending tons of money you most likely don't have to spend. You may not be able to realize the harm of your behavior and actions and may even lose touch with reality.
Cyclothymic Disorder
A milder type of bipolar disorder. Your mood alternates between a less severe mania (known as hypomania) and a less severe depression. (This is the one I have)
Substance-Induced Mood Disorder
Depression may be caused by the use or abuse of substances such as drugs, alcohol, medications, or toxins.
Seasonal Affective Disorder (SAD)
This type effects people during the seasons of the year. During the winter months individuals feel depressed, but during other months their moods may be normal.
Postpartum Depression
A rare form of depression occurring in women within approximately one week to six months after giving birth to a child.
Premenstrual Dysphoric Disorder
This is very uncommon type of depression effecting a some menstruating women. You may feel depressed and irritable for one or two weeks before their menstrual period each month.