What's your opinion on causes depression and anxiety?

Multifactorial. Causes of depression and anxiety can be multifactorial such as : having a positive family history , brain chemistry changes, medical illnesses (i.E thyroid disease), side effects from medications, major life stressors, substance use/abuse and history of abuse/trauma.
Anxiety. Usually in my experience a lack of empathy from caregivers who are limited in knowing how to foster a positive attitude in a child. This creates a negative self voice that can easily be carried into adulthood. Try reading my book, "changing your inner voice" featured on the soundmindz.Org website for more understanding. Best.