What causes depression to manifest? Biology and sociological factors are the primary things to look at when trying to determine why you or someone you know may have a depression.

For the past generation psychiatry has what causes depression is an imbalance in the neurotransmitter serotonin.
Neurotransmitters are biochemical molecules in our brain involved in regulating mood. Serotonin is a well known neurotransmitter.
But, research is finding that serotonin, while still a player, isn‘t as important as we thought it was. [1]

Our behaviors and social stressors are also at play. What causes depression in one person may have no effect on another person.
For example, one person may have the social stressor of a job loss and manage to remain active and optimistic in a new job search while demonstrating no symptoms of depression, whatsoever.

Then, a second person experiences the same job loss but handles it very differently and gets depressed. The second person may have additional social stressors like a bigger family to support, or lower self-esteem.

Or, he or she may have a biological factor called a "genetic predisposition" which means his or her biology cannot withstand the stress of the job loss.
Therefore, the biochemistry falls out of balance negatively affecting important neurotransmitters that regulate mood.
If depression happens very early on in life, it is more likely to leave a lasting impact on later years, or even become chronic and worsen over time [2].
Further down you can read about what causes depression in teens.

Biological Causes of Depression

• genetics
• serotonin imbalance
• long-term presence of the stress hormone cortisol
• surplus of noradrenaline
• illness
• medications such as steroids and narcotics
• adrenal problems
• thyroid problems
• improper calcium levels
• anemia
• arthritis
• heart disease
• cancer
• viral infections
• liver infections
• brain infections
• Chronic premenstrual syndrome (PMS)
• Chronic pain

Social Causes of Depression

• social stressors
• the death of a loved one
• moving from one place to another
• financial problems
• relationship conflict
• career problems
• poverty
• living with someone who has serious medical problems
• drinking alcohol
• using illegal drugs
• having a substance abuse problem
• Recent childbirth (Postpartum Depression)
• fatigue
• learned beliefs of powerlessness
• racism
• homophobia

Causes of Childhood Depression

• Childhood trauma - emotional, physical or sexual abuse
• yelling or threats of abuse
• neglect (includes two parents working)
• criticism
• inappropriate or unclear expectations
• maternal separation
• family conflict
• divorce
• violence in the family, neighborhood or TV
• racism
• poverty [2]

Causes of Teen Depression

• normal maturation process
• sex hormones
• independence conflicts with parents
• disturbing events such as the loss of a loved one
• a breakup with a boyfriend or girlfriend
• failure at school
• low self esteem
• highly critical self-talk
• little sense of control over stressful events*homophobia

References