What are the causes of depression in the first place?

Multiple causes: Causes include : family history of depression, medical illnesses (i.E hypothyroidism), neurochemical imbalance, side effects from medications, major life stressors, death/loss, substance use and history of abuse.

Possible causes: Depression can related to neurotransmitter imbalances in the brain (serotonin, norepinephrine, or dopamine), hormone imbalances (estrogen, testosterone, cortisol, thyroid), genetic predisposition to mood disorders, head injuries, dealing with major stressors to include loss, alcohol or drug use and may occur as a side effect to some medications.